LA26 PROGRESS REPORT
A) Abstract The Project was initiated analyzing the actual climate variability impact on the RP in order to understand the forcings acting in the RP water level, and to calibrate modeling tools. It was found a southward shift of the southwestern border of the South Atlantic high during 1950/2000 and a consequent increment of the eastern wind component. This is consistent with the observed annual and seasonal water level trend and with model sensitivity to the wind field. In addition, statistics of the most important patterns of the low-level atmospheric circulation associated to floods in the RP coast indicate a trend toward more frequent and intense synoptic systems.
A hydrodynamic model of the RP was developed and it is being calibrated and validated. A high- resolution regional model of the atmosphere was adapted for its use in the RP region. Climate features, relevant to the RP dynamics (wind and precipitation fields), are well simulated by some General Circulation Models. Thus, an ensemble of climate scenarios for the next hundred years in the RP region is being developed.
It was started a communicative process with relevant stakeholders aiming to its involvement throughout the Project development. PROGRESS REPORT
B) Report on the Tasks Scheduled to begin in the January-July 2002 period Task numbers according to the working plan. In brackets the end date of the working plan. We become aware for the need of two additional tasks. One of them, task 0, was necessary to assess the need and detail of the programmed tasks 2, 13 and 20. Task 0 is a sensitivity analysis of the water level in the Río de la Plata to discharges from tributaries and wind. The other additional task was originally planned for June 2003 as task 31, but it was initiated earlier since it was necessary for implementing task 24
0. Sensitivity analysis of the water level of the Rio de la Plata to the discharge from tributaries and wind The purpose of this task was to assess how important are these aspects in order to evaluate the effort that should be devoted to the understanding of present and future variability and change of the wind field over the Rio de la Plata (RP) and the neighboring ocean. Similarly, with the variability and change of the precipitation over the basin of the RP. Since these are very complicated issues that will hopefully be completed as part of the objectives of the Project, a numerical model of the RP was used as an approximate tool. This is the RIO DE LA PLATA 2000 model (Jaime & Menéndez 1999), a two- dimensional hydrodynamic model based on software HIDROBID II (Menéndez 1990). The domain of the model extends from the river head down to its mouth, considered to be the imaginary line that links San Clemente del Tuyú, in Argentina, with Punta del Este, in Uruguay. The model is already calibrated and validated (Jaime & Menéndez 1999) Runs were undertaken for a period of 5 days. The base run, coded as B0, was performed considering a situation of absence of winds (purely astronomical tide) and discharges of the tributaries (Paraná Guazú, Paraná de las Palmas and Uruguay Rivers) equal to their annual mean. The following stations were taken for control: San Fernando, Martín García, Buenos Aires, Colonia, La Plata and Montevideo Results and references are summarized in Annex B1.
In spite of the limitations of the model, it is possible to conclude, in general terms, that strong changes in the discharge from the tributaries are going to produce changes of the order of 10 to 20 cm in the so-called interior of the RP. This is comparable with an expected mean sea-level rise of about 60 cm. in certain scenarios, which will probably propagate almost entirely into the RP.
Regarding the winds, the model underestimated the response in water level because it runs only in the limited area of the RP itself. This aspect is being solved in the new version of the model, task 8. In spite of this and according to experiments described in Annex B1, an increase of 10 to 20 Km/h in the SE winds will produce a change of the order of 10 cm, at least.
1.Compilation of precipitation data of the Rio de la Plata basin Point 2 of the Joint Document (February 2002) This activity was completed, and data from Argentina were sent to the Project LA 32
2.Surface wind estimates download from NCEP/NCAR reanalysis. Climatological fields (March 2002)
1 The seasonal mean fields of the winds and geopotential at 1000 hPa were calculated using NCEP/NCAR reanalysis. The region includes the Río de la Plata (RP), and it can be seen in the figures of Annex B2.
2.1 The circulation over the RP is under the influence of the southwestern border of the South Atlantic high (SAH). This circulation shifts southward from winter to summer and northward from summer to winter. This implies a stronger westward component in summer than in winter (Fig. 1 of Annex B2). As a consequence, the mean high of the water levels should be greater in summer than in winter in the Argentine coast of the RP estuary This was confirmed by the analysis carried on as part of task 3
2.2 There was a shift southward in the circulation associated to the southwestern border of the SAH. It was more evident in summer, important in the transition seasons, and almost negligible in winter, and as a result of the westward component of the wind over the RP. This is consistent with results found under task 3 (See Figs. 2 and 3 of Annex B2)
2.3 Principal component analysis (PCA) performed on the seasonal geopotential fields confirms the southward shift of the mean seasonal circulation. There was a significant increment of the variance explained by the second mode, more associated to the summer circulation and the westward component of the wind over the RP from the 1950/60 decade to the 1990/00 one. At the same time, there was a significant reduction of the first mode, more associated to the winter circulation during the same period. The third mode, potentially associated to floods in the Argentine coast, also increased during this period (See Fig. 4 of Annex B2)
3. Compilation of cartography, satellite images, air photography and urban information (April 2002) Information gathered: The graphic information corresponds to the following departments in the Buenos Aires Province San Nicolás, Ramallo, San Pedro, Baradero, Zárate, Campana, Tigre, San Fernando, San Isidro, Vicente López, Avellaneda, Quilmes, Berazategui, Ensenada and Berisso, and the Federal District:
- Topographic Charts of the Geographic Institute Scale: 1:50.000, 22 charts. Scale: 1:100.000, 5 charts. Scale: 1:250.000, 4 charts. Scale: 1:500.000, 3 charts.
- Geodesy Map- Province of Buenos Aires: Metropolitan area, 1993; scale: 1:100.000.
- Satellite Images LANDSAT 5 TM. 226/ 083, Date: 30/03/1997 226/ 083, Date: 01/03/1998 225/ 084, Date: 15/09/1997
- Aerial Photos from the Argentine Hydrographic Service Flight Rosario- Punta Piedras; track: n° 3; Photos: 069 -070-071–072; scale: 1:40.000; Date: June 1991, lowlands of the Department of Tigre.
2 4. Analysis of the tide dynamics in the Rio de la Plata (April 2002) The features of the Tides on the Atlantic coast of Argentina and Uruguay and its propagation in the RP were reviewed in a short course. A short resume of the course follows: Classification of waves in the Sea according to their period Tide recording. Mean sea level Storm waves Astronomic waves Different methods for measuring tides Dynamic of tides Tide regime Statistical study of tides in the RP
The course was lectured by Ing. D' Onofrio and the participants were Dr. V. Barros, Dr. A. Menendez, Dra. M. Doyle, Dra. M. González, Dr. G. Escobar, Ing. M. Re, Lic. M. Fiore, Dr, J Codignotto , Dr. R. Kokot and D. Rios
As it was already found in previous studies, the mean level of the Buenos Aires port presented a positive trend during the last century. The new fact is that this trend was present in all seasons, but with consistently more high in summer and less in winter throughout the twentieth century (See item 3 of Annex B4). It was also prepared tide data for the Samborombón bay for further geological analysis of its coast (see item 6 of Annex B3).
5. Procurement of social data and cartographic information. Analysis of satellites images (May 2002) Socioeconomic information: In addition to the information used in the elaboration of the vulnerability index for the Buenos Aires fluvial littoral, all the information of public access, -by departments and for the Federal District, from the 1991 CNPyV (National Census of population and housing) and also the preliminary results from 2001 Census was compiled. These censuses are the only source for quantifying and analyzing the complex changes experienced by the Argentine population in its socioeconomic structure and its spatial distribution in the course of the last decade. The areas selected, which correspond to study cases are La Boca neighborhood in the Federal District and Avellaneda Department in the Greater Buenos Aires as examples of situations in big cities (see the following table), and the General Lavalle Department, as an example of rural environments and tourist services.
Urban Study Cases: Preliminary Results From The 2001 Census CNPyV 2001 DISTRITO IV (LA PARTIDO DE Preliminary Results BOCA) AVELLANEDA Total population (inhabitants) 84.144 344.199 Area (Km2) 10.5 55 Density (inhabitants/ Km2) 8.013,7 5993.4 Number of households 30.614 101.578 Population in households 83.273 327.910 Collective institutions 107 89 Population in collective inst. 871 1.728
3 Since the strategy is to work in three focalized areas were the impact of climate change is suspected to be greatest, satellite analysis is not initially considered necessary for the social analysis
6. Initial presentation of the Project and its objectives through interviews with stakeholders (May 2002) The types of interrelation between researchers and stakeholders can be: 1. CONSULTATION: Stakeholders are informants; they supply the information the research needs. The work plan is closed. 2. INTER-CONSULTATION: Stakeholders are informants and users as well; they give information and make suggestions about research needs and about their own needs (to which the research could give some answers). The work plan is permeable. It is possible to identify two kinds: 2.1 The stakeholders are still outside of the project design, with partial involvement through its development. 2.2 The stakeholders are included in the project development from its formulation. 3. NETWORK ASSOCIATION: Stakeholders include researchers. Participatory planning methodologies are used to build knowledge. The work plan is strategic.
In our case, we are working with the Type 2.1: Inter-consultation with stakeholders, with a previous project design. This component aims at achieving an inter-consultation relationship between: A – project members and the selected organizations (outside the project). B – project members among themselves (inside the project). C – project members of LA26 and others LA’s AIACC.
The aim of the methodology to be applied is to install a communicative process, that is to say, to go beyond isolated consulting by establishing regulated and continuous mechanisms of association and interchange with stakeholders during the development of the project.
At the same time, a process of interaction with the project LA26 team members will be set in order to assess a way of including the results of this inter-consultation in the adjustment of tasks and goals, and in the proposal of future projects.
The criteria for the selection of stakeholders was the following: Pertinence and previous experience in the research subject/ problem. Different institutional associations (public/ private, administrative levels, objectives). Opportunity, previous contacts and will.
A table with the preliminary selection of stakeholders is presented in Annex B4. We have already begun with the inter-consultation process with the first four stakeholders selected. At the same time, and always following the selection criteria, we have incorporated two new stakeholders to the inter- consultation process.
Finally, a brief of the research project is being prepared in order to facilitate the discussion with stakeholders.
7 Implementation of ETA model (May 2002)
4 The limited area Eta model (see Model description in Annex B5) was implemented in the Department of Atmospheric Sciences of the University of Buenos Aires with the help of consultant O. Frumento. The use of this model in the Project is to provide high-resolution wind fields to the hydrodynamic model. This is necessary for the study of extreme windy conditions that give rise to floods in the RP
A two-week training course on the theoretical grounds of the model and its practical use was developed. The training course was intended for graduate or advanced students of atmospheric sciences or similar disciplines. The Participants were: Dr. Rubén Bejaran (Departamento de Ciencias de la Atmósfera y los Océanos) Dr. Moira Doyle (Departamento de Ciencias de la Atmósfera y los Océanos) Dr. Gustavo Escobar (Departamento de Ciencias de la Atmósfera y los Océanos) Mr. Carlos Zotelo(undergraduate student) Miss Romina Mezher (undergraduate student)
As application for the Project, the following activity was undertaken: Simulation of five selected extreme events of southeast winds over the Río de la Plata estuary (Flood situations). Daily NCEP Reanalyzes were used to construct the input data to the ETA model. Results were checked with independent observations. These events combine different types of synoptic situations that lead to highest water levels in the RP (Found in task 15) with different astronomic tides (Found in Task 9). Outputs of these runs are being used now for the final calibration of the Hidrobid II model (task 8). More details in Annex B5.
8. Development of a large-scale version of the HIDROBID II model (June 2002) The inclusion of the maritime front within the hydrodynamic model domain will allow simulation of the generation of storm waves and the effect of the mean wind outside the RP on its mean level. The extended model is comprehended between latitudes 40.5°S and 32.4°S and longitudes 61.5°W and 51.5°W.
The National Hydrographic Service (SHN) provided the bathymetric data. The boundary conditions for the model are the discharge of the Río de la Plata tributaries at its head and the tidal wave front that penetrates through the southern border. The calibration consisted in obtaining a satisfactory agreement between the water levels as predicted by the model and as provided by the Tide Table at six different control stations (Monte Hermoso, Mar del Plata, San Clemente, Buenos Aires, Martín Garcia and Montevideo). Details in Annex B6.
9. Extreme surge analysis (June 2002) It was determined the greatest storm tides in the port of Buenos Aires for the period 1950-2000. Data from different sources were combined and consisted. From the observed highs were subtracted the astronomical predicted tide. Details on the data and on the methodology followed are in item 5 of the Annex B3
10. Photo interpretation of dry, normal and flood events (Scale 1: 20 000 and 1: 60 000) (June 2002). This task was planned within the framework of the construction of a topographic map in the Samborombón Bay with enough resolution to capture the possible future intrusion of water in the coastal areas. Therefore, this task and other connected to it are reported in this point.
5 Cartography, satellite images, air photography and urban information. Air photographs of Bahía Samborombón between Punta Piedras and Punta Rasa were obtained from the Naval Hydrographic Survey on a 1:40.000 scale. Topographical maps on a 1:50.000 and 1:100.000 scales were obtained from the Geographic Institute. Likewise, Landsat 5 and Landsat 7 satellite images were obtained from the National Commission of Spatial Research.
Photo interpretation of dry, normal and flood events was started in the coastline of the Samborombón Bay, Buenos Aires Province. This task enabled us to identify the coastline and the inter-phase area over an extensive marsh zone of difficult access. On the basis of this information, we are working on the base map that will be completed with field-work (task 12 of work program: topographic measurements and fieldwork will be carried out to produce detailed altitude level maps of coastal areas subject to possible floods).
It is being recognized outcrops and geomorphology units in the coastline of the Samborombón Bay, Buenos Aires Province. In this work phase, unit recognition was made with air photographs on a 1:40.000 scale and with Landsat 5TM (Thematic Mapper) satellite images. These images have a 30-m spectral resolution and sensors in 7 spectral bands that include from the visible to the thermal infrared zone. Information obtained from satellite analysis allowed us to monitor the wetlands and all the other geomorphology units. Digitization of coastline and of the most important topographic features from cartography on a 1:50.000 scale is being made with the following characteristics: contour lines with 5-m. equidistant, real scale of work in Gauss-Krügger coordinates. Tasks of edition are made with AutoCad 14 over digitized information (DWG digital format) and assembling of the area topographic mosaic with its corresponding references with AutoCad 14 in DWG digital format.
11. Data base construction, in a GIS environment. Point 3 of the Joint Document (July 2002) From the information obtained in the Workshops in Nairobi and Trieste, we detected the need to incorporate specific technical support on account of the complexity of the task. Consequently, we have contacted an expert in a GIS applied to the assessment of environmental risk who will join the team during the next semester. This activity will be funded with collateral funds.
Anyway, we have already produced socioeconomic and demographic information in GIS format. This information is related to the indicator used for the construction of a vulnerability index for the study area based on Census 1980 and 1991 provided by INDEC. Total Population (1980 and 1991) Relative population variation between 1980 and 1991 Population Density (1980 and 1991) Young potential dependence index (1980 and 1991) Elderly potential dependence index (1980 and 1991) Percentage of households and population with unsatisfied basic needs (1980 and 1991) Percentage of NBI households with three and more indicators of deficiency (1991). Percentage of households with woman in charge (1991). Total child mortality rate (1991) Neonatal mortality child rate (1991) Percentage of population without access to social security (1991)
6 Total unemployment rate (1991).
Such indicators were processed using the Arcview Software. Additional information on the study area available in digital format is:
- Land use (1997-98). - Transport (railways, roads and highways). - Main cities in the area. - Boundaries.
12. Topographic measurements and fieldwork will be carried out to produce detailed altitude level maps of coastal areas subject to possible floods (July 2002) This task is starting in July 2003.
13. Election of future climate scenarios in cooperation with Project L32. Point 6 of the joined document (July 2002) Results of task 0 indicate that the mean water level of the RP responds to the wind field and to the discharge of its tributaries. According to geographic and geological experience, sea level rise is going to considerably influence the water level of the RP. Therefore, the variables required from climate scenarios are surface mean winds over the RP and the outer adjacent ocean, and mean precipitation over the La Plata Basin. Surface winds are not a standard output of the GCM scenarios. However, this variable is strongly coupled with sea surface pressure (SLP) fields. Consequently, wind scenarios are going to be developed through SLP scenarios.
After their participation in the Norwich workshop, I Camilloni (LA26) and M. Bidegain (La 26 and LA32) analyzed the SRES-A2 scenario runs of the Modelle and Daten (MOD) page of IPCC (www.dkrz.de/ipcc/ddc/html/SRES/SRES_all.html). This page has only 4 models available:
· HADCM3 (Hadley Centre-UK) · CSIRO-Mk2 (CSIRO-Australia) · NCAR-PCM (NCAR-USA) · CGCM2 (CCCma-Canada)
Model outputs of SLP in the area defined by the latitudes 20°S to 47°S and the longitudes 45W° to 67°W for the period 1950-2000 (or periods within these dates according to model outputs) are being compared with NCEP/NCAR reanalysis for annual as well as monthly mean fields. The SLP field in the region containing the RP is largely dominated by the southwestern border of the South Atlantic high (See Annex B2). These features are very well simulated by the HADCM3, both in the annual field and in its seasonal evolution. The CSIRO-Mk2 exhibits a good performance in these aspects, though not as good as that of the HADCM3. On the other hand, the NCAR-PCM and the CGCM2l simulations of the SLP in the region are far from the observed climatology. Regarding precipitation in the RP basin, results are similar to those obtained for SLP (See Annex B7 for details).
To complete the evaluation of the models, at least 3 other models will be considered, as soon they will be available from the Modelle and Daten (MOD) page of IPCC or from other sources. After that, an
7 ensemble of the future scenarios of the 3 or 4 models that best reproduce SLP and precipitation in the region of interest will be constructed.
15 Study of weather storms over the region affecting the RP area of the period 1944-2000 using NCAR/NCEP reanalysis. Study of frequency and strength of these systems and of their seasonal and interannual variability and of their trends or decadal variability (August 2002) 15.1 Data A subset of high water level events was prepared following these criteria: -Records of water level at the port of Buenos Aires for the period 1951/2000. -Every register was decomposed in its astronomical tide component plus the meteorological component -The subset was formed with the cases when the meteorological component was higher than 2.73 m for at least 24 hours. This latter requirement permitted to select only those cases that represented floods or near flood conditions along the coast of the Province and city of Buenos Aires.
72 cases meeting the aforementioned requirements were selected. These events are present throughout the year, but with greater frequency in summer and a lower frequency in winter. When they are counted by decades, they present an increased trend (Annex B8).
15.2 Atmospheric low-level circulation fields The composite associated to the 72 cases indicates that the geopotential 1000 hPa features are dominated by a high pressure system with center at about 800 Km to the southwest of the RP. This field favors the southeasterly winds over the RP and the neighboring ocean. These cases also present a trend toward a more intense pressure gradient over the RP in the 1950/2000 period. (Annex B8)
15.3 Variability of the associated low-level atmospheric fields Principal component analysis of the geopotential fields associated to these 72 greatest water levels shows that three modes account for more than 75 % of the variance. The first mode represents the case of a migratory anticyclone that when centered west of the RP induces southern winds over the river. The second mode represents the case of a very deep perturbation of the mean flow with a strong and huge anticyclone entering from the southern tip of the continent. In these cases, the anticyclone migrates slower than the average anticyclones and favors the south to southeast wind component over the RP. Finally, the third mode is typical of a cyclogenesis north of the RP, and it produces the more intense southeasterly winds over the RP. (Annex B8)
16. Development of future scenarios for the Paraná delta growth (August) This task was not formally initiated in the framework of the Project, but information has already been developed in other Project headed by Drs. Menendez and Codignotto. In the second semester this information will be adapted to the Project needs.
20. Estimate of extreme streamflow events. Statistical approach based on historical data and a conceptual approach based on the relationship of rainfall and discharge with SST in the sub- basins. In the Paraná River: (October 2002) The greatest discharges of the main tributaries of the RP, the Paraná and the Uruguay rivers and its climatic forcings were studied. The summary of the main results is as follows.
8 Floods in the Uruguay River Because of its size, its narrow transverse section and the step terrain the lag between the river discharge and rainfall takes few days. The main discharges are usually caused by synoptic events or by a short succession of them. Inspection of each of these events showed that all follows a week of a similar dominant low-level circulation (Fig 2 of Annex 9)
The greatest discharges of the Paraná River The high streamflows in the Middle Paraná causes floods over large areas of the Lower Paraná even without a significant local contribution in this sub basin. Due to the large size of the Paraná basin, its big discharges and floods persist for months and are not caused by single synoptic events. The greatest monthly-averaged discharge anomalies of the twentieth century at Corrientes (the outlet of the Middle Paraná) calculated with respect to the 1931-80 monthly means are shown in Table 1 of Annex B9. With few exceptions, the major discharge events in the Lower Paraná originates in the Middle Paraná basin, more precisely in the upper part of this basin. The six greatest peaks occurred during El Niño events and five of them in the autumn of the year following the beginning of the events.
22. Consultation about demands and communication of Project partial results with stakeholders through mail and email. (November 2002) Regarding Task 6, we are maintaining e-mail contact with the stakeholders. At the same time, some stakeholders have invited members of the team to participate in their own activities. For example, the City Foundation, which is organizing a participatory consulting process on the environmental problems of the Matanzas–Riachuelo river, has incorporated team members as consultants, and they have been invited to participate in a Workshop that will be held in September.
31. Develop scenarios of strong waves (June 2003) The main characteristics of wind waves in the outer region of RP have been assessed by means of a statistical analysis of wave data measured by Hidrovía S.A. with a directional wave recorder Datawell Waverider. The instrument was moored at approximately 35° 40’ S and 55° 50’ W. This data set represents the single one existing for the RP. The frequency separating the "Swell" and "Sea" conditions is approximately 1/6 Hz (T= 6 sec.).
As a result of this initial analysis, it can be seen that swell and sea conditions are clearly identified in the outer region of RP. More details are supplied in Annex B10. Both conditions must be considered in order to evaluate the mean wave parameters on the coast of Buenos Aires.
Given the geographical position of the RP and its general NNW-SSE orientation, only the waves with E, SE and S directions are able to propagate from the mouth (outer region) to the inner region of the RP. However, swell and sea conditions propagating from the mouth will be highly attenuated by refraction, shoaling and dissipation by bottom friction. Therefore, the next step in this study will be to propagate the obtained sea and swell conditions from the outer region towards the inner region of the RP, and evaluate how heights and directions will be transformed. In order to do this, a numerical model that computes refraction, shoaling and energy dissipation by bottom friction will be implemented.
TRAVEL ACTIVITIES
9 The PI of the Project, V. Barros and the Co-PI, C. Natenzon and A. Menendez participated in the AIACC kick-off workshop held in Nairobi during February 2002.
I. Camilloni participated of the Norwich workshop on Climate Scenarios, during the month of April. She prepared a presentation, but it was not presented because only one presentation by region was made. The power point presentation is attached in Annex F1
The Co-PI J. Codignotto,. M. Ré and J. Barrenechea participated of the Trieste workshop in June. They made a presentation that is attached in Annex F2.
The Co-PI C. Natenzon was invited to the Trieste workshop in June and made a presentation that is attached in Annex F3
The PI of the Project V. Barros made in January a short trip to Montevideo to plan the recommended (By AIACC) joint activities with Project LA 32. He made another short trip in June to Montevideo to coordinate the development scenarios activity with M. Bidegain (Task 16) and to work with M. Caffera in the extreme discharges of the Uruguay River (Task 20)
The Co-PI M. Caffera made in June a short trip to Buenos Aires to work with I. Camilloni and V. Barros in the extreme discharges of the Uruguay River (Task 20)
The Co-PI and also investigator of Project LA32 M. Bidegain made in June a short trip to Buenos Aires to work with I. Camilloni in the development of Climate scenarios (Task 16). This activity was funded by Project LA32
After the Norwich workshop on Climate Scenarios, at a requirement of Project LA 27, there was a meeting in Buenos Aires to agree in the use of common climate scenarios for all the Projects involved in the region, namely southern South America. The participants were M Bidegain for Project LA 32; O. Cantina, G. Margin, M. Travaso, J. Castaño and R Romero for Project LA 27, M. Vinocour for Project LA 29, I. Camilloni and V. Barros for Project LA 26. Expenses were covered by each Project.
The purpose of this meeting was: To share the information learned at the workshop Development and Application of Scenarios in Impacts, Adaptation and Vulnerability Assessments held in Norwich. To decide what socio-economic scenario(s) will be used by all four projects.
The group agreed only in the following points · To use SRES A2 as a common socio-economic scenario for all four projects in the region. Based on the SRES A2 socio-economic scenario, Mario Bidegain (LA26) and Inés Camilloni (LA32) will analyze the available IPCC climatic scenario outputs. Those models that best represent the actual regional climate (sea level pressure and precipitation) will be selected. To do so, it will be follow two steps. In the first step, model performance in reproducing the sea level pressure fields both in the mean annual value as well as in their annual cycle will be checked. During the second step the best models will be then checked in its monthly precipitation outputs against current data. To compare these results, the 1961-2000 climatology will be used as a baseline.
10 · The results from this activity will then be shared with the other participants, and a discussion session will be held in approximately 4 months.
Also, a common regional proposal to address vulnerability studies in the region now under preparation, was discussed
C) Description of Difficulties Encountered and Lessons Learned
TASK 5 The election of the urban case studies for this research project -Avellaneda Department and La Boca neighborhood, in the city of Buenos Aires– posed problems in the procurement of both socioeconomic and demographic statistical information.
One problem is related to the geographic scale and the existence of proper statistical information (above all regarding updated information). Two of the secondary sources that offer socioeconomic and demographic data are: A) National Census on Population and Housing (CNPyV), and B) Permanent Households Survey (EPH); both in charge of the National Institute for Statistics and Censuses (INDEC). Each of them shows particularities that will be briefly characterized in the following table.
CHARACTERISTICS OF THE INFORMATION SOURCES National Census on Population and Permanent Households Survey (EPH) Housing (CNPyV) Survey of the total population (census Sample on urban populations in cities of information). more than 5.000 inhabitants. That is to say the 73% of the urban national total and the 63% of the national total (sample information). Made each 10 years. Conducted each semester (generally in March and October). High degree of geographic separation It cannot be geographically separated. The (country, province, Municipality/ information is based on a city or Department, Census fraction/ School conglomerate. District and census zone). That is why it is It allows analysis of processes throughout the most frequently used by social time (e.g. poverty). programs, in spite of giving information for a given moment (picture type information). Measures poverty through the direct Measures poverty through the indirect method of the Unsatisfied Basic Needs method of the Poverty Limit (LP). index (NBI). Poverty measured through NBI is related Poverty measured through LP is related to to structural variables (housing, services, income variables. etc.). Surveys mainly what is known as Surveys mainly what is known as “the new
11 “structural poor”. poor”.
From this table we can conclude that the only statistical information source that can be used for the selected study cases is the CNPyV, since the information from the EPH is only valid for the whole of Buenos Aires city.
The second problem refers to the availability of updated socioeconomic and demographic information. Although the INDEC carried out the CNPyV in November 2001, there are no official final data to date. According to officials from this institution, this data might be available by the end of this year of beginning of 2003. However, it was possible to obtain the preliminary results of the CNPyV 2001 (in digital format), but without the accuracy margin.
TASK 10 The most important difficulty in this phase was the construction of topographic maps with detailed altimetric data since present contour line information has a 2.5-m equidistant resolution. This value is not enough to precisely define areas that could be affected by future marine ingressions, according to the IPCC (2001) predicted sea level rise.
To solve this problem, it is necessary to interpret micromorphological characteristics and their relation with the hydrodynamics of the interphase zone. The point is that marine transgression could be caused not only by sea-level rise promoting flooding and marine water advance through natural or artificial drainage, but also quick erosion with the consequent coastline retrocession and a backward rate depending on litological and geomorphologic characteristics of the area.
TASK 13 It was intended to test results from at least 7 to 8 SRES-A2 scenarios from different models for the region of the RP. However, there are only 4 of them, namely, the HADCM3 (Hadley Centre-UK), the CSIRO-Mk2 (CSIRO-Australia), the NCAR-PCM (NCAR-USA), and the CGCM2 (CCC-Canada) in the Modelle and Daten (MOD) page of IPCC. Until now, we have only succeeded to get another output, in this case from the LMD, but it was not exactly a SRES-A2 run.
TASK 20 There are not long-term discharge records for the Paraná and Uruguay rivers near their outlet on the RP. Long-term records, necessary for climatological analysis, are only available north of 26°S.Though, most of the discharge comes from the region north of this latitude, this lack of data adds uncertainty regarding the discharge of its main tributaries in the RP.
TASK 31 The only location for with long term records of waves are available is in the middle of the RP at its mouth. Evaluation of waves on the coast will require an additional effort through modeling.
D) Description of Tasks to be Performed in the Next Eight Month Period
Tasks numbers as in the working plan. It is indicated when the task was already initiated as reported in point B .In brackets the end date.
12 6 INITIATED. Initial presentation of the Project and its objectives, through interviews with stakeholders (September 2002) This activity was already prepared, but presentations in formal meetings will be made during the second semester.
8 INITIATED. Development of a large-scale version of the HIDROBID II model (August 2002) This activity is almost finished. It remains to end up the calibration process using forcing with extreme winds provided by task 7.
10 INITIATED. Photo interpretation of dry, normal and flood events (Scale 1: 20 000 and 1: 60 000) (November 2002) It requires further feedback from topographic measurements (Task12).
11. INITIATED. Data bases construction, in a GIS environment. Point 3 of the Joint Document. (October 2002) It will require more expert work.
12. Topographic measurements and fieldwork will be carried out to produce detailed altitude level maps of coastal areas subject to possible floods (November 2002)
13. INITIATED. Election of future climate scenarios in cooperation with Project L32 (September 2002) Remains to calculate objective indexes for comparison between models and actual climate. Make the final choice of models and produce the ensemble scenarios
14. Training in the hydro-dynamical model HamSOM (August 2002)
15 INITIATED. Study of weather storms over the region embracing the RP using NCAR/NCEP reanalysis for the period 1950-2000. Study of frequency and strength of these systems and of its seasonal and interannual variability, its trends or decadal variability (August 2002) Further elaboration required.
16 Development of future scenarios for the Paraná delta growth. J. Codignotto (December 2002)
17 Joint Course on Climate Change with Project L32 as explained in Point 11 of the joint document (September 2002) A five-day course will be lectured in Montevideo by Drs. V. Barros and S. Bischoff.
18 Joint workshop with Project L32 as explained in point 10 of the joint document. Coordination with Project L32 (September 2002)
13 This workshop is going to be held in Montevideo. It will include general presentations from both Projects and individual presentations as well discussions on common subjects. The participants of our Project will be V. Barros, S. Bischoff, A. Menendez, C. Natenzon, J. Codignotto, R. Kokot, I. Camilloni and W. Vargas. Other participants might be funded by collateral funds
19 Writing of a paper manuscript on the study of weather storms over the region embracing the Rio de la Plata using NCAR/NCEP reanalysis for the period 1950-2000 (October 2002)
20 INITIATED. Estimate of extreme streamflow events. Statistical approach based on historical data and a conceptual approach based on the relationship of rainfall and discharge with SST in the sub-basins of the Paraná and Uruguay rivers. Point 1 of the Joint Document (November 2002) It is being made. It is now required the future precipitation scenarios to estimate the future discharges.
21 Writing of a paper manuscript on extreme streamflow events in the Paraná and Uruguay rivers (December 2002)
22 Consultation about demands and communication of Project partial results with stakeholders through mail and email (December 2002)
23 Implementation of the hydrodynamic models (November 2002)
24 Geomorphology description and study of the evolution of the coastal area and construction of geomorphology maps (February 2003)
25 Develop of a Social Vulnerability Index to flooding in a GIS environment. Point 3 of the Joint Document (February 2003)
26. Preparation and submission to AIACC of the end of year 2002 progress report and financial report (January 2003)
27. Selection of sea level scenarios according to TAR IPCC (January 2003)
28. Validation of the ETA model and the hydrodynamic models (February 2003)
29. Running of the ETA and the hydrodynamic models for the dates of the oceanographic campaigns conducted by Project L32 as explained in point 7 of the joint document (March 2003)
30. INITIATED. Selection of some cases of typical weather storms and analysis of them with the ETA model to estimate the surface wind fields (December 2002) Remain the detailed study of the cases and their evolution.
14 31. INITIATED. Development of strong waves scenarios (October 2002) It is necessary to estimate waves at the coast of the RP. It is being made by modeling.
E) Anticipated Difficulties in the Next Eight-Month Period
Tasks numbered as in the working plan 10. Photo interpretation of dry, normal and flood events (Scale 1: 20 000 and 1: 60 000) The objective of this activity is to produce topography with a resolution of at least 20 cm. in the coastal area of the Samborombón bay. At the moment, there are some doubts on the full achievement of this task.
14. Training in the hydro-dynamical model HamSOM There is no certainty that this model can be handed to the personnel of the Project. In such a case, other similar alternative models will be explored
F) Attached Draft Documents
Ten annexes with more detailed information about the tasks reported in point B of the document are attached. In addition, three presentations at the Norwich and Trieste workshops are included.
15 AIACC REGIONAL STUDY EXPENSE REPORT Project statement of allocation (budget), expenditure and balance (expressed in US$) covering the period: 01 JANUARY 2002 – 30 JUNE 2002
Project Number: AIACC_LA26
Principal Investigator(s): VICENTE BARROS
Project Title: “THE IMPACT OF GLOBAL CHANGE ON THE COASTAL AREAS OF THE RIO DE LA PLATA: SEA LEVEL RISE AND METEOROLOGICAL EFFECTS
Supporting Organizations: Global System for Analysis, Research and Training (START), Third World Academy of Sciences (TWAS) United Nations Environment Programme (UNEP
I hereby certify that all information contained in this expense report is true and correct.
Signed: ______Date: Buenos Aires, 30 de Junio de 2002
Signed: ______Date: Buenos Aires, 30 de Junio de 2002 CASH ADVANCE INFORMATION AND REQUEST: (All figures should be in US Dollars)
A. Amount of Previous Cash Advances: Date: 04/12/02 Amount: 11000 u$s
Date: 05/14/02 Amount: 12620 u$s
TOTAL(1): 23620 u$s
B. Expenditures (by Reporting Period)
Total Expenditures for Period 01 Jan 2002 – 30 Jun 2002: 11400.47 u$s
Total Expenditures for Period 01 Jul 2002 – 31 Dec 2002: 0
Total Expenditures for Period 01 Jan 2003 – 30 Jun 2003: 0
Total Expenditures for Period 01 Jul 2003 – 31 Dec 2003: 0
Total Expenditures for Period 01 Jan 2004 – 30 Jun 2004: 0
Total Expenditures for Period 01 Jul 2004 – 31 Dec 2004: 0
TOTAL(2): 11400.47 u$s
C. Total Cash-In-Hand: =TOTAL(1) minus TOTAL(2): 12219.53 u$s
D. Total Estimated Expenses for Subsequent 8-Month Period: 42253.14 u$s (from expense form)
E. Total Cash Advance Requested (D. minus C.): 30033.61 u$s Object of Expenditure Project Current Period Cumulative Estimated Budget Expenses Expenses for Expenses for Allocation for 2002 Subsequent 8- Year Month Period
(USD) (USD) (USD) (USD)
PERSONNEL 24250 u$s 4,187.26 4,187.26 24,758.00 Claudia Herrera 3,600.00 300.35 300.35 1,943.00 Julieta Berrenechea 1,800.00 388.70 388.70 1,571.00 Diego Ríos 2,250.00 353.35 353.35 1,143.00 Mariano Re 3,600.00 600.70 600.70 2,186.00 Gustavo Escobar 6,000.00 1,943.46 1,943.46 1,886.00 Silvia Romero 1,600.00 600.70 600.70 486.00 Moira Doyle 3,000.00 0.00 0.00 2,200.00 Elvira Gentile 2,400.00 0.00 0.00 1,943.00 Vicente Barros 500.00 0.00 0.00 2,400.00 Susana Bischoff 500.00 0.00 0.00 1,200.00 Angel Menendez 0.00 0.00 0.00 1,800.00 Claudia Natenzon 0.00 0.00 0.00 1,800.00 Jorge Codignotto 0.00 0.00 0.00 1,800.00 Roberto Kokot 0.00 0.00 0.00 1,200.00 Inés Camilloni 0.00 0.00 0.00 1,200.00
MATERIALS AND 500 u$s 318.59 318.59 1,700.00 SUPPLIES
EQUIPMENT[2] 1500 u$s 0.00 0.00 2,200.00
TRAVEL[3] 7100 u$s 599.48 599.48 7,440.00 Vicente Barros (coordination) 453.42 453.42 300.00 Mario Caffera (coordination) 146.06 146.06 240.00 Jorge Codignotto (Fiel-Work) 0.00 0.00 900.00 Claudia Herrera (Field-work) 0.00 0.00 900.00 Roberto Kokot (Field -woork) 0.00 0.00 900.00 Vicente Barros (Workshop) 0.00 0.00 400.00 Susana Bischoff (Workshop) 0.00 0.00 400.00 Angel Menendez (Workshop) 0.00 0.00 400.00 Claudia Natenzon (Workshop) 0.00 0.00 400.00 Jorge Codignotto (Workshop) 0.00 0.00 400.00 Roberto Kokot (Workshop) 0.00 0.00 400.00 Inés Camilloni (Workshop) 0.00 0.00 400.00 Walter Vargas (Workshop) 0.00 0.00 400.00 Vicente Barros (Course) 0.00 0.00 500.00 Susana Bischoff (Course) 0.00 0.00 500.00
CONSULTANTS[4] 10,000.00 5,300.34 5,300.34 2,500.00 D'Onofrio Enrique 3,000.00 2,650.17 2,650.17 Oscar Andres Frumento 3,000.00 2,650.17 2,650.17 Claudia Simionatto 1,500.00 0.00 0.00 1,250.00 Mario Nuñez 1,500.00 0.00 0.00 1,250.00
TELECOMMUNICATIONS 1,000.00 0.00 0.00 500.00
COMPUTER SERVICES 1,000.00 0.00 0.00 1,000.00
PUBLICATION COSTS 0.00 0.00 0.00 1,000.00 (INCL. DISSEMINATION)
OTHER[6] 0.00 0.00 0.00 0.00
INDIRECT COSTS 1,890.00 994.80 994.80 1,155.14 TOTAL 47,240.00 11,400.47 11,400.47 42,253.14
1 u$s = 2.83 $ (Banco Nación Argentina, date: 04/12/02) ANNEX B1 (M. Re and A. Menendez) SYSTEM SENSITIVITY TO CHANGES IN THE FORCINGS Sensitivity studies were undertaken with the RIO DE LA PLATA 2000 model in order to quantify changes in the hydrodynamic response of the Río de la Plata to variations in the forcings. In particular, test to variations in the tributary discharges and in the wind intensity were performed.
1 Changes in the tributary discharges Keeping the same tidal wave as for run B0, the discharges were varied according to the following:
Run B1: discharges were doubled relative to B0 (representative of relatively high discharges) Run B2: discharges were reduced to one half relative to B0 (representative of relatively low discharges) Run B3: discharges were reduced to one tenth relative to B0 (representative of very low discharges) Run M1: discharges were taken as the peak values attained during the 1983 flood (representative of very high discharges) Run M2: discharges were increased 50% relative to M1 (representative of extremely high discharges)
In the following table the discharge values for each run corresponding to each tributary are presented. Discharge of tributaries for each run (m3/s) B0 B1 B2 B3 M1 M2 Paraná Guazú 13500 27000 6750 1350 38000 59400 Paraná de las Palmas 5200 10400 2600 520 15400 23100 Uruguay 4500 9000 2250 450 30000 45000
The differences between the instantaneous water level for each run and the one corresponding to the base run B0 were taken as a measure of the system change. Figures 1 presents these differences for Buenos Aires..
Figure1 Water level differences at Buenos Aires station due to discharge variations
0.15
0.13
0.10
0.08
0.05
0.03
0.00
water level differences (m) -0.03
-0.05 0.00 24.00 48.00 72.00 96.00 120.00
time (hr) B3 B2 B1 M1 M2
1 The following table presents the mean value of the differences for each run, corresponding to each station.
Mean water level differences for each run (m)
B1 B2 B3 M1 M2 San Fernando 0.15 -0.08 -0.15 0.42 0.72 Martín García 0.24 -0.13 -0.24 0.59 1.04 Buenos Aires 0.11 -0.06 -0.11 0.29 0.51 Colonia 0.13 -0.07 -0.12 0.31 0.54 La Plata 0.07 -0.04 -0.07 0.18 0.32 Montevideo 0.02 -0.01 -0.02 0.05 0.09
2 Changes in the winds Situations with different but uniform wind intensities and directions were considered. The wind duration was always taken as 24 hours, acting from the initial instant -larger than the adaptation time of the system, which is of the order of 16 hours- in order to attain the limiting stage. Four directions were taken as the most frequent ones: E, NE, SW and SE. They were combined with four wind intensities, covering the most frequent range: 10, 30, 60 and 80 km/h.
Figures 2 shows the resulting set up or set down for Buenos Aires station for the 30 and 60 km/h winds.
0.60
0.50
0.40
0.30
0.20
0.10
0.00 water level differences (m) -0.10
-0.20 0.00 10.00 20.00 30.00 40.00 50.00 60.00 time (hr) E NE SW SE
(a) 30 km/h
Figure 2 Water level differences at Buenos Aires station due to wind action
2
In the following table the obtained water level differences are summarized.
Water level differences for each run (m) E NE SW SE San 0.02 0.01 -0.01 0.03 Fernando Martin 0.02 0.00 0.00 0.03 Garcia 10 km/h Montevideo 0.00 -0.01 0.01 0.01 Buenos Aires 0.02 0.01 -0.01 0.02 La Plata 0.01 0.00 0.00 0.02 Colonia 0.01 0.00 0.00 0.02 San Fernando 0.34 0.10 -0.10 0.39 Martin 0.26 -0.03 0.03 0.40 Garcia 30 km/h Montevideo -0.03 -0.12 0.12 0.07 Buenos Aires 0.29 0.08 -0.08 0.34 La Plata 0.21 0.04 -0.03 0.26 Colonia 0.20 -0.02 0.02 0.30 San Fernando 1.64 0.47 -0.68 1.90 Martín 1.28 -0.18 0.10 1.89 Garcia 60 km/h Montevideo -0.16 -0.57 0.57 0.38 Buenos Aires 1.45 0.40 -0.46 1.68 La Plata 1.09 0.24 -0.17 1.35 Colonia 1.02 -0.09 0.09 1.50 San Fernando 2.93 0.87 -0.10 3.41 Martín 2.34 -0.37 0.03 3.38 Garcia 80 km/h Montevideo -0.27 -1.06 0.12 0.71 Buenos Aires 2.63 0.76 -0.08 3.07 La Plata 2.04 0.50 -0.03 2.54 Colonia 1.87 -0.18 0.02 2.74
References [1] Jaime, P., Menéndez, A.N., 1999, Modelo hidrodinámico Río de la Plata 2000, Report LHA-INA 183-01- 99. September. [2] Menéndez, A. N., 1990, Sistema HIDROBID II para simular corrientes en cuencos, Revista internacional de métodos numéricos para cálculo y diseño en ingeniería, Vol. 6, 1.
3 ANNEX B2 (G. Escobar and V. Barros)
SURFACE WIND FROM NCEP/NCAR REANALYSIS. CLIMATOLOGICAL FIELDS Seasonal mean fields of the winds and geopotential at 1000 hPa These field were calculated using NCEP/NCAR reanalysis for the 1950/2000 period, The region of analysis was 25°S-45° S and 67.5°W-45°W .The seasons were defined as summer (DJF), autumn (MAM), winter (JJA) and Spring (SON).
The circulation over the RP is under the influence of the southwester border of the South Atlantic high (SAH). This circulation shift southward from winter to summer and northward from summer to winter. This implies a stronger westward component in summer than in winter (Fig 1). As a consequence the mean high of the water levels in summer should be greater in summer than in winter in the Argentine coast of the RP estuarine This was confirmed by the analysis made under task 3
.
4
5
Fig. 1
Interdecadal variability of the mean seasonal geopotential and wind fields Mean fields for the 1951/1960, 1961/1970, 1971/1980, 1981/1990 y 1991/2000 decades for each of the four seasons indicate a general shift southward in the circulation associated to the southwester border of the SAH. (Only summer fields are shown in Fig. 2) It was more evident in summer, important in the transition seasons and almost null in winter, as a result the westward component of the wind over the RP and possible its water level. This is consistent with results found under task 3.
6
Fig. 2: (summer)
The differences between the mean fields of geopotential and wind in 1000 hPa of the 60/70, 70/80, 80/90 and 90/00 decades with respect to the 50/60 decade make more evident the shift to the south of the western part of the SAH (Fig. 3, only summer is shown).
7
Figure 3
A principal component analysis (PCA) performed on the seasonal geopotential field confirms the southward shift of the mean seasonal circulation. The first PC explains 40 % of the variance and it is associated more to the winter circulation The second PC, explaining almost the same variance (39.8 %) has a pattern that resembles more the summer circulation. The third PC explains considerably less variance (11.7), but it is associated to cyclogenesis and intense westward winds over the RP and consequently favors the floods over the Argentine coast of the RP (Fig.4)
8 1° CPs - 40,0 % INVIERNO 1955
-26 -26
-28 -28
-30 -30
-32 -32
-34 -34
-36 -36
-38 -38
-40 -40
-42 -42
-44 -44
-66 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46 -66 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46
2° CPs - 39,8 % VERANO 1990
-26 -26
-28 -28
-30 -30
-32 -32
-34 -34
-36 -36
-38 -38
-40 -40
-42 -42
-44 -44
-66 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46 -66 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46
3° CPs - 11,7 % PRIMAVERA 1989
-26 -26
-28 -28
-30 -30
-32 -32
-34 -34
-36 -36
-38 -38
-40 -40
-42 -42
-44 -44
-66 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46 -66 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46
Fig. 4: Principal components (left) and observed fields highly correlated (right)
9
There was a significant increment of the variance explained by the second mode, more associated to the summer circulation and the westward component of the wind over the RP from the 1950/60 decade to the 1990/00 one. At the same time there was a significant reduction of the first mode, more associated to the winter circulation in the same period. The third mode potentially associated to floods in the Argentine coast also increased during this period
10 ANNEX B3
Report on the Tide Dynamics of the Rio de la Plata and Training course By Enrique E. D’Onofrio and Mónica E. Fiore Activity developed in the Departamento de Ciencias de la Atmósfera y los Océanos Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires May 2002
1.INTRODUCTION This work is not exclusively aimed at presenting basic knowledge on tides but also at meeting several technical needs required by the multidisciplinary working group. Item 2 reviews .the characteristics of tides in the Atlantic coast of Argentina and Uruguay.
The mean water level trend in the Port of Buenos Aires is estimated in Item 3, using a series of data from the period 1905 – 2001. In Item 4, the same data series is used to perform a seasonal statistical analysis to determine the corresponding trends.
The greatest storm surges in the Port of Buenos Aires for the period 1950 – 2000 are calculated in Item 5. In addition, annual and seasonal occurrence frequency of positive storm surges is statistically analyzed.
Finally, in Item 6, we estimated tide levels to be used in the geological study.
2.CHARACTERISTICS OF TIDES IN THE ATLANTIC COAST OF ARGENTINA Because of the shape and distribution of the depth contours that run parallel to the coastline, the Argentine Sea is a vast tray open to the great surrounding ocean basins, in which lunisolar tidal waves that propagate from SE to NW into it are generated (Balay, 1961).
These waves refract on the continental slope, undergoing from there on all kind of transformations, due to the progressive water shallowing and to meteorological action, that together with Earth rotation effects on moving water masses, sometimes cause oscillation amplitudes to grow until they reach outstanding levels near the coast (12m amplitude in the Province of Santa Cruz).
Because of these facts, tides in our coasts have very different forms and amplitudes. A way of classifying tides is the application of the method suggested by Courtier (Defant, 1961). This method characterizes four main forms of the tide, based on the result from dividing the sum of the amplitudes of diurnal waves K1 and O1 by the sum of the semidiurnal M2 and S2, the major constituents in each group. The result (F) will be a number smaller than 1 if semidiurnal constituents predominate and greater than one with the diurnal constituents predominating.
K + O F = 1 1 M 2 + S2
If F < 0.25; the tide has the semidiurnal form. There are two low tides and two high tides per day, with almost equal heights. In addition, the intervals between the passage of the moon across the meridian and the occurrence of the high tide are approximately constant for a given place. In our country this form is observed from Bahía Blanca to Tierra del Fuego, at the mouth of Le Maire Strait. 10
If 0.25 £ F < 1.5; the tide is mixed predominately semidiurnal. In most of the cases there are only two high tides and two low tides per day, with strong diurnal inequalities, although occasionally there can be only one high tide and one low tide per day. The latter takes place at maximum moon declination. In our country this form can be observed in the Río de la Plata, the Atlantic coast of the Province of Buenos Aires up to Quequén, the Beagle Channel and the Argentine Antarctic Sector.
If 1.5 £ F < 3; tide is mixed predominately diurnal. There are both one high tide and one low tide per day (when moon declination is almost zero), and two high tides and two low tides with strong diurnal inequality (when the moon is at maximum declination). If F ³ 3; tide is diurnal, with one high and one low tide per day. The two latter forms are not present in our coasts.
Figures 1 and 2 (Simionato et al., 2002) correspond to different resolution nested model outcomes. These figures show the dynamics of tides in the Argentine Sea, from cotidals and isoamplitudes of the main lunar semidiurnal wave -M2- which in our coast represents more than 65% of tide energy.
Isoamplitude (meters) and cotidal (degrees) Charts for the M2 constituent Figure 1
From cotidal analysis it appears that propagation of tides along the coastline up to San Clemente del Tuyú takes approximately 26hs, while it takes about 12 hours to travel along the Río de la Plata because the mean depth in the area is about 5m. Two amphydromic points are observed, one at approximately 41° S (Figure 2) and the other one at 47° S (Figure 1). From the isoamplitude charts it can be seen that the amplitude of M2 varies from about 4m in the province of Santa Cruz to less than 0.30m in the inner Río de la Plata.
11
Isoamplitude (meters) and cotidal (degrees) Charts for the M2 constituent Figure 2
3. MEAN WATER LEVEL TREND IN THE PORT OF BUENOS AIRES In the last decades, an increase in mean sea level has been observed in different parts of the planet, the most obvious consequences of which are coastal erosion and floods over low lands. Because of this, it is of major importance to know the decadal changes in mean level in order to plan coastal development and design defenses for flood prevention.
In the Southern Hemisphere, where observations are limited, Barnett (1982), Lanfredi et al. (1988), calculated the mean level trends for the ports of Montevideo, Uruguay and Quequén, Argentina, respectively. Later, Lanfredi et al., (1998) determined mean level trends in the Ports of Buenos Aires, Mar del Plata and Puerto Madryn (Argentina).
In the present work we extend the observation series used by Lanfredi et al., (1998) and we recalculate mean water level trend in Buenos Aires.
3.1 Data series For the Port of Buenos Aires hourly data recorded over the period 1905-2001 are available. From 1905 to 1959, observations were performed by the Ministry of Public Works and Services (Ministerio de Obras y Servicios Públicos -MOSP) using a float mareograph (Basic Tide Gauges, UNESCO, 1985). From 1959 to 2001 the Navy Hydrographic Service (Servicio de Hidrografía Naval -SHN) performed measurements using a similar mareograph at a station close to the former. Distance between both stations is 9km along which coastal topography and morphology are uniform. On the other hand, both series have equal characteristics, and therefore they may be unified (D’Onofrio et al., 1999). The levels registered at both stations were referred to a common datum, Cero del Riachuelo. Annual mean water levels were calculated as the arithmetic average of hourly tide levels.
3.2 Analysis methodology There are periodic contributions –between 8 and 19 years- to the spectrum of annual mean water levels that might mask the trend we are to analyze (Godin, 1972). To attenuate these contributions a low pass filter was used. This filter was designed starting from the Kaiser – Bessel window 12
(Hamming, 1977) and following Harris’s (1978) indications, who highlighted the advantages of this window after performing a comparative analysis over a set of 22 windows.
Kaiser suggested the use of weights for the Fourier coefficients of the ideal filter, to attenuate the Gibbs phenomenon. Their mathematical expression is (Harris, 1978):
æ 2 ö I × a × 1- k 0 ç ( N) ÷ è ø wk k £ N I 0 (a ) 0 k > N
where 2 é n ù ¥ (x ) I (x) =1+ ê 2 ú 0 å ê ú n=1 n! ëê ûú is a modified Bessel function of the first kind of order zero. Kaiser weights are symmetrical with regard to k = 0 (wk = w-k) and have two parameters N and a . N is half the width of the window with (2 N +1) coefficients and it is related to the slope of the window. On the other hand, a controls the height and “ripples” of the window.
Parameters N and a can be calculated using the empiric formulae developed by Kaiser (Hamming, 1977):
0.1102×(A - 8.7) A >50 0.4 a 0.5842×(A - 21) + 0.07886×(A - 21) 21 < A £ 50
0 A £ 21 where A is the attenuation expressed in decibels, expressed by:
A = -20 . log10 d d being the size of the maximum ripple, and
A - 7.95 N = 28.72× DF where DF is the width of the transition area.
For this work, a non-recursive symmetrical low pass filter was designed with 17 elements and cut frequency 0.076 1/year. Figure 3 shows the filter weights and Figure 4 its transference function. As the number of elements had to be small according to the length of the series to be filtered, the transition zone of the filter caused unnecessary attenuation of some contributions and insufficient attenuation of others. To correct this the Fast Fourier Transform (FFT) was applied on the filtered series, to recolor it in the frequency domain, taking into account the filter transfer function. Finally we obtained the anti-transformation of the recolored function.
13
Results were adjusted to a straight line by means of the least square method, the slope of which corresponds to the value of the trend we need to estimate.
0.11
0.10
0.09
0.08
0.07
0.06
W(k) 0.05
0.04
0.03
0.02
0.01
0.00 1 3 5 7 9 11 13 15 17 k
Weights assigned to the filter applied to the series of the annual mean water levels Figure 3
1.0
0.8
0.6
0.4 H ( f )
0.2
0.0
-0.2 0.00 0.10 0.20 0.30 0.40 0.50 Frecuencia (1/año)
Frequency response of the filter applied to the series of annual mean levels Figure 4
3.3 Results Figure 5 shows the series of annual mean levels, the filtered signal and the calculated linear regression for the period 1905 – 2001. The trend obtained for the Port of Buenos Aires was 1.7 ± 0.1 mm/year with a correlation coefficient of 0,96. Lanfredi et al. (1998) obtained for the period 1905 – 1992 a mean water level trend of 1.6 ± 0.1 mm/year, results of both works are concurrent.
14
1050
1000
950
900
850
800
750 Nivel del agua (mm)
700
650
600 1900 1920 1940 1960 1980 2000 2020 Tiempo (años)
Nivel medio anual Nivel medio filtrado Recta de regresión
Annual mean water levels, filtered series and linear regression calculated over the latter Figure 5
4. STATISTICAL ANALYSIS OF MEAN WATER LEVEL IN THE PORT OF BUENOS AIRES It is performed a statistical analysis of the mean river level in the Port of Buenos Aires grouping the information into decades and seasons, starting from 1950.
4.1 Data series and methodology Using the same series of water levels that we described in Item 2.1, we estimated the mean levels for the trimesters December - January - February, March - April - May, June - July – August and September - October - November, in groups of 10 years. After that, the trends for each of the resulting series were estimated.
4.2 Results Figure 6 shows the mean water levels corresponding to the trimesters, per decade, as mentioned in 3.1. The same figure displays the adjusted straight lines by means of least squares for each series, equations and determination coefficients. Obtained slopes are in mm/10 years.
It can be seen that the highest mean levels correspond to the trimester December - January - February, while the trimester June – July – August has the lowest mean water levels. These results agree with those obtained by D’Onofrio et al., 1982.
These differences in water level are mainly due to meteorological contributions, long-term tide constituents such as Sa (solar annual) and Ssa (solar semiannual) and variations in water density. 15
Although values for all the obtained trends are similar to that calculated for the mean water level in the Port of Buenos Aires (Item 4.3), the trend corresponding to the trimester September - October - November has a slightly greater slope.
1000
950 y = 15.85x + 800.19 R2 = 0.918 900 y = 15.8x + 779.44 R2 = 0.8601 850
y = 19.567x + 713.61 800 R2 = 0.8219
Altura (mm) 750
700 y = 15.7x + 660.06 R2 = 0.6051 650
600
1912 / 21 1922 / 31 1932 / 41 1942 / 51 1952 / 61 1962 / 71 1972 / 81 1982 / 91 1992 / 01 Dic-En-Feb Mar-Abr-May Jun-Jul-Ago Sep-Oct-Nov
Seasonal mean water levels per decade and corresponding linear regressions Figure 6
5. DETERMINATION OF THE GREATEST STORM SURGES IN THE PORT OF BUENOS AIRES IN THE PERIOD 1950 - 2000 Combination of high astronomical tides and major storm surges are the cause for floods in coastal areas. Some low areas of the city of Buenos Aires and its surroundings are affected by such events.
The first flood in this area that has been reliably recorded took place on 5th and 6th June 1805. On that occasion strong southeast winds caused a river level rise that seriously affected the coastal area, and caused several ships to sink in the Port of Buenos Aires. During the XIX century many different intensity southeaster winds continued to produce considerable damage and even killed people. Unfortunately for any of these cases there are no water level records available, comparable to those recorded in the XX century, as systematic measurements of river levels referred to land benchmarks had not been initiated yet.
Here, we will determine the maximum level and duration of positive storm surges. To achieve this, we have set the minimum level and duration to be exceeded by the storm surges we want to select.
5. 1 Data series We used hourly water level records from 1950 to 2000 with some information gaps (Table 1). Measurements were carried out by the Ministry of Public Works and Services (MOSP) at the mouth of the Riachuelo and by the Navy Hydrographic Service (SHN) at the Palermo
16 mareographic station. The latter is placed at the head of the Fishermen Club pier in front of Aeroparque Jorge Newbery.
Station MOSP SHN SHN Registry 1950-1961 1962 1965-2000 Table 1
In order to unify the records obtained at both stations the following was considered: · In both cases, observations were performed using float mareographs (Basic Tide Gauge, UNESCO, 1985), with an accuracy of ±1cm. · Records from both stations are referred to the same Tide Datum (Cero del Riachuelo). · Distance between both stations is approximately 9km, along which coastal topography and morphology are uniform. · There are no significative differences between amplitudes and phases of the harmonic constituents of both places, nor there are in simultaneously recorded storm surges (D’Onofrio et al., 1999).
5.2 Analysis methodology Storm surges were obtained from the difference between observed hourly levels and their corresponding predicted levels. Considering the length of the records and the possible modifications of astronomical tide, harmonic analyses were performed for periods of 19 years, by means of the least square method (Foreman, 1977,1978). Estimated harmonic constants were used for annual tide predictions for each period. This allowed minimizing possible trends due to tide amplitude variations caused by changes in the morphology of the area between 1950 and 2000.
In order to evaluate the quality of the obtained remainders, yearly spectral analyses were performed. From the spectra analysis, it appears that the energy present in the semidiurnal and diurnal tide bands is two orders of magnitude lower than the energy of the astronomical tide, what guarantees that storm surges were correctly separated from observed levels.
Figure 7 shows one of the power spectra for the obtained remainders, and superimposed, the discrete spectrum of constituents M2 and O1. The energy present in the semidiurnal and diurnal tide bands is two orders of magnitude lower than the energy of the astronomical tide.
17
0.010 0.1
M2 0.008 Espectro de los residuos 0.08
Espectro discreto de la componente 0.006 0.06
0.004 0.04
O1 Espectro de potencia (m²)
Espectro de potencia (m²) 0.002 0.02
0.000 0 0.03 0.04 0.05 0.06 0.07 0.08 0.09 Frecuencia (1/h)
Power spectrum of the remainders for year 1991. Superimposed is the discrete spectrum of constituents M2 and O1. Figure 7
To select the greatest positive storm surges we decided to take into account the events that have a duration greater than 6 hours, with levels equal or greater than 0.30m for all the cases and with maximum level equal or greater than 1.60m. The magnitude of this level guarantees that the observed phenomenon is basically caused by wind action, allowing selection of the major events within each year.
5.2 Results An excel file ( ODT6160.XLS ), attached to this work, contains the obtained results. The heading of this file reminds the conditions adopted for event selection. The first four columns contain information on the year, month, day and hour of occurrence of the maximum event remainder. Observed water levels and estimated storm surges are in columns 5 and 6 respectively. Column 7 presents the event duration in hours.
Annual and seasonal occurrence frequencies of positive storm surges were analyzed. With the complete set of positive storm surges a histogram of annual frequency was created (Figure 8). This histogram shows a trend of 0.07 ± 0.01 events/year. The greatest number of events (17) took place in 1993 and the smallest (2) was observed in 1956. The mean frequency of positive storm surge occurrence for the studied period yields 7.75 events/year.
Figure 9 is a monthly frequency histogram. Each class interval contains all the events of a single month of all the analyzed years. We can see that the number of events decreases from February (maximum) to July, and then it grows up to October.
18
18
16
14
12
10
8 Eventos
6
4
2
0
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 Años
Annual frequency histogram for positive storm surges Figure 8
50
45
40
35
30
25 Eventos 20
15
10
5
0
Abril Julio Enero Marzo Mayo Junio Febrero Agosto Octubre Diciembre Septiembre Noviembre
monthly frequency histogram for positive storm surges Figure 9
6. TIDE DATA FOR SOME AREAS OF SAMBOROMBON BAY Within the framework of this project, for geological purposes, water levels observed at the following stations and dates are needed: l Mouth of the Río Salado on 12/02/1964 at 10:36hs. 19 l Punta Piedras on 12/02/1964 at 10:28hs and on 06/06/1991 at 13:46hs. l Coastline of Samborombón Bay at the latitude of General Lavalle on 12/02/1964 at 11:26hs.
Given that there were no tide records available for the requested dates, we decided to perform harmonic tide predictions. In order to determine harmonic constants for each locality, we used a zonal tide-predicting model for the Río de la Plata (Legal, 1995).
As tide observations from Torre Oyarvide (Latitude: 35° 06’ S, Longitude: 57° 08’ W) were available for June 1991, we made a tide prediction that subtracted from the observations allowed for estimating storm surge. The closeness of Torre Oyarvide to Punta Piedras allows assuming an equal storm surge having place in both sites. Then, this number was added to the tide predicted at Punta Piedras to obtain the recorded level.
The obtained results are displayed in Table 2.
Site Date Predicted level Observed level Mean level Río Salado 12/02/1964 at 10:36hs 127 cm ------91 cm Punta Piedras 12/02/1964 at 10:28hs 105 cm ------85 cm Punta Piedras 06/06/1991 at 13:46hs 68 cm 177.5 cm 85 cm General Lavalle 12/02/1964 at 11:26hs 136 cm ------91 cm Table 2
The mean levels in Table 2 are referred to the sounding reduction levels in the area, that are the same as the tide measurement data. Times correspond to time zone +3 west of Greenwich.
REFERENCES BALAY M.A., 1961. El Río de la Plata entre la Atmósfera y el Mar, Publ.H-601, Servicio de Hidrografía Naval, Armada Argentina. 166 páginas.
BARNETT T.P., 1982. On possible change in global sea level and their potencial cause. SIO Reference Series, 82 - 10, 34pp.
BARTH M.C. TITUS J.G., 1984. Greenhouse effects and sea level rise. A challenge for this generation. New York, Van Nostrand Rienhold Co., 325pp.
DEFANT A., 1961. Physical Oceanography. Volume II. Pergamon Press. 598pp.
D’ONOFRIO E.E., FIORE .M.E., ROMERO S.I., 1999. Return periods of extreme water levels estimated for some vulnerable areas of Buenos Aires. Continental Shelf Research. 19 (1999) 1681 -1693.
FOREMANN M. G. M., 1977. Manual for tidal heights analysis and prediction. Pac. Mar. Sci. Rep. 77 – 10, 97 pp.
FOREMANN M. G. M., 1978. Manual for tidal heights analysis and prediction. Pac. Mar. Sci. Rep. 78 – 6, 70 pp.
GODIN G., 1972. The analisys of tides.Liverpool University Press, 264pp. 20
HAMMING R.A., 1977. Digital filters. Prentice - Hall, 223pp.
HARRIS F., 1978. On the use of windows for harmonic analysis with discrete Fourier transform. Proceedings of the IEEE, 66-1, 51, 83pp.
KANTHA L.H., 1995. Barotropic tides in the global oceans from a nonlinear tidal model assimilating altimetric tides. 1. Model description and results. Journal of Geophysical Research, 100 (C12): 25283-25308.
LANFREDI N. W., D'ONOFRIO E. E., MAZIO C:A:, 1988. Variations of the mean sea level in the southwest Atlantic Ocean. Continental Shelf Research, 8(11), 1211 -1220.
LANFREDI N. W., POUSA J.L., D'ONOFRIO E. E., 1998, Sea-Level Rise and Related Potential Hazards on the Argentine Coast. Journal of Coastal Research. Vol 14. No. 1, pp. 47-60.
LEGAL N., 1995. Desarrollo de un modelo zonal de predicción de marea, utilizando cartas de cotidales e isoamplitudes. Beca de perfeccionamiento CONICET.
LE PROVOST, C., LYARD, F., MOLINES, J.M.,GENCO, M.L. and RABILLOND, F. (1998). A hydrodynamic ocean tide model improved by assimilating a satellite altimeter-derived data set. Journal of Geophysical Research, 103 (C3): 5513-5529.
PUGH D.T., 1987 Tides, Surges and Mean Sea - Level. N. John Wiley & Sons. 472pp.
SIMIONATO C.G., DRAGANI W., NUÑEZ M., ENGEL M., 2002. A set of 3-d nested models for tidal propagation from the Argentinean Continental Shelf to the Río de la Plata Estuary. Enviado a Continental Shelf Research.
UNESCO, 1985. Manual on sea-level measurement and interpretation. IOC Manual and Guides Nro.14, 83pp.
WARRICK R.A. (1992). Climate and Sea Level Change: Observations, Proyections and Implications (IOVERVIEW). Warrick, R.A., Barrow, E.M. and Wigley, T.M.L. Cambridge University Press.
21
ANNEX B4 (J. Barrenechea and C. Natenzón)
Name Description Relevant features and background SIFEM Sistema Federal de Governmental Its main goal is to coordinate prevention, Emergencias- Secretaría de Institution response and re-construction actions among Seguridad Interior, Presidencia de National level national institutions involved in different la Nación (Federal Emergency risk scenarios. Through SIFEM it is System, Secretariat of Internal possible to obtain information about the Security, executive office of the whole governmental institutional system President) and on different stages of the risk management.. Defensoría del Pueblo Adjunta de Governmental Focuses its activity on communal problems, la Ciudad de Buenos Aires. Area Institution emphasizing claims and solutions with Medioambiente, Urbanismo y Provincial level participatory and pluralist methods. It has Comunicación. been involved in the subject of catastrophic Office of the Deputy Ombudsman urban floods. It collaborates with the City of the Buenos Aires City. Legislature giving advice on environmental Environment, Urban Planning and and urban issues. It keeps in touch with Communication Area NGO’s, neighbors, journalists, governmental officers and legislators. Fundación Ciudad (Foundation for Non-governmental It has expertise in urban problems, the City) organization related to especially water use and management. Main Buenos Aires and the goal: nexus between affected people and AMBA policy makers. Noteworthy production of working documents about this issue. GAO – Gestión Asociada del Local Non- It was established after specific urban Oeste. (Associated Management of governmental problems, particularly, floods in an area of the West) organization. the Maldonado stream. It involves affected (urban neighborhoods) people in the production of information, in the surveying and mapping of flood risk and in the elaboration of adaptation and response strategies. Activities have been developed based on FLACSO associated management methodology. Dirección de Medio Ambiente de la In charge of the It is planning to implement an Integral Risk Municipalidad de Avellaneda Monitoring of the Air Management Plan for the area. (Environmental Department of the Quality Plan in Dock Municipality of Avellaneda) Sud REDES, Centro de Estudios sobre Sub-project for the It is a research project that deals with the Ciencia, Desarrollo y Educación survey of citizens' flood problem, among others, considering Superior (Center for Studies on participation the relation between experts and common Science, Development and experiences in science people. Education) and technology
22
ANNEX B5
Report On the use of Eta model. Training course and technical support By Oscar Frumento Activity developed at the Departamento de Ciencias de la Atmósfera y los Océanos Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires June 2002
Introduction The limited area Eta model (see section Model Description) is presented in a modular structure for running on workstation platforms. Model performance results show reliable stability when used exclusively under the restrictive constrain of the fundamental time step and its relation to the horizontal grid spacing over both zonal and meridional direction.
At present, the model is run operationally by NCEP (National Center for Environmental Prediction) for high-resolution short-range forecasts over the US, and it is also in use in many places around the world (for instance, CEPETEC, Brazil). Besides, the Eta model has been used (and is still being used) in universities and research centers in atmospheric and climate studies (Figueroa et al. 1995, Ji et al. 1997, Berbery et al. 2000).
Model description The Eta model is the evolution of an earlier mesoscale model developed in 1972 at the Hydrometeorological Institute and the University of Belgrade by Mesinger and Z. Janjiæ. The main advantage of the model is the treatment of steep mountain slopes by means the so-called "Eta" coordinate (Mesinger, 1984) as a generalization of the sigma coordinate (Phillips, 1957), with the step-like representation of mountains. In addition, the use of the semi-staggered Arakawa (1972) grid preserves the physical properties in the discrete system
The characteristics of the Eta model are the following: Limited area model and grid point model; Defined on semi-staggered Arakawa (1972) E grid; Use a special technique to prevent grid separation (Messinger, 1973; Janjiæ, 1974, 1979; Vasiljeviæ, 1982; Cullen, 1983, 1985); Vertical coordinate is the step-mountain, Eta coordinate, (Mesinger, 1984); Horizontal advection has a built-in nonlinear energy cascade control (Janjiæ, 1984); The model uses split-explicit time difference (Mesinger, 1974, 1977;Janjiæ, 1984).
The physical parameterization consists of: Mellor-Yamada Level 2.5 scheme for the planetary boundary layer (PBL) (Mellor and Yamada 1974, 1982) with improved treatment of the realizability problem (Mesinger, 1993; Janjiæ 1996); Fourth order lateral diffusion scheme with the diffusion coefficient depending on deformation and turbulent kinetic energy;
23 Large-scale precipitation and shallow and deep convection schemes partially modified by Betts and Mille (Betts, 1986; Betts and Miller, 1986; Janjiæ, 1994); NMC version of the GLAS radiation scheme with interactive random overlap clouds (Davies, 1982; Harshvardhan and Corsetti, 1984); Prognostic cloud water/ice scheme (Zhao and Carr, 1997).
In order to ensure portability, the model code was written following as far as possible the standard ANSI FORTRAN 77 (the most recent version of code permits runs on machines with more than one processor, the linking code being written in FORTRAN 90). A detailed description of Eta model can be found in Lazic (1990).
Training The main goal of the course was to train professionals on the use of the Eta model, providing appropriate technical support for handling and managing input and output data. Furthermore, current possibilities to model and simulate the atmospheric flow at the regional scale under different spatial resolutions, as well as the integration of global on-line available data sets were described. Finally, results and the graphical representation of selected experiments performed by the participants were discussed.
The training course was intended for graduate or advanced students belonging to the field of atmospheric sciences or similar; knowledge of FORTRAN programming and UNIX tools as well as GraDS display system knowledge was required.
Participants: Dr. Rubén Bejaran (Departamento de Ciencias de la Atmósfera y los Océanos) Dr. Moira Doyle (Departamento de Ciencias de la Atmósfera y los Océanos) Dr. Gustavo Escobar (Departamento de Ciencias de la Atmósfera y los Océanos) Students Mr. Carlos Zotelo Miss.Romina Mezher
Activities were divided into two modules, each covering a period of two weeks. First module: Introduction to UNIX PL commands Description of Eta model Directory structure Description of subdirectories Construction of input files from NCEP Reanalysis Products Description of preprocessing Description of post-processing Experiment design Second module: Simulation of selected extreme events of southeast winds over the Río de la Plata estuary. Comparison of results vs. observations. Graphic representation. Mapping. Description of Eta model for 72 hours forecast, using AVN GCM model products Routine for 72 hours forecast using AVN GCM products for 12:00 GMT. File transfer and decoding. Meteogram and sub-products design.
24 Analysis of intrinsic Eta model variables and their potential use as input in a water balance surface model.
First module Eta programs had been configured for running on both SUN and SG platforms. Participants had been familiarized with UNIX OS commands: starting session, creating, editing, moving, directories and files, launching interactive and batch processes, etc.
A detailed description of directory structure and files was summarized and commented on. This structure is composed by 11 subdirectories, which contain program and input files that the Eta model needs for running experiments.
Include directory contains description of input grid definition, model domain and vertical and horizontal resolution and boundary condition time frequency in which the model is fed by observations. Once defined, it is necessary to compile the structure from the main directory.
Experiments Experiments were designed for two particular cases of synoptic situations over the Argentine region. One of them, with center domain in the north-west of the country, represents the intermittent appearance of a surface low pressure area (BNOA) to the east of the Andes Mountains, near 30° S. The other, is the development of intense southeastern surface wind over the Río de la Plata estuary (SRP) which caused intense flooding over the coastline of Buenos Aires City and its surroundings.
For both events (BNOA and SRP), model domain and input grid files were defined in the following manner:
Model domain (high resolution) (degrees) Input grid (coarse) domain (degrees) Clat Clon 1/2 1/2 H res BN BS BW BE H res dlat dlon BNOA -28 -66 -10 -10 0.25 0 -60 -90 -30 2.5 SRP -35 -57 -10 -10 0.25 0 -60 -90 -30 2.5 being, clat, clon: central latitude and longitude of model domain; 1/2 lat, 1/2 lon: half distance from center of Eta model domain to the south and to the west, respectively; H res: horizontal resolution of Eta model and input grid domain; BN, BS, BW and BE: north, south, west and east boundaries of coarse domain.
Daily NCEP Reanalysis (Kalnay et al. 1996) was use to create the input data of the coarse grid domain. These data are geopotential height, zonal wind speed, meridional wind speed and specific humidity on 10 pressure levels (100, 150, 200, 250, 300, 400, 500, 700, 850, 1000 hPa). This task is performed in grads- bin directory by means of a two-step process:
25 Extracting data from NCEP global archive over the coarse domain, and writing data in binary form as needed by input routines.
The model ran for five days in each experiment with the maximum development of the event in day 2.5. Boundary conditions (input data from coarse grid) were applied each 24 hours. Initial time was considered to be 0:00 GMT.
Participants had to set up the pre-processing of the model and run time parameters in the appropriate way. Once the runs were finished, they had to proceed with the post-processing and the representation of results.
Figures a and b show the 1000 hPa geopotential height of the coarse domain and its corresponding limited area domain, as seen by the Eta model, for Z time 00:00.
(a) (b)
It is possible to note that the coarse field is the same with some high-resolutioncase differences.
Second Module Five extreme events of the development of intense southeastern surface wind over the Río de la Plata estuary (SRP) were simulated over a 5-day period. The main objective of the experiment was to obtain hourly two-dimensional surface wind speed on a reduced domain comprising the Río de la Plata estuary. Such data are necessary for being used as input for a hydrological model of the river basin.
The events are summarized in the following table.
26 Boundary of Event Date Hour of reduced domain maximum S 40.5 E1 06/12/1982 23 N 32.4 E2 06/03/1988 18 E 51.5 E3 12/11/1989 14 W 61.5 E4 31/08/1991 07 E5 16/05/2000 16
Where the hour of the event was at the peak water level at the port of Buenos Aires. Experiments started two days before the day of the maximum development of the event over the Río de la Plata estuary. Results are presented from the second day of simulation. In fact, the recommended procedure is to avoid using results of the 12 first hours of run as a way of avoiding discrepancies between the coarse input data and the subsequent transformation to the high resolution..
Example: Description of the event of December 6, 1982.
The sequence shown below began 18 hours before the maximum development of the event. The event was associated with the irruption of a migratory anticyclone moving from the southwest of Buenos Aires province to the northeast (Fig. a). The displacement of the high system produced a gradual increase of wind intensity over the river basin, accompanied with an associated gentle rotation of wind direction to the east (Fig. B and c). From hour 23, the wind started to reduce its intensity, simultaneously with the occurrence of the maximum rise of the river level. It is also noticeable that wind blows inland at this stage (Fig. d). Figures e and f show the slow displacement of the anticyclonic system to the north, and an associate weak wind field over the study area 6 and 12 hours after the maximum event.
27
References Arakawa, A. (1972). Design of the UCLA general circulation model, Numerical Simulation of Weather and Climate, Dept. of Meteorology, Univ. of California, Los Angeles, Techn. Rept. 7, 116pp. Berbery, H. and Collini, E.A. (2000). Springtime precipitation and water vapour flux over southeastern South America. Mon. Wea. Rev., 128, 1328-1346. Betts, A.K. (1986). A new convective adjustment scheme. Part I: Observational and theoretical basis. Quart. J. R. Met. Soc., 112, 677-691. Betts, A.K. and Miller, M.J. (1986). A new convective adjustment scheme. Part II: Single column tests using GATE wave, BOMEX, ATEX and Antarctic air-mass data sets. Quart. J. R. Met. Soc., 112, 693- 709. Cullen, M.J.P. (1983). Current progress and prospects in numerical techniques for weather prediction models. J. Comp. Phys., 50, 1-37.
28 Cullen, M.J.P. (1985). Developments in global modeling at the U.K. Meteorological Office. Garp Special Rep., No. 43, WMO, Geneva, I, 83-98. Davies, R. (1982). Documentation of the solar radiation parameterization in the GLAS climate model. NASA Tech. Memo. 83961, 57 pp. Figueroa, S.N., Satyamurty, P., and da Silva Días, P.L.. (1995). Simulations of the summer circulation over the South American Region with an Eta coordinate model. J. Atmos. Sci., 52, 1573-1584. Harshvardhan and Corsetti, D.G. (1984). Long-wave radiation parameterization for the UCLA/GLAS GCM. NASA Tech. Memo. 86072, 48 pp. Janjiæ, Z.I. (1974). A stable centered difference scheme free of two-grid-interval noise. Mon. Wea. Rev., 102, 319-323. Janjiæ, Z.I. (1979). Forward-backward scheme modified to prevent two-grid-interval noise and its applications in sigma coordinate models. Contrib. Atmos. Phys., 52, 69-84. Janjiæ, Z.I. (1984). Non-linear advection schemes and energy cascade on semi-staggered grids. Mon. Wea. Rev., 112, 1234-1245. Janjiæ, Z.I. (1996). The Mellor-Yamada level 2.5 scheme in the NCEP Eta Model. Preprints, 11th Conf. On Numerical Weather Prediction, Norfolk, VA, Amer. Meteor. Soc., 333-334. Ji, Y., and Vernekar, A.D. (1997). Simulation of the Asian summer monsoons of 1987 and 1988 with a regional model nested in a global GCM. J. Climate, 10, 1965-1979. Kalnay, E. and co-authors. (1996). The NCEP/NCAR 40-year Reanalysis project. Bull. Amer. Meteor. Soc., 77, 437-471. Lazic, L., and Telenta, B., (1990). Documentation of the UB/NMC (University of Belgrade and National Meteorological Center, Washington) Eta model. WMO/TD - No. 366, 186pp. Mellor, G.L. and Yamada, T. (1974). A hierarchy of turbulence closure model for planetary boundary layers. J. Atmos. Sci., 31, 1791-1806. Mellor, G.L. and Yamada, T. (1982). Development of a turbulent closure model for geophysical fluid problems. Rev. Geophys. Sci., 20, 851-875. Mesinger, F. (1973). A method for construction of second -order accuracy difference schemes permitting no false two-grid-interval wave in the height field. Tellus, 25, 444-458. Mesinger, F. (1974). An economical explicit scheme which inherently prevents the false two-grid interval wave in the forecast fields. Proc. Symp. on Difference and Spectral Methods for Atmosphere and Ocean Dynamics Problems, Novosibirsk, 17-22 September 1973, Acad. Sci. Novosibirsk, Part II, 18-34. Mesinger, F. (1977). Forward-backward scheme, and its use in a limited are model. Contrib. Atmos. Phys., 50, 200-210. Mesinger, F. (1984). A blocking technique for representation of mountains in atmospheric models. Riv. Meteor. Aeronautica, 44, 195-202. Mesinger, F. (1993). Forecasting upper tropospheric turbulence within the framework of the Mellor- Yamada 2.5 closure. Res. Activities Atmos. Oceanic Modelling Rep. 18, WMO, Geneva, 4.28-4.29. Phillips, N.A. (1957). A coordinate system having some special advantages for numerical forecasting. J. Metero., 14, 184-185. Vasiljeviæ, D. (1982). The effect of Mesinger´s procedure for preventing grid separation on the geostrophic mode. Contrib. Atmos. Phys., 55, 177-181. Zhao, Q. And Carr, F.H. (1997). A prognostic cloud scheme for operational NWP models. Mon. Wea. Rev., 125, 1931-1953.
29 ANNEX B6 (M. Ré and A. Menendez)
EXTENSION OF THE HYDRODYNAMIC MODEL TO COVER THE MARITIME FRONT The inclusion of the maritime front within the hydrodynamic model domain will allow simulation of the generation of storm waves. The extended model is comprehended between latitudes 40.5°S and 32.4°S and longitudes 61.5°W and 51.5°W.
1 Bathymetry The bathymetric data was provided by the National Hydrographic Service (SHN). The coastline was determined by patching the previous model coastline (Jaime & Menéndez 1999) to the ones obtained by digitizing Chart H1 from the SHN. With these data a regular quadrangular grid was built with a size of 2500-m. Thus, the model domain includes 382 x 408 nodes.
2 Boundary conditions The boundary conditions for the model are the discharge of the Río de la Plata tributaries at its head and the tidal wave front that penetrates through the southern border.
In the case of the tributaries it is sufficient to specify a mean daily discharge, as the modulation imposed by the tidal wave does not play a significant role. The annual mean values were adopted and maintained for all times.
The tidal wave at San Blas Bay (40° 33’ S, 62° 14’ W) was taken as representative of the water level at the leftmost point of the southern border. Assuming purely astronomical tide (no winds), the Tidal Table was used to build this wave along 10 days, spanning the period February 8 to 17, 1997, assuming a mean water level of 0.75 m at the above-mentioned station, as shown in Figure 2.1. From this point to the right, the wave front was assumed as plane and advancing towards the north. Its amplitude was decreased exponentially, in view of its Kelvin wave character, as shown in Figure 2.2. The length scale of this attenuation was used as a calibration parameter. The northern border was considered as a non-reflective one, while the eastern border was taken as non-reflective.
2.50
2.00
1.50
1.00
0.50 water level (m) 0.00
-0.50
-1.00 0 24 48 72 96 120 144 168 192 216 240 time (hr)
30 Figure 1 Tidal wave at San Blas Bay
2.00 1.80 1.60 1.40 1.20 1.00 0.80 water level (m) 0.60 0.40 0.20 0.00 0 100 200 300 400 500 600 700 800 900 1000
distance (km)
Figure 2 Tidal wave front at the southern border
3. Calibration The calibration consisted in obtaining a satisfactory agreement between the water levels as predicted by the model and as provided by the Tide Table at six different control stations (Monte Hermoso, Mar del Plata, San Clemente, Buenos Aires, Martín Garcia and Montevideo). The variables used to calibrate the model were the bottom roughness coefficient and the attenuation length and phase of the southern boundary incoming wave.
Three different zonations were tested for the roughness coefficient: one including three zones (Rio de la Plata, Bahia Blanca Bay and the rest of the domain), one including four zones (the coastal zone of Buenos Aires Province was discriminated from the rest of the domain) and one including five zones (the Rio de la Plata was divided into an inner and an outer zones). The roughness coefficient values, parameterized in terms of the Manning coefficient, varied in the range of 0.005 to 0.030, with the highest ones used at Bahía Blanca Bay zone and the lower ones in the Rio de la Plata.
Four values for the attenuation length of the incoming wave were tested: 100, 200, 300 and 400 kilometers. The best results were obtained with the last value.
It was necessary to change the phase of the incoming wave as provided by the Tide Table. In addition to the provided initial phase, delays of one, two and three hours were tested. The best fit was obtained with a delay of two hours.
Figures 3 and 4 show results of the preliminary calibration for two stations, while Figure 2.5 presents an instantaneous map of water level contour lines.
31
3.00
2.50
2.00
1.50
1.00
0.50
0.00 water level (m) -0.50
-1.00
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-2.00 120.00 144.00 168.00 192.00 216.00 time (hr) Prediction Model
Figure 3 Pre-calibration results in Monte Hermoso
2.00
1.50
1.00
0.50 water level (m)
0.00
-0.50 120.00 144.00 168.00 192.00 216.00 time (hr) Prediction Model
Figure 4 Pre-calibration results in San Clemente
32
6200000.00
1.80
6100000.00 1.70 1.60 1.50 6000000.00 1.40 1.30 5900000.00 1.20 1.10
5800000.00 1.00 0.90 0.80 5700000.00 0.70 0.60 5600000.00 0.50 0.40
6100000.00 6300000.00 6500000.00 6700000.00 6900000.00
Figure 2.5 Instantaneous water level map at the pre-calibration step
33 ANNEX B7 (I. Camilloni and M. Bidegain)
CLIMATE BASELINES AND SCENARIOS Introduction In order to analyse the outputs of the present climate from the Global Climate Models (GCM), we selected the available SRES-A2 scenarios runs in the Modelle and Daten (MOD) page of IPCC (www.dkrz.de/ipcc/ddc/html/SRES/SRES_all.html). This page has only 4 models available: · HADCM3 (Hadley Centre-UK) · CSIRO-Mk2 (CSIRO-Australia) · NCAR-PCM (NCAR-USA) · CGCM2 (CCCma-Canada)
The first step was the computation of the monthly and annual mean sea level pressure (SLP) and precipitation fields over the South American region defined by the latitudes 20°S to 47°S and the longitudes 45W° to 67°W for the different periods available for each GCM model (see Table 1). SLP was selected as indicator of the observed near-surface atmospheric circulation and used to evaluate the goodness of each GCM to reproduce the regional circulation features. Precipitation in the selected region is also relevant to the project in order to evaluate the contribution of the discharges of the Río de la Plata River tributaries.
Model Period HADCM3 1950-2000 CSIRO-Mk2 1961-2000 NCAR-PCM 1981-2000 CGCM2 1950-2000
Table 1. Periods considered for the computation of the monthly and annual SLP fields for the different GCMs.
Sea level pressure The four models have in general an acceptable agreement with the observed monthly and annual climatology derived from the NCEP/NCAR reanalyses (Kalnay et al, 1996). In general the four models have a systematic error overestimating the SLP values in the region between 0.5 to 5 hPa. Figure 1 shows the annual mean SLP fields obtained from the four GCMs considered and the climatology for the periods indicated in Table 1 is presented in Figure 2.
The location at selected months of the year of the centers of high and low pressure in the region is also important in this analysis. The most relevant pressure systems in Southeaster South America are the South Atlantic High Pressure (SAHP) and the Chaco Low (CL).
The comparison of the monthly (not shown) and annual SLP fields (Figures 1 and 2) shows that the HADCM3 and CSIRO-Mk2 models have the best agreement with the observed SLP fields (position and intensity of the pressure systems and annual cycle)
34 Precipitation The GCM outputs of monthly and annual mean precipitation rate were analyzed only for the models that presented the best performance in representing the SLP fields, i.e. the HADCM3 and CSIRO-Mk2 models. Results from the GCMs were compared to the climatology derived from the NCEP/NCAR reanalyses.
The annual precipitation rate field calculated with the HADCM3 is adequate with maximum and minimum well located but underestimated amounts in the entire region. The results obtained with the CSIRO model are not quite good as the observed maximum in northeastern Argentina is not reflected by the model and as in the case of the HADCM3 model, precipitation rate values are underestimated.
The HADCM3 model shows that the annual cycle of the precipitation rate has a maximum during the austral summertime (December to February) in the same position of the CL. This result is not present in the NCEP/NCAR reanalyses. From July to October the maximum is located at (25ºS, 54ºW) in good agreement with the climatology. (Figures not shown)
In the case of the precipitation rate, it seems that the results from the HADCM3 model are in more agreement with the climatology than the fields obtained with the CSIRO model data.
References Kalnay, E. and Co-authors, 1996. The NCEP/NCAR 40-year Reanalysis Project. Bull. Amer. Meteor. Soc. 77, 437–471.
35 ANNUAL SLP (hPa) ANNUAL SLP (hPa) CCCMA MODEL (PERIOD 1950-2000) HADLEY MODEL (PERIOD 1950-2000)
-20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
ANNUAL SLP (hPa) ANNUAL SLP (hPa) CSIRO MODEL (PERIOD 1961-2000) NCAR MODEL (PERIOD 1981-2000)
-20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
Figure 1. Annual mean SLP fields computed from SRES-A2 GCMs outputs.
36
Figure 2. Annual mean SLP fields derived from the NCEP/NCAR reanalyses for the periods indicated in Table 1.
37
ANNUAL PRECIPITATION RATE (mm/day) PRECIPITATION RATE (mm/day) HADLEY MODEL (PERIOD 1950-2000) CSIRO MODEL (PERIOD 1961-2000)
-20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
Figure 3. Annual mean precipitation rate fields computed from SRES-A2 GCMs outputs.
Figure 4. Annual mean precipitation rate fields derived from the NCEP/NCAR reanalyses for the periods indicated in Table 1.
38 ANNEX B8 (G. Escobar and S. Bischoff)
STATISTICAL ANALYSIS OF THE FLOODS IN THE RIO DE LA PLATA (RP) ARGENTINE COAST Identification of events Task 9 provided dates of occurrence of the greater water levels in the port of Buenos Aires during the period 1951/2000 caused by the wind action. To do so, to the observed water high, was subtracted the predicted astronomical tide. Data from 1962 and 1963 were missing. Data includes the peak high of the meteorological tide, its date and hour, and the lapse of time of the event. Events of high meteorological tide were identified as such when their peak high was more than 2.73m and lasted at least 24 hors. These requirements permit to identify the events with some flood impact on the Argentine coast of the RP.
Statistical analysis When the requirement on the peak high were relaxed to only 1.60 m, the number of cases that met this level increased to 297. This permits to give a statistical context to the extreme events described before. The average observed peak high of these events was 2.56 m, and of the meteorological peak high was 1. 93 m and with an average duration of 47 hours.
OBSERVED WATER LEVEL 100
90
80
70
60
50
40
30
20 NUMBER OF OBSERVATIONS
10 Expected 0 160 180 200 220 240 260 280 300 320 340 360 380 400 420 Normal CENTIMETRES
Fig. 1: Distribution of observed peak highs in Buenos Aires.
39 STORM SURGES 140 130 120 110 100 90 80 70 60 50 40 30 NUMBER OF OBSERVATIONS 20 10 Expected 0 140 160 180 200 220 240 260 280 300 320 340 360 Normal CENTIMETRES Fig. 2: Distribution of the meteorological peak highs in Buenos Aires.
DURATION 180
160
140
120
100
80
60
40 NUMBER OF OBSERVATIONS 20 Expected 0 0 20 40 60 80 100 120 140 160 180 Normal HOURS
Figure 3: Distribution of the duration of the meteorological high-water level events in Buenos Aires
72 cases met the 2.73 m minimum requirement. Figure 4 shows the frequency of cases along the year. There is a higher frequency of events in midsummer (January-February) and a lower frequency in autumn and early winter
40 11
10
9
8
7
6
5
4
3
NUMBER OF OBSERVATIONS 2
1 Expected 0 E F M A M J J A S O N D Normal MONTHS
Fig. 4: Monthly frequency of meteorological flood events in the Río de la Plata
The frequency of events by decades shows a positive trend, doubling the number in the 1990/2000 decade with respect to the 1950/1960 one (Fig. 2). 28 26 24 22 20 18 16 14 12 10 8
NUMBER OF OBSERVATIONS 6 4 2 Expected 0 1950 1960 1970 1980 1990 2000 Normal YEARS
Fig. 5: Decadal frequency of meteorological flood events in the Río de la Plata
The trend is consistent with a similar trend towards the south of the western border of the South Atlantic high.
3. Low-level atmospheric circulation associated to extreme meteorological peak events The fields of the geopotential of the nearest in time to the meteorological peak were composed. The fields were taken from the NCEP/NCAR reanalysis that has a data every six hours. The composite associated to the 72
41 cases indicates that the geopotential 1000 hPa features are dominated by a high-pressure system with center at about 800 Km to the south-west of the RP. This field favours the southeaster winds over the RP and the neighbouring ocean. These cases present also a trend toward a more intense pressure gradient over the RP in the period 1950/2000 (Fig 6).
MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1951 / 2000 MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1951 / 1960 -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1991 / 2000 -20
-25
-30
-35
-40
-45
-50
-55
-60 -80 -75 -70 -65 -60 -55 -50 -45 -40
Fig. 6
Variability of the associated low-level atmospheric fields Principal component analysis of the geopotential fields associated to these 72 greatest water levels. Shows that three modes account for more than 75 % of the variance. The first mode represents the case of a migratory anticyclone that when located west of the RP induces southern winds over the river (Fig 7). The second mode represents the case of a very deep perturbation of the mean flow with a strong and huge anticyclone entering from the southern tip of the continent (Fig. 8). In these cases, the anticyclone migrates slower than the average anticyclones and favours the south to southeaster wind component over the RP. Finally, the third mode is typical of a cyclogenesis north of the RP and produces the more intense southeaster winds over the RP. (Fig. 9)
42
GEOPOTENTIAL HEIGHT AT 1000 hPa - 12/10/66 GEOPOTENTIAL HEIGHT AT 1000 hPa - 08/03/87
-20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
Fig. 7 Fig. 8
GEOPOTENTIAL HEIGHT AT 1000 hPa - 16/05/00
-20
-25
-30
-35
-40
-45
-50
-55
-60 -80 -75 -70 -65 -60 -55 -50 -45 -40
Fig. 9
43 ANNEX B9 (I. Camilloni, V. Barros and M. Caffera)
Most of eastern subtropical SA, about 3.2 x 106 km2, constitutes the La Plata Basin (Fig.1). The two main tributaries are, by far, the Paraná and Uruguay rivers. The Paraná has an important tributary, the Paraguay River. Here, only the issue of the greatest discharges that cause large floods will be addressed.
Figure 1: Río de la Plata Basin. River and gauging stations in the Paraná and Uruguay Rivers mentioned in the text.
Floods in the Uruguay River Compared with the Paraná and Paraguay basins, the Uruguay River basin is relatively small, extending over an area of less than 0.4 x 106 km2. Because of its size, its narrow transverse section and the step terrain, the lag between the river discharge and rainfall takes few days. According to the Direction of Hydrology of Uruguay, the 10-m river height in Salto is considered the evacuation mark. Here, we have taken this mark as indicative of the greatest discharges in the lower basin of the river. Since 1950 there has been 18 events exceeding this height. Most of them persisted for only a week or less, with the exception of two events, in 1983 and 1998 respectively, that were part of flood wave lasting approximately 2 months, and each occurring in the course of the strongest El Niño (EN) events of the century. This indicates that the main discharges are usually caused by synoptic events or by a short succession of them. Inspection of each of these events showed that all of them follow a week of a similar dominant low-level circulation.
The composite of the low-level circulation of the 12 days before the peak of the aforementioned 18 cases is presented in figure 16. In the four days before the peak (Fig. 2c), the average flow from the Northwest over Bolivia and Paraguay converges with a weak component from the north over the Uruguay basin. This
44 circulation pattern is even more intense 12 to 9 days before the peak (Fig. 2a) while 8 to 5 days before the peak (Fig. 2b), the flow from the tropical region is further west. An interpretation of this sequence is that the greatest discharges respond typically to two successive events preceded by a strong warm and humid advection from the north. Between these events, there is an intermediate period, probably caused by a cold frontal passage, which is followed by a period of a few days with the northern flow initially restored over western Argentina and far from the Uruguay basin.
a)
b)
c)
45
Figure 2: Wind at the 925 hPa composites of three 4-day periods. (a) Composites for the 4 days previous to the peak flood date; (b) as in (a) but for the 8th to 5th days; (c) as in (a) but for the 12th to 9th days.
The greatest discharges of the Paraná River Without considering the Paraguay basin, the Paraná River basin covers about half the area of the La Plata Basin. It is usually divided into three sub basins, the Upper Paraná (upstream from the junction with the Grande River), the Middle Paraná (between the junctions with the Grande and the Paraguay rivers) and Lower Paraná (downstream from Corrientes) basins (Fig 1). Most of the Paraná River streamflow comes from the upper and middle courses, having a relatively small contribution in its lower section. The high streamflows in the Middle Paraná causes floods over large areas of the Lower Paraná even without a significant local contribution in this sub basin. Due to the large size of the Paraná basin, its big discharges and floods persist for months and they are not caused by single synoptic events.
The greatest monthly-averaged discharge anomalies of the twentieth century at Corrientes (the outlet of the Middle Paraná) calculated with respect to the 1931-1980 monthly means are shown in Table 1. These discharges are considerable larger than any possible impact resulting from water management by the upstream dams. In the top ten peaks, anomalies more than doubled the mean annual discharge of the river. The table includes a classification of the events according to the season and the phase of El Niño-Southern Oscillation (ENSO), and the contribution of each of the sub-basins to these major discharge events. In the case of the Upper Paraná and the upper Middle Paraná, the discharge anomalies corresponding to the month previous to the event in Corrientes were also included, due to the possibility of a zero to one-month lag in the streamflows between these locations
The greatest contributions to the major discharge anomalies in Corrientes come from the Middle Paraná. In general, these contributions amount to about two thirds or more of the discharge anomaly computed in Corrientes, and those of the upper part of the Middle Paraná were greater than those of the lower part of the Middle Paraná. The only cases with important contribution from the Upper Paraná occurred during the extraordinary El Niño 1982-1983 event or a few months after its end. The contribution of the Paraguay River to the major discharge anomalies in Corrientes enhances the contribution of the Middle Paraná, although in a relatively low proportion.
46
It can be concluded that, with few exceptions, the major discharge events in the Lower Paraná originate in the Middle Paraná basin, more precisely in the upper part of this basin. This basin is in the middle of the dipole structure of precipitation associated to the South Atlantic Convergence Zone. Thus, the major discharges of the Paraná River are not associated to the intensification of any of the phases associated to this dipole, but probably to other forcings. According to Table 1 the most important forcing, although not the only one, is El Niño. The six greatest peaks occurred during El Niño events, and five of them in the autumn of the year following the beginning of the events, autumn (+). As an illustration of this aspect, figure 3 shows the composite of the precipitation anomaly during the autumn (+) of El Niño events. The magnitude of the anomaly, centred at this basin, almost doubled the mean rainfall in part of the upper Middle Paraná basin.
Figure 3: Composite of rainfall anomalies for March (+) to May (+) of El Niño events that persisted until May (+) in El Niño 3 region.
Table 1. Major discharge anomalies (m3/s) at Corrientes and the corresponding discharge anomalies at the Upper Paraná (Jupiá station) and Paraguay (Puerto Bermejo station) and anomaly contribution to discharges (m3/s) of the upper Middle, lower Middle and Middle Paraná. Previous month discharge or contribution anomaly is indicated in brackets. (0) and (+) stands for El Niño periods as follows: (0) for the onset year of El Niño and (+) for the following year. N/A means no available data. Ne stands for neutral years.
47 Corrientes Upper Upper Middle Lower Middle Middle Paraná Paraguay Date and ENSO phase Paraná Paraná Paraná contribution contribution contribution Jun 1983 Autumn (+) 38335 8505 18058 6121 24179 5635 (5360) (13331) Jun 1992 Autumn (+) 26787 470 10530 11322 21852 4449 (2502) (13301) DDec 1982 Summer (0) 26131 4380 9427 7584 17011 4633 (2273) (9528) Mar 1983 Autumn (+) 24231 8368 8756 3763 12519 3354 (13224) (3648) Jun 1905 Autumn (+) 24153 N/A N/A (N/A) N/A N/A N/A (N/A) May 1998 Autumn (+) 22999 380 (- 9421 8631 18052 4559(*) 994) (16284) OOct 1998 Spring Ne 21006 794 (- 15206 970 16176 4077(*) 434) (12250) Oct 1983 Spring Ne 20451 5914 6363 5980 12343 2235 (5359) (6968) Jul 1982 Winter (0) 18809 2907 9154 3566 12720 3145 (3664) (2939) Feb 1997 Summer Ne 17657 874 12817 (- 2204 15021 1776 (7432) 2023) SSep 1989 Spring Ne 16698 990 8509 3823 12332 3370 (1090) (4490) Sep 1990 Spring Ne 16410 869 7935 5658 13593 1941 (710) (5177) Jan 1912 Summer (0) 15946 N/A N/A (N/A) N/A N/A N/A (N/A) Nov 1997 Spring (0) 15595 1072 9814 1619 11433 3102 (309) (9190) Jan 1966 Summer (0) 15424 3271 2624 6504 9128 3023 (2376) (3754) Sep 1957 Spring (0) 15033 1347 10331 1327 11658 2022 (877) (8449)
48 ANNEX B10
WIND WAVES: REPORT I. PRESENT WAVE CLIMATE IN THE OUTER REGION OF THE RIO DE LA PLATA (RP) (S. Romero and W. Dragani) Introduction The main characteristics of wind waves in the outer region of RP have been assessed by means of a statistical analysis of wave data measured by Hidrovía S.A. with a directional wave recorder Datawell Waverider. The instrument was moored at approximately 35° 40’ S and 55° 50’ W where the mean depth is 17 m. It was programmed to record every 2 hours 40 minutes. This data set represents the single one existing for the RP, and it has already been analysed by Anschutz, 2000. It consists of 11,297 records gathered from June 1996 to November 2001, and it has five gaps, three of them being eight and nine months long. Anschutz (2000, Coastal Wave Meeting, Barcelona) concluded that the wave condition of the place is made up of a combination of "Swell" and "Sea" fronts, with heights of 0.5 to 1.5 meters and peak periods ranging between 4 and 6 seconds if "Sea" prevails or 10 to 12 seconds if "Swell" prevails. Two-peak spectra were typically presented. The frequency separating the "Swell" and "Sea" conditions is approximately 1/6 Hz (T= 6 sec.) It is important to distinguish between these two states in which wind waves can be separated: Sea, when the waves are under the influence of wind in a generating area, generally made up by steeper waves with shorter periods, and Swell, when the waves move out of the generating area and are no longer subjected to significant wind action. They behave much like a free wave, i.e. free from the disturbing force that caused it. The wave parameters used in the present study are: the characteristic height Hmo, computed as four times the squared root of the 20-minute record total variance and the peak period. In practice, Hmo can be considered as the frequently used significant height, Hs. As regards Tp, it corresponds to the peak of the spectrum of instantaneous wave records.
Considering directions, the rule is that waves coming from a certain direction have such wave direction, i.e., waves coming from the SE have a SE wave direction.
Bidimentional distributions of heights and periods (Hmo-Tp) for each of the eight different wave directions N, NE, E, SE, S, SW, W and NW have been carried out for the outer region of the RP. Mean (the most likely ones) as well as maximum conditions have been considered.
Results In this initial report, of the eight bidimentional distributions of Hmo and Tp obtained, only is shown one is shown in Figure 1, although the 8 are discussed. The results indicate that sea and swell conditions were present only in three of the eight wave directions analysed: S, SE, and E, though having different distributions. E wave direction shows a maximum of 200 sea conditions against 100 cases of swell conditions, with periods of approximately 5 sec and 8 sec, and heights of 0.8 to 1.25 m and 0.8 m, respectively.
SE wave direction shows a maximum of 250 swell conditions against 100 cases of sea conditions, with periods of approximately 10 sec and heights of 0.8 m for the former, and approximately 5 sec and 1.25 m for the latter. S wave direction shows 25 swell conditions against a maximum of 100 sea conditions, with periods of approximately 11 sec and 4 sec, and heights of approximately 0.8 m and 1.25 m respectively.
49 The bidimentional distributions for the other five wave directions NE, N, NW, W and SW show only sea conditions, all of them with a similar distribution. A mean period of approximately 4 sec was common in all five directions. Regarding mean heights, 1 m was the most frequent one for NE, N and NW directions, and 1.5 m was the most frequent for the SW and W directions. The most frequent wave direction for the outer RP was SE, followed by E and S with 4646 (41%), 3161 (28%) and 1607 (14%) cases respectively over a total of 11,297 records. SW, W, NW, N and NE were the least frequent wave directions in the data set, with 539 (5%), 420 (4%), 409 (4%), 278 (2%) and 237 (2%) cases, respectively, over a total of 11,297 records. The maximum heights and associated periods for each of the eight analysed directions are given in Table 1. As it can be seen, maximum heights correspond to the E, SE and S wave directions, which as well were associated to the maximum periods. They were followed by the SW maximum. N, NE, W and NW directions presented lower heights with associated shorter periods.
General Wave Maximum Height Associated Period True Direction Direction (m) (sec) (degrees) N 2.41 4.8 0 NE 2.22 5.2 34 E 4.55 11.0 101 SE 4.39 8.7 152 S 4.55 8.8 174 SW 3.80 8.3 203 W 2.71 7.0 253 NW 2.51 6.7 321
Table 1 Maximum heights and associated periods for each of the eight analysed directions
50 24 H-T BIDIMENSIONAL DISTRIBUTION 22 Datawell Waverider - Hidrovía S.A.
20 Latitude: 35° 40' S Longitude: 55° 50'W Depth: 17 m 18 Wave direction: E Events: 3161 Total events: 11297 16 Analysis period: 1996 - 2001
) 14 s d n o c e
s 12 (
d o i r e
P 10
8
6
4
2
0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Height (meters)
Figure 1: Number of cases is contoured at a 50 contour interval. Note that the 5 contour is also included. In this wave direction, the frequency of occurrence is 28%. It shows a maximum of 200 sea conditions against 100 cases of swell conditions, with periods of approximately 5 sec and 8 sec, and heights of 0.8 to 1.25 m and 0.8 m, respectively. The original report contains the other 7 figures.
51