Effect of Some Meteorological Phenomena on the Wind Potential of Baja California

Available online at www.sciencedirect.com ScienceDirect

Energy Procedia 57 ( 2014 ) 1327 – 1336

2013 ISES Solar World Congress Effect of some meteorological phenomena on the wind potential of Baja California

M. Zamoraa,*, A. Lambertb, G. Monteroa

a Instituto de Ingeniería, Universidad Autónoma de Baja California, Calle de la Normal s/n, Col. Insurgentes Este, C.P. 21280, Mexicali, México b Facultad de Ingeniería, Universidad Autónoma de Baja California, Calle Churubusco s/n, Col. Insurgentes Este, C.P. 21280, Mexicali, México

Abstract

The purpose of this paper is to analyze the effect of some meteorological phenomena on the wind potential of Baja California. For this aim, a literature search of the meteorological phenomena known as Santa Ana winds, and of the North American Monsoon, was performed. The presence of them was observed in wind speed and the wind direction time series was obtained from meteorological stations. A filtering method was applied to the data to display more details of each phenomenon. Both the meteors were presented every year, while changing the predominant wind direction and wind speed. The Santa Ana wind increases significant wind speed in short periods of time, and their presence varies from days to weeks, while the North American Monsoon decreases the wind speed, and occurs during the summer for a period of months. The measurements used in research are the automatic stations of Comisión Nacional del Agua, at sites of Tijuana, La Rumorosa, Ensenada, Mexicali and Bahía de los Ángeles.

Keywords: Meteorological phenomena; wind potential; time series;

1876-6102 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and/or peer-review under responsibility of ISES. doi: 10.1016/j.egypro.2014.10.086 1328 M. Zamora et al. / Energy Procedia 57 ( 2014) 1327 – 1336

1. Introduction

An evaluation of the wind power potential in the area of La Rumorosa in Baja California [1] has been taking place, and the results show the optimal conditions for the production of wind power. It is well known that wind is sporadic, and its magnitude changes every day, month and year. Some meteorological phenomena identified in Baja California that form parts of the wind occurrences are the Santa Ana Winds and the North American Monsoon.

The Santa Ana Winds (SAW) are defined as a Foehn wind type, warm and dry, from east to northeast, blowing from the Sierra de Nevada to the south coast of California [2]. If its average speed, in more than four intervals, during the day, is greater than or equal to 20 mph (8.9411 m/s), and there is a change in the relative humidity, with a direction from the northeast quadrant, then it is defined as SAW. The SAW are seasonal events that reach an average occurrence of 20 events a year, with a standard deviation of 5 and a 1.5 days average duration, when they begin to appear in September and end in April, December being the month with more events occurring according to the studies [3].

A monsoon circulation is defined as the change in the direction of the seasonal winds between the continent and the ocean; in other words, during one season of the year, winds circulating from the ocean to the land can be noted, and during another season a turnabout in the direction of the winds will take place [4]. The North American Monsoon, Southwest United States Monsoon, Mexican Monsoon or Arizona Monsoon are some of the names given to this phenomenon, due to the fact of its great territorial expansion, being more evident in the northwest of Mexico [5]. A noticeable increase of rainfall from June to July in the southwest of the United States and the northwest of Mexico are experienced. These summer rains can last to even mid-September [6]. The beginning of the summer rains is related to the humidity flow from the south over the Gulf of California, with the formation of a low-pressure center located in Sonora and Arizona [4].

In this paper it is being shown that the occurrences of the SAW identified in four weather stations in the north part of Baja California, that is, in the automatic station of Tijuana, Ensenada, La Rumorosa and Mexicali, in the 2007-2008 period, as well as the monitoring of the North American Monsoon for the year of 2007 in the stations of Mexicali and Bahía de los Ángeles. In Fig. 1 the locations of the automatic weather stations of the Comisión Nacional del Agua can be found.

Fig. 1. Geographical location of the weather stations used in this paper. M. Zamora et al. / Energy Procedia 57 ( 2014 ) 1327 – 1336 1329

2. Data analysis

2.1 SAW events

For the data analysis, the variables of speed and wind direction were taken into account, as well as the relative humidity at 10 meters over ground level, from the automatic stations of Comisión Nacional del Agua.

According to the reading, the direction of the Santa Ana Winds comes from the northeast quadrant corresponding from 0° to 90°, and the magnitude of the speed for the SAW is greater than or equal to 20 mph [3]. With this input information, a filter will be held to the wind speed, taking as an input the condition of a velocity of 8 m/s, in the stations of Tijuana, Ensenada, La Rumorosa and Mexicali. The time schedules will be displayed in each of these stations, with the average schedules of the wind speed for the September-April period, months in which the Santa Ana Winds appear. In Fig. 2, velocities over the 8 m/s can be noted; and any of these could be a Santa Ana event. The only things to take into account are the direction of the wind and the change in the relative humidity.

WS [m/s] [s] 18 16 14 12 10 8 6 4 2 0

La Rumorosa Tijuana Mexicali Ensenada

Fig. 2. Shows the time schedules of the wind speed for each weather station, starting the period on September 1 of 2007 and ending on April 30 of 2008. . The winds interact with the topography of the coast mountains to generate wind jets that are known as Santa Ana Winds, dry (less than 10% relative humidity), and reaching the 50 m/s [7]. The filter applied on the stations showed that only in the La Rumorosa station, the wind direction coming from the northwest quadrant was consistent. The next step was to find the coincidences with another event that was taking place at the same time in the four stations, in order to check the direction of the wind in the other stations, due to the changing wind directions caused by the terrain.

An event in common was found recorded in the four stations on October 21 with duration of 2.5 days. The registration time for the average of the wind speeds appeared first in the La Rumorosa station, starting at the 11:00 hours UTC, followed by Tijuana at the 16:00 hours, Ensenada at 17:00 and Mexicali 1330 M. Zamora et al. / Energy Procedia 57 ( 2014) 1327 – 1336

at 18:00, as observed in Fig. 3. In every station, at the beginning of the event, there is a direction coming from between 0° and 90° that change in some areas and remain the same in others, for example, the one in La Rumorosa staying consistent during the whole event. In Fig. 4, the wind direction on the four stations can be seen.

WS [m/s] 18 16 14 12 10 8 6 4 2 0 21 22 23 24 La Rumorosa Tijuana Ensenada Mexicali

Fig. 3. Incidence of the winds on the four stations in the north of Baja California.

Degrees 350 300 250 200 150 100 50 0 2 2 2 2 1 2 3 4 La Rumorosa Tijuana Ensenada Mexicali

Fig. 4. Wind direction in the stations during the Santa Ana event on October 21.

Regarding the humidity levels, there is a drop in La Rumorosa from 57% to 9.5% and in Mexicali from 34% to 11%, due to the dryness of the Santa Ana Winds. The data was able to provide the observations for only these two stations, Fig. 5. M. Zamora et al. / Energy Procedia 57 ( 2014 ) 1327 – 1336 1331

% 60

40 RH LR

30 RH MXCLI 20 WS LR

10 WS MXCL 0 2 2 2 2 1 2 3 4

Fig. 5. Relative humidity and wind speed. RH LR: Relative Humidity La Rumorosa; WS MXCL wind speed Mexicali.

The results obtained for the event count on the SAW were gathered only in La Rumorosa, because the wind direction on this station did come from the northeast quadrant, in the case of an event, and it was hard to count the events on the other stations, when the direction was not consistent in the quadrant during the event. In Fig. 6 the results for the number of events, and the length and the range of wind speed can be appreciated. Range is very important, because it is thanks to these speeds that the turbines in the wind farms begin to produce energy, starting from the 3 m/s, and some stop at the 20 m/s. When the Santa Ana Winds appears, the wind speed raises drastically, and therefore, also the production of energy. It has a speed record greater than 8 m/s are which count for 79% of the energy production, meaning that the production of energy in the presence of these winds will be almost of the 80%, at 10 meters above ground level. At 80 meters, the velocity would increase, and so would the wind production.

Number of Events SAW by month Number of Santa Ana Winds Duration events events 6 20 17 5 4 15 3 07 - 08 2 10 1 5 1 0 0 Sep Oct Nov Dec Jan Feb Mar Apr 0 0-1.5 1.5-2.5 2.5-3.5 2007-2008 Days

a) Events SAW. b) Santa Ana Winds Duration .

1332 M. Zamora et al. / Energy Procedia 57 ( 2014) 1327 – 1336

% 64.6 70 2007-2008 60 50 40 30 20.6 20 14.4 10 0.5 0 0 0.0 - 4.0 4.0 - 8.0 8.0 - 12.0 12.0 - 16.0 > = 16

Wind class [m/s]

c) Wind class speed during the presence of SAW. Fig. 6. SAW event results in automatic station La Rumorosa.

The peaks of the SAW events are in December and January, decreasing at the beginning of spring. Common length is 1-3 days, although on extreme occurrences it can last up to 5 days [8]. In point (a) of Fig. 6, there should be more events in December and January, but the results show that they are more common in March and April. There is a correlation between El Niño in winter and SAW. According to Raphael [3], when there are Santa Ana Winds during El Niño in winter, even stronger events could be expected. With regards to our data, during the winter of 2007 and beginnings of 2008 appeared La Niña [9], thus this could have modified the presence of events during the months of December and January.

2.1 North American Monsoon

The east part of the state of Baja California is being affected by the North American Monsoon. This circulation, according to Reyes, begins during the month of May, when rainfall appears in the southwest of Mexico. It intensifies later, and the pattern of rain moves to the northwest, until it gets to Sonora and Arizona, with peaks during the months of July and August. In the summer months (July, August and September), the Sonoran desert, that includes the Peninsula of Baja California, Sonora and Arizona, is peculiar for its heating, and a low superficial atmospheric pressure, which favors the grouping of warm and humid air masses.

According to the months of studies, a realization about the patterns of monthly rainfall during the summer in Mexico from June to September came about, and the analysis of this work will take those months, and study the relative humidity, speed and direction of the wind in the stations of Mexicali and Bahía de los Ángeles. To visualize the behavior of the wind, the compass roses from both these stations were gathered, where the turnabout of the direction of the winds can be observed, according to Fig. 7.

M. Zamora et al. / Energy Procedia 57 ( 2014 ) 1327 – 1336 1333

a) Bahía de los Ángeles: June, July, August and September.

b) Mexicali: June, July, August and September.

Fig. 7. Wind roses in a) Bahía de los Ángeles and b) Mexicali.

As seen on Fig. 7, a turnabout in the direction of the wind starts to take place in both weather stations, influenced by the presence of the NA Monsoon. In Bahía de los Ángeles, this influence begins to occur from June to July, coming from the east quadrants, with a major rate of occurrence from the east in the month of August. And to Mexicali, the wind occurrence comes from the southwest, blowing completely in this direction in the months of July and August.

A study of the distribution of incidences of the wind speed in Bahía de los Ángeles showed that during the month of August, the major percentage of the whole year can be reached with a 29.4% in the range of the 2.1-3.0 m/s, meaning that for this place, the monsoon brings low wind speeds, Fig. 8. For Mexicali in the other hand, in the range of 3-5.7 m/s in the month of July, a 59.3% can be reached, the best one of the year in this range. These months are not the best for these two places in a wind-related sense. In Bahía de los Ángeles, the best month for wind energy production is May with an average velocity of 7.3 m/s, and for Mexicali is April with 3.69 m/s. The appearing of the monsoon in the summer brings these changes in the wind velocity. 1334 M. Zamora et al. / Energy Procedia 57 ( 2014) 1327 – 1336

% 60 53.9

50 WS [m/s] 2.1 - 3.0 40 3.0 - 5.7 29.4 30 5.7 - 8.8 8.8 - 11.1 20 >11

0 Jun BA Jun Mx Jul BA Jul Mx Agost BA Agost Mx Sep BA Sep Mx

Fig. 8. Wind class frequency distribution in Bahía de los Ángeles and Mexicali. BA: Bahía de los Ángeles and Mx: Mexicali.

The inconstancy of the phenomenon has been evaluated in the terms of rainfall, and in the northwest regions of Mexico, specifically in the States of Nayarit, Sinaloa and Sonora, up to 70% of the annual rainfall is reported in the months of July, August and September [6]. The beginning of the monsoon rains in the northwest of Mexico and Arizona matches with the flow of humidity coming from the east and southeast during the month of July [5]. Appearances of humidity have been identified with southern winds along the Gulf of California, possibly related to the rain in Arizona [10].

For the studied places, Mexicali and Bahía de los Ángeles, an increase in the relative humidity can be noted during the months of July and August. In the first station, the humidity levels rise up to 60%, while in the second is 70%. This information is shown in Fig. 9, hourly data (UTC).

% 80 Mx-Jun 70 Mx-Jul 60 Mx-Agost 50 Mx-Sep 40 BA-Jun 30 BA-Jul 20 BA-Agost 10 BA-Sep

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Fig. 9. Data relative humidity hourly (UTC) in Mexicali and Bahía de los Ángeles.

M. Zamora et al. / Energy Procedia 57 ( 2014 ) 1327 – 1336 1335

With the information of Fig. 9, the presence of the monsoon can be confirmed in both places with an increase in the relative humidity.

2.3 The available wind power

The wind power per unit area, P/A or wind power density is:

ଵ ܲȀܣ ൌ ߩܸଷ (1) ଶ

One should note that: 1. - The wind power density is proportional to the density of the air. For standard conditions (sea level, 15qC) the density of air is 1.225 kg/m3. 2. - Power from the wind is proportional to the area swept by the rotor. 3.-The wind power density is proportional to the cube of the wind velocity [12].

The power density was determined before and after each SAW event, and it can be noted, that before the appearing of the event, the average power density was 70.22 W/m². Once the event occurs, the wind speed rises drastically, reaching an hourly density average of 515.63 W/m². It is well known that an event can last for days, but when they appear, they increase on an average of 735%, which is the density of wind power available at a single place. This means that in an average of 20 times a year, the energy available will increase 735% during a short period of time, producing huge amounts of wind power on each event.

3. Conclusions

Differences were found in the frequency, length and time of the year in which the two meteorological phenomena — SAW and North American Monsoon — analyzed in this paper occurs. The SAW appears in winter, brings high speeds, its relative humidity decreases and, specifically for La Rumorosa, the wind direction alternates between 0 and 90°. Meanwhile, the North American Monsoon appears in the summer, brings low speeds, its relative humidity is high and the wind direction alternates between 90 and 135°, according to the data from the Mexicali and Bahía de los Ángeles stations.

The high wind speeds recorded in the Santa Ana events lead to produce more electric energy through the wind turbines because the wind power is in relation to the wind speed cubed. Even when it lasts for days, the wind speeds are high, reaching levels of even 7 m/s and showing a frequency of 18 events in the period of September of 2007 to April of 2008. During the presence of a SAW, the decrease in the relative humidity and the rise in temperature change the air density; but this change is not so relevant when extracting the maximum energy available, as is the rise in the wind speed. In the case of the North American Monsoon, the wind speeds that occur are not high and, in its lengthy four month presence, a predominant direction of the wind coming from the southwest is very noticeable in Mexicali in the months of its maximum frequency.

Both meteorological phenomena appear in the wind regime of Baja California. Further research must be done to plan better the extraction of its wind energies, especially of the SAW, for they increase the wind power and are present in the zone of La Rumorosa — one of the best places to generate wind energy in the state of Baja California. It is of vital importance to know the behavior of these meteorological phenomena in order to understand with more detail their relationship with the Southern Oscillation 1336 M. Zamora et al. / Energy Procedia 57 ( 2014) 1327 – 1336

(ENOS) event, for it seems to have an influence in the upwelling of these phenomena and by modifying their behavior. Said changes might be in the wind speed, which are of our interest for the wind power generation.

Acknowledgements The author thanks the Consejo Nacional de Ciencia y Tecnología (CONACYT) for the support with the PhD scholarship, thanks to which the realization of this paper has been possible. The gratitude is also extended to the Comisión Nacional del Agua (CNA), for the provision and delivery of the meteorological data used in this paper.

References

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