Intertropical Convergence Zone Variability and your the relation with the hidroclimatology of

Lic. Meteorology and Hydrology Master student University of , Evelyn Quirós1 Professor: Dr. Hugo Hidalgo2

1Institute Costarricians of Electricity

2 Universidad de Costa Rica Escuela de Física San José, Costa Rica

Abstract

• The analysis of the statistics of the variations in position and intensity of the central axis of the Intertropical Convergence Zone (CM-ITCZ) in the different periods of the year, will provide a better understanding of their variability, their relationships oceanic and atmospheric phenomena and with Central America regional hydrology.

• We will use several databases of oceanic and atmospheric data in order to determine through the variations of the center of mass and intensity of the ITCZ when and where the most intense influence (as precipitation surplus or defict) occurs during different times of the year.

Methodology

• The domain-average precipitation from two time series: one north of 11oN and another south of 11oN present contrasts on interannual to interdecadal time scales.

• In order to better understand the north–south precipitation contrasts, their interannual and decadal variations are studied in terms of how strong they depend on the intensity of the ITCZ and how the position of the ITCZ is dependent upon other climatic features such as tropical cyclones and high pressure. When a passes near Central America have noticed two situations: If the ITCZ is weak then the rains on the region are lower than when the ITCZ is well defined.

• Furthermore we are also interested on how the location and intensity of the ITCZ are related to large-scale climatic patterns. Spatial moments (domain average, central latitude, and latitudinal spread) of zonally averaged precipitation anomalies along the Central America and the ocean around this region are analyzed, and each is correlated with global (MJO, SST and other) and local time series.

• The interannual band considered here corresponds to timescales that are particularly strong in tropical climate variations and thus is expected to contain much precipitation variability that is related to El Niño–Southern Oscillation; the decadal scale is defined so as to capture the whole range of long-term climatic variations affecting precipitation in the Central America region associated a the main component of rain in the zone: the ITCZ.

Data • Analyze data of precipitation daily, monthly and annual series of:

• Tropical Rainfall Measuring Mission (TRMM): 3-Hour 0.25 x 0.25 degree TRMM _3B42. Generate series used Mathlab of mass center and number of daily and monthly precipitation. 1998-2011.

• Global Precipitation Climatology Project (GPCP): estimate monthly rainfall on a 2.5-degree global grid from 1979 to the present. The careful combination of satellite-based rainfall estimates.

• Pedreros Precipitation Series : 2.5-degree- 1970-2004.

• By comparison and correlations: We will be use SST, AMO, MJO, Energy Cyclone Index (ACE), Ground data of meteorological stations in Central America (1970-2010). Hydrological data of Costa Rica basins.

Study Scenario Since -10 to 25º N and 100 to 55 ºW. Period 1979-2011.

Problem:

• Knowing the behaviour of the center of mass and the intensity of the ITCZ ​​throughout the year and their interaction with different systems and atmospheric and oceanic phenomena.

In Central America there are distinct dry and wet extreme precipitation patterns resulting in significant economic and human lives losses.

Knowing about the mechanisms of one of the main producers of rain in our region will allow us to better plan for activities affected by the scarcity or abundance of rain, allowing us to minimize losses. It is clear that in this context the variation of the interannual and decadal precipitation plays a large role in the economic and social roles of Central America.

Indirect Effect of a Hurricane. The cyclone moved the ITCZ to north, put this over Central America.

H Rita

ZCIT

The moist air coming since the Pacific, converge with a mountains and to ascend, forms convective clouds which give heavy rain . The air down the mountain to the Caribbean is dry! The clouds and rains are concentrated in the Pacific and Central Valley and fewer clouds over the Caribbean and Northern Zone. The red lines indicate that there is convergence of southwesterly winds against mountains. Divergence in the Caribbean (sky clean in this region)!

This image is an example of a system Central America Flash Flood CAFFG Guidance CAFFG, which runs in the SMH and giving notice to potential flood areas, issued this warning to the day of the involvement of Hurricane Rita. In red some areas of imminent flooding, in yellow possible flooding and green not possible flooding! The stream lines show the North flow , not allowed to northward shift of the ITCZ​​!, not coming the wet Hurricane Beta westerly winds to Pacific . A hurricane position there was not sufficient to produce rains over the Pacific , this north flow given the rains at the Caribbean side and Northern Region.

Flujo de Nortes Direct effect of tropical cyclone Tropical Storm Alma 2008:

Advances

• The movement of the ITCZ ​​is responsible for the dry season and the rainy season for much of Central America and especially in Costa Rica, but also the intensity of this band of cloudiness is a vital factor in the influence and effect on weather systems as tropical cyclones.

• So study the position of Centroid of the ITCZ ​​will reveal the variability of this with events like El Niño or La Niña, with tropical systems and MJO.

• In the paleoclimatic analysis and modeling of global climate change there is a discrepancy between the expected position of the ITCZ during warm climates periods.

PRELIMINARY RESULTS

• The position of central latitude of the ITCZ show more high correlation with the JJA precipitation of north of 11ºN than correlation of lower of 10-7ºN. A working hypothesis is that it is the intensity instead of the position what is more relevant to the variability of the 10-7ºN, precipitation.

Annual Varibility

Latitude CM-ITCZ . 1998-2004 14,00 PEDREROS TRMM GPCP 12,00

10,00

8,00

6,00

Latitude (º) Latitude 4,00

2,00

0,00

5 9 2 7 4 9 2 7 4 9 6 4 1 2 3 4 6 7 8 1 3 4 5 6 8 9 1 2 3 5 6 7 8 1 3 4 5 6 8 9 1 2 3 5 6 7 8 1 2 3 4 5 7 8 9 1 2 3 5 6 7 8 9

12 11 11 10 11 12 10 11 10 11 12 10 12 10 11 12 10 12 10 11 12 -2,00 Months

CM-ITCZ JJA vs ACE 2005 ITCZ north position 11 2006 10 Niño 9 8 ITZC south position High number 7 of Atlantic cyclones 6 Low number of 5 Atlantic Cyclones 4 3 Central America 2 Wet Conditions 1 Central America 0 Dry 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Conditions

ACE JJA Daily precipitation TRMM Data -5 to 25N and 100 to 55 W and daily latitude position of CM-ITCZ

20,00 120,00

100,00

10,00 80,00 mm/day)

Grades º 60,00

0,00 40,00 Precipitation ( Precipitation

20,00

01/01/1999 01/01/2003 01/01/2007 01/01/2000 01/01/2001 01/01/2002 01/01/2004 01/01/2005 01/01/2006 01/01/2008 01/01/2009 01/01/2010 -10,00 01/01/1998 0,00 Time CM_TRMM P_TRMM

Background

• North–South Precipitation Patterns in Western North America on Interannual-to-Decadal Timescales. M.D. Dettinger. D.R. Cayan, H.F. Diaz and D. M. Meko. 1998.

• A shiftting band of rain. J.P. Sachs and C. L. Myhrvol. 2011

• ITCZ rather than ENSO signature for abrupt climate changes across the tropical Pacific? G. Leduc , L.Vidal, K. Tachikawa, E. Bard.

• The Central American Midsummer Drought: Regional Aspects and Large-Scale Forcing. R.J. Small and S. P. De Szoeke. S.P Xie. 2009.