Connections between the Intertropical Convergence Zone and other climatic features in Central America

Abstract

This work explores statistical connections between the displacements and strength of the Intertropical Convergence Zone (ITCZ) and the Caribbean Low Level Jet (CLLJ). Indicators of the position and of the strength of the ITCZ include the latitude (LATC) and longitude (LONC) of the center of mass of precipitation and the domain precipitation (Pdomain) in a region bounded by coordinates -10 and 25 degrees latitude and -100 and -55 degrees longitude, respectively. Preliminary analyses show that there is a strong correlation (0.82) between summer (JJA) LATC and JJA CLLJ index, and this correlation is lower in other seasons (0.63 for Autumn, 0.20 for Winter and 0.49 for Spring) . These correlations were verified in the zonal wind composites at 925 hPa for the 5 lowest and 5 highest years of LATC. LONC does not seem to have the same strong relationship with the CLLJ. At daily level, composites show precipitation in the Central America region is influenced by Pdomain, LATC, CLLJ index, and to a less extent to LONC. Composites of Sea Surface Temperature for the 5 years of highest and lowest LATC show some relationship with ENSO, although there is a disproportionate influence of the 1997-98 El Niño that may be affecting the results. There is however a consistent feature: during years of high LATC, there are warm anomalies in the tropical Atlantic off the coast of Venezuela, that are not present during years of low LATC.