Patrones de Circulación Atmosféricos-Oceánicos a Meso-Escala Vinculados a las Sequías Severas y Extensas en Venezuela

Abstract

Monthly-averaged oceanic and atmospheric variables in the Tropical Atlantic and Pacific Oceans, during the occurrence of extensive droughts in the Venezuelan territory, were studied using the quarterly-timescale Standardized Precipitation Index for the period of 1950-2000. Monthly rainfall time series obtained mainly from the Instituto Nacional de Meteorología e Hidrología were used. The atmospheric set data was extracted from NCEP/NCARs reanalysis I, while the oceanic data set was extracted from the ERSSTV3B product. The most remarkable results were: (1) extensive droughts with a duration of more than 4 months are frequent during the rainy season (June-September), outside this period the extensive droughts can persist until 7 months, whereas the extensive droughts with less than 4 months (dry spells) can occur at any time of the year; (2) extensive droughts throughout the rainy season coincide with significant changes in low, medium and high troposphere such as a strong convective activity over Colombia, La Niña and the presence of colder-than-normal surface temperatures extended across the North Atlantic; (3) extensive droughts outside the rainy season coincide with a stronger El Niño and the presence of warmer-than-normal surface temperatures extended across the North Atlantic; (4) dry spells are more frequent during both El Niño and the presence of colder-than-normal surface temperatures extended across the North Atlantic.