| Summary: | The impact of the El Niño-Southem Oscillation (ENSO) phenomenon on the annual cycle of Colombia's hydro-climatology is quantified. Results of the NCEP/NCAR Climatic Reanalysis Project are used to compare the annual cycle of diverse variables and to evaluate their behavior during the extreme phases of ENSO. The main circulation mechanisms interacting to reduce rainfall during El Niño are: (1) the weakening of the low-level westerly jet that penetrates from the Pacific Ocean inland Colombia at 5°N, discovered in this work; (2) the reduction of the 700 hPa equatorial easterly jet; (3) the reduction of moisture advection from the Caribbean Sea; (4) the reduction in number and intensity of easterly waves along the tropical north Atlantic; (5) the displacement of the ITCZ to the south-west of its normal position, due to an anomalous Hadley cell over tropical South America, and (6) land-atmosphere feedbacks. Correlation analyses confirm the strong influence of ENSO on rainfall and river discharges anomalies of Colombia, in particular during SON and DJF. Multiple linear regression analysis are used to predict seasonal river discharges, including the influence of ENSO, the influence of the North Atlantic Oscillation, and other large scale phenomena, as well as the hydrological persistence, with promissing results. Se cuantifica el impacto del fenómeno El Niño/Oscilación del Sur (ENSO) sobre el ciclo anual de la hidro-climatología de Colombia. Se usan los datos del Proyecto de Reanálisis Climático de NCEP/NCAR para identificar los mecanismos de la circulación atmosférica y de la interacción tierra-océano-atmósfera durante El Niño, que fundamentalmente son: (1) el debilitamiento de la corriente de chorro superficial del oeste que penetra desde el Océano Pacífico al interior de Colombia por los 5°N, descubierta en este trabajo; (2) el debilitamiento de la corriente de chorro ecuatorial de los 700 hPa; (3) la reducción de advección de humedad desde el Mar Caribe; (4) la reducción en número e intensidad de las ondas ...
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