OCEAN AND ATMOSPHERIC FORCING FOR INTERANNUAL RAINFALL VARIABILITY IN ARGENTINEAN BUENOS AIRES REGION

GONZÁLEZ, MARCELA HEBE; ROLLA, ALFREDO

montevideo

Congreso; ; WCRP-Conference for Latin America and the Caribbean, developing, linking, and applying climate knowledge; 2014

wcrp

Some large scale atmospheric forcing are described and then their influence on seasonal Buenos Aires plains rainfall is investigated. The relation between winter, spring, autumn and summer rainfall and some patterns of sea surface temperature (El Niño-Southern Oscillation, the Indian Dipole, the Atlantic Tropical Dipole) are detailed. The influence of circulation patterns (Rossby waves displacing over the Pacific Ocean, regional cyclonic anomalies and the Antarctic Oscillation) are also considered. Results show that the factors which affect precipitation highly depend on the season and the region. The main conclusion is that responses to different forcing depend on the area and the season. Rainfall is favored by warm phase of ENSO in northern and western Buenos Aires in Summer and in southern area in Autumn and Winter. The Modoki Niños affect especially rainfall in central and eastern Buenos Aires in Spring. The positive phase of Indian Dipole is related to precipitation greater than normal in northern Buenos Aires in Summer and in northern and central part in Spring. The negative phase of Atlantic tropical Dipole is associated with relevant rainfall amounts in northeastern Buenos Aires in Winter and in northwestern Buenos Aires in Spring. Negative (positive) phase of Antarctic Oscillation is related to greater than normal rainfall in eastern (central and northwestern) Buenos Aires in Autumn (winter). Low frequency oscillations seem to influence precipitation too. For example, negative phase of Pacific Decadal Oscillation (as it is now present) is associated with rainfall in northern and eastern Buenos Aires in Winter and northern and western Buenos Aires in Spring meanwhile positive phase of Atlantic Multidecadal Oscillation is associated with lower than normal rainfall in northern Buenos Aires in Winter and central and western Buenos Aires in Summer.