“Easterlies”‐Induced Precipitation In Eastern Patagonia: Seasonal Influences Of Enso's Flavors And Sam

AGOSTA, EDUARDO A.; HURTADO, SANTIAGO I.; MARTIN, PAULA B.

INTERNATIONAL JOURNAL OF CLIMATOLOGY

JOHN WILEY & SONS LTD

Año: 2020

0899-8418

The seasonal influence of the phases of El Niño-Southern Oscillation (ENSO)and of Southern Annular Mode (SAM) on precipitation over eastern Patagoniais examined. Also, their impact in generating persistent daily easterly moistureflux leading to daily precipitation events. The significant signatures of thedrivers on precipitation are found in March?April?May (MAM), June?July?August (JJA) for ENSO and November?December?January (NDJ) for SAM.Over the east coast, precipitation is mainly favoured owing to an overallgrowth of the seasonal mean number of precipitation days (~30%) by centralNiño in JJA and by negative SAM phase in NDJ, and growth of the frequencyof persistent events of daily westward moisture flux (~90%) by eastern Niña inMAM. A great spatial variability shapes the anomalies. Evidence is shown forweakened seasonal westerlies linked to Eastern Pacific Niño in MAM.Enhanced daily easterlies with net daily westward moisture flux in the regionlead to strong daily precipitation. Growth in precipitation intensity in thenortheast coast is also associated with Eastern Pacific Niño in MAM. In theinterior lands, south of 45S, westward moisture flux is increased up to ~200%by negative SAM phase in NDJ. The nature of extratropical low-frequencytransient eddies travelling over the South Pacific will influence the frequencyand intensity of daily local precipitation as well as the persistent westward flux during ENSO events.