Seasonality of the ENSO-Related Rainfall Variability in Central Chile and Associated Circulation Anomalies

Abstract

The seasonality of the ENSO–rainfall relationship in central Chile (30°–41°S) and associated circulation anomalies are studied using correlation and compositing techniques. During El Niño episodes there is a tendency for the occurrence of above-average precipitation between 30° and 35°S in winter [June–July–August (JJA)] and from 35° to 38°S in late spring [October–November (ON)], while rainfall deficit is typically observed from around 38° to 41°S during the following summer [January–February–March (JFM)], when El Niño reaches its maximum development. Opposite rainfall anomalies are characteristic during La Niña events. This study confirms results from previous investigations indicating that enhanced blocking activity over the Amundsen–Bellingshausen Seas area in the southeastern (SE) Pacific during El Niño is a key feature explaining the wet conditions in winter. It is also shown that the same circulation anomaly explains the relatively wet conditions in late spring in the 35°–38°S region durin... Abstract The seasonality of the ENSO–rainfall relationship in central Chile (30°–41°S) and associated circulation anomalies are studied using correlation and compositing techniques. During El Niño episodes there is a tendency for the occurrence of above-average precipitation between 30° and 35°S in winter [June–July–August (JJA)] and from 35° to 38°S in late spring [October–November (ON)], while rainfall deficit is typically observed from around 38° to 41°S during the following summer [January–February–March (JFM)], when El Niño reaches its maximum development. Opposite rainfall anomalies are characteristic during La Niña events. This study confirms results from previous investigations indicating that enhanced blocking activity over the Amundsen–Bellingshausen Seas area in the southeastern (SE) Pacific during El Niño is a key feature explaining the wet conditions in winter. It is also shown that the same circulation anomaly explains the relatively wet conditions in late spring in the 35°–38°S region durin...