Seasonal Precipitation and Circulation Pattern in South America Associated with the Pacific Decadal Oscillation in the 1970-2003 Period

Abstract

Several studies have pointed out that sea surface temperature patterns on the Pacific and Atlantic oceans contribute to modulate the atmospheric patterns of South America. The disturbances associated with the Pacific Decadal Oscillation, PDO, reach the entire ocean basin and have the potential to impact the climate of various parts of the globe. In this paper, we sought to characterize the seasonal patterns of circulation and precipitation over South America during the negative and positive phases of the PDO between 1970 and 2003, based on data from the NCEP-NCAR reanalysis I and the Global Precipitation Climatology Center, GPCC. During the negative phase of the PDO, there is an intensification of the trade winds over the northeast of South America and of the northern flow in the central region of the continent, these processes being more intense during the rainy season than in the dry season. During the positive phase of the PDO, there is a weakening of the trade winds in northeastern South America and the northern outflow, but the climatic impact during the rainy season is still more intense than in the dry season. Precipitation data from the GPCC indicate that during the negative phase of the PDO negative precipitation anomalies occur over the center-east of South America and positive anomalies on the southeast region. During the positive phase of the PDO, the pattern of precipitation anomalies is the opposite.