Long waves around South America and precipitation in Argentina

Abstract

In this paper the position and intensity of the long waves around South America are related to the precipitation in Argentina. For this purpose indices of zonal and meridional circulation as well as of the curvature of geopotential height at 1000 and 500 hPa were selected. The daily 12 UTC analyses from the European Centre for Medium Range Forecast for 1980 to 1988 were used, averaged over at least five days. A strong positive (negative) anomaly of the meridional index at 1000 and 500 hPa is associated with a negative (positive) anomaly of precipitation. Positive (negative) anomalies of the zonal index at both levels are related to negative (positive) deviations of rainfall. Positive (cyclonic) anomalies of the curvature at 500 and 1000 hPa correspond to enhanced precipitation over the central-eastern part of the country, while over the central-western part the correspondence is of opposite sign. Once methods for forecasting long wave behaviour are available, including for the region around South America, the results may be used to produce medium-range and long-range forecasts of precipitation anomalies over Argentina.