Biserial correlation between vorticity field and precipitation: Rainfall diagnosis and prediction

Abstract

This work concerns the examination of a methodology of synoptic climatology, the biserial correlation technique, which allows studying the relationship between atmospheric circulation and precipitation. The physical meaning of biserial correlation fields between variables representing synoptic-scale circulation, particularly vorticity fields, and local precipitation is explored. One purpose is to examine this approach used to link the large-scale circulation and the smaller-scale surface environment, which seems to be simple, efficient and easy to interpret. An analysis based on biserial correlation configurations between 500 hPa vorticity and precipitation takes into account anomalous vorticity gradients including curvature and shear effects to describe some mechanisms favoring the occurrence of rainfall. It is shown that anomalies in the curvature of synoptic systems are largely causing precipitation. Daily precipitation at Córdoba, Argentina is used as an example to illustrate the results. The position of the cyclonic and anticyclonic anomaly centers and the position of the jet streams in association with precipitation may be clearly identified. The analysis is made extensive to heavier rainfall.