A 3 year climatology of rainfall characteristics over tropical and subtropical South America based on Tropical Rainfall Measuring Mission precipitation radar data

Tropical Rainfall Measuring Mission precipitation radar data acquired during the period I January 1998 to 31 December 2000 over tropical and subtropical South America were used to evaluate the ability of the PR2A25 algorithm in estimating and modelling some rainfall characteristics near the surface. Harmonic analysis applied to the 3 h mean rain rate images successfully modelled the rainfall dynamics over the study area and revealed the extent and propagation of rain bands from the western and eastern Amazon towards its interior, and from western subtropical South America towards the east. It is suggested that rain bands that originate along the eastern slopes of the Andes Cordillera during the first hours of the day and then propagate towards the Amazon interior are possibly due to the convergence of cold katabatic flows from the Andes with warm and moist air present in the foothills of the mountains. This contrasts with previous studies that propose the propagation of precipitation systems from the eastern Amazon towards the Andes Mountains. As study results are based on precipitation radar data with a low sampling rate this bears significant implications for the conclusions drawn. Therefore, study results should be considered as exploratory more than as definitive. Copyright (C) 2004 Royal Meteorological Society.