Daily Precipitation Grids for South America

Abstract

Agridded dataset of historical daily precipitation for South America is now available to the public. We believe this dataset is a substantial improvement over what heretofore has been easily accessible because it contains data from numerous sources. Th ese data have been combined in a simple manner into daily 1° and 2.5° gridded fi elds for the period 1940–2003. Th e data should help to improve our understanding of precipitation variability, a fundamental and diffi cult problem of meteorology and climatology. Rapid spatial and temporal variability of precipitation, even in the absence of topography, makes diagnosis of the regionalto large-scale component extremely challenging. An accurate depiction of precipitation is a fi rst-order requirement for climate studies and model validation. Research into the causes of precipitation variability is seriously impeded by a frequent lack of adequate observational data. A few scattered observations, some of which may be missing at any given time, are unlikely to refl ect actual precipitation behavior. Th ese and other problems, including timeliness of station reports and a nearly complete lack of coverage over the oceans, have prompted a large research eff ort into estimating precipitation via satellite retrievals. Estimates derived from satellite measurements have proved immensely valuable in fi lling gaps in direct observations, and their accuracy improves as research continues. Nonetheless, gauge-based measurements of good quality and suffi cient density provide the most accurate estimate of precipitation over a given area. Further, satellite research has introduced the additional need for gauge-based observations to validate and calibrate the retrievals.