Tropical precipitation estimated by GPCP and TRMM PR observations

Abstract

In this study, tropical monthly mean precipitation estimated by the latest Global Precipitation Climatology Project (GPCP) version 2 dataset and Tropical Rainfall Measurement Mission Precipitation Radar (TRMM PR) are compared in temporal and spatial scales in order to comprehend tropical rainfall climatologically. Reasons for the rainfall differences derived from both datasets are discussed. Results show that GPCP and TRMM PR datasets present similar distribution patterns over the Tropics but with some differences in amplitude and location. Generally, the average difference over the ocean of about 0.5 mm d⁻¹ is larger than that of about 0.1 mm d⁻¹ over land. Results also show that GPCP tends to underestimate the monthly precipitation over the land region with sparse rain gauges in contrast to regions with a higher density of rain gauge stations. A Probability Distribution Function (PDF) analysis indicates that the GPCP rain rate at its maximum PDF is generally consistent with the TRMM PR rain rate as the latter is less than 8 mm d⁻¹. When the TRMM PR rain rate is greater than 8 mm d⁻¹, the GPCP rain rate at its maximum PDF is less by at least 1 mm d⁻¹compared to TRMM PR estimates. Results also show an absolute bias of less than 1 mm d⁻¹ between the two datasets when the rain rate is less than 10 mm d⁻¹. A large relative bias of the two datasets occurs at weak and heavy rain rates.