Using spaceborne surface soil moisture to constrain satellite precipitation estimates over West Africa

Abstract

This paper describes a methodology to use the passive microwave measurements of the 6.9 GHz bandwidth of the AMSR‐E sensor which is the most sensitive to surface soil moisture, to constrain satellite‐based rainfall estimates over a semi arid region in West‐Africa. The paper focuses on the aptitude of AMSR‐E measurements to inform if rain occurs or not. The study was conducted over a 125 × 100 km 2 region located in Niger where a dense recording raingauge network is available to build an accurate ground‐based 3‐hour rainfall product at the 25 × 20 km 2 resolution. A satellite‐based rainfall product (EPSAT‐SG), based on both infrared and microwave measurements, was compared to the ground‐based rainfall product. It was shown that EPSAT‐SG overestimates by about 30% the total number of rain events during the 2004 and 2006 rainy seasons. A simple methodology based on the AMSR‐E polarization ratio variations related to the surface soil moisture leaded to suppress a large amount of the wrong rain events.