Verification of GSMaP Rainfall Estimates over the Central Himalayas

Abstract

This paper verifies satellite-based rainfall data GSMaP_MVK+ with gauge observed rainfall over the Nepal Himalayas. Assessment of the accuracy is done at two levels, firstly for the whole country and secondly for physiographic regions. Verification of daily rainfall at a country level shows that the GSMaP_MVK+ captures the spatial distribution of rainfall well but underestimates with a correlation coefficient 0.79, bias -2.6 and RMSE 4.8 mm day-1 and percentage error of -55%. Verification with physiographic regions show that the GSMaP_MVK+ performs well in flatter terrain with a correlation coefficient of higher than 0.8 and prediction accuracy of 70%; however, performance deteriorates with increase in altitude. In the Mid and High Mountain areas the correlation coefficient is 0.4 with prediction of 40% or less. The results indicate the need for improvement of GSMaP_MVK+ estimates by considering orography in the algorithm or bias adjustment before application in the Himalayas.