An investigation of extreme daily rainfall in the Mekong River Basin using a gridded precipitation dataset

Abstract

Comparison of APHRODITE gridded daily rainfall data to 185 rain gauges (Thailand, Laos, Vietnam, that were part of the APHRODITE base data), and 6 independent rain gauges in Mae Chem watershed. Spatial averaging in the APHRODITE dataset leads to underestimation of extremes, but can be corrected using bias correction and orographic correction (based on regressions on elevation data at 0.05 deg, or approx 5.6km) _____ABSTRACT: We compared the extreme daily rainfall values of the 5-year return period, estimated by a frequency analysis based on annual maximum rainfall during 1987–2006 from the APHRODITE dataset and rainfall observations from 185 gauges in Thailand, Laos, and Vietnam. It was found that the extreme rainfall values estimated from the APHRODITE dataset are approximately 33–38% less than those estimated from observations at rain gauge stations. When the APHRODITE data were corrected with an appropriate bias correction ratio and elevation factor and then used to estimate extreme daily rainfall, they showed a better match with the extreme daily rainfall estimations from the rain gauge observations. Moreover, our estimations were independently verified with the rainfall observations in the Mae Chaem Watershed (MCW) in Thailand. This study suggests that the APHRODITE dataset can be used to obtain an estimation of the extreme rainfall in the Mekong River countries after proper bias and orographic corrections are made.