Examination of mean precipitation and moisture transport in reanalysis products over India

Abstract

Different reanalyses have been applied widely for various climate-related researches around the globe. However, the skill of these reanalyses to simulate the precipitation patterns at regional scales needs to be carefully assessed due to their known susceptibility to significant biases and inability to capture extremes, especially over complex climatic regions such as India. Considering the significance of extreme precipitation and flood events, this study attempts to relate atmospheric moisture transport to the occurrence of extreme precipitation events using reanalyses. The performance of six global reanalyses is analysed over India in examining the annual and seasonal precipitation characteristics from 1980 to 2013 using various statistical indices. MERRA-Land reasonably estimated precipitation over India, while NCEP data-sets overestimated significantly. The role of integrated water vapour transport (IVT) in two recent extreme precipitation events i.e. over Mumbai in the year 2005 and over Uttarakhand in 2013 was examined. The results point out to the presence of significantly large amount of atmospheric moisture over the corresponding regions, days before the extreme precipitation events. Analysis of IVT patterns can provide indication for occurrence of extreme precipitation in advance. This study will be helpful in establishing the reliability of reanalyses for hydrological and climate-related applications.