Improving the Consistency in Water Availability between Different Reanalysis Data over South Asia

Abstract:

The main hindrance behind proper modeling of monsoon in the South Asian region is the lack of accurate date for the major processes involved in moisture budget, like the precipitation and evaporation. As the part of precipitation which remains after evaporation is available on land, their difference, P-E can be considered as a measure of water availability. Even though reanalysis data sets provide values for precipitation and evaporation, the inconsistency between different reanalysis data sets on their values in the study region makes it unreliable for modeling purposes. The P-E values were therefore computed from the atmospheric moisture budget, and on estimating the correlation coefficients, they were found to be more consistent across the different reanalysis data sets used (MERRA, ERA Interim and CFSRR). The P-E values from CFSRR highly disagree with the other two data sets, which was remarkably improved when derived from atmospheric budget. Improved satellite data like GRACE and CERES were also used to understand the surface moisture budget and energy budget of the region. The P-E values from atmospheric budget were compared with the divergence of latent energy flux from energy budget to check its accuracy. The closure of surface moisture budget however weakened on using the atmospheric budget derived values of P-E. Nevertheless, an improved consistency between different reanalysis data sets on P-E values will help in a better modeling of the monsoon over South Asia.