Evaluation of the Reanalysis products for the Monsoon Season Droughts in India

Abstract

Drought monitoring in near real time is essential for management of water resources, irrigation planning, and food security. However, lack of availability of quality real-time observations leads to slow decision making and relatively poor natural resources management, especially during and after severe and prolonged droughts. The global reanalysis products that are available in near-real time could be valuable for drought monitoring and assessment. We examine the three high resolution reanalysis products, the Modern Era Retrospective Reanalysis (MERRA), European Center for Medium- Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim), and NCEP Climate Forecast System Reanalysis (CFSR) for their effectiveness to reproduce retrospective droughts during the period of 1980-2005. All the selected reanalysis products show biases in the monsoon season precipitation and temperature. The MERRA, ERA-Interim, and CFSR showed median bias in the monsoon season precipitation (temperature) of 10 (-0.39), 34 (-0.21), and 11 (-0.44) % (°C), respectively. The reanalysis products largely fail to reproduce the observed trends in the monsoon season precipitation and temperature over India. All India median changes in the monsoon season precipitation (temperature) showed by the observed, MERRA, ERA-Interim, and CFSR were -0.2 (0.13), 26 (-0.42), 7 (0.24), and -8 (0.54) % (°C), respectively during the period of 1980-2005. Despite the differences in the observed areal extent and severity of drought to those obtained from the individual reanalysis products, ensemble mean drought indices of different reanalysis products showed better performance for drought assessment during the monsoon season in India.