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

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. Three high-resolution reanalysis products-the Modern-Era Retrospective Analysis for Research and Applications (MERRA), the Interim ECMWF Re-Analysis (ERA-Interim), and the NCEP Climate Forecast System Reanalysis (CFSR)-are examined for their effectiveness in reproducing retrospective droughts during the period 1980-2005. All the selected reanalysis products show biases in the monsoon season precipitation and temperature. MERRA, ERA-Interim, and CFSR showed median bias in the monsoon season precipitation (temperature) of 10% (-0.39 degrees C), 34% (-0.21 degrees C), and 11% (-0.44 degrees 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) shown by the observations and by MERRA, ERA-Interim, and CFSR were -0.2% (0.13 degrees C), 26% (-0.42 degrees C), 7% (0.24 degrees C), and -8% (0.54 degrees C), respectively, during the period 1980-2005. Despite the differences in the observed areal extent and severity of drought from 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.