Evaluating CFSR and MERRA Reanalysis Using AIRS, MLS and Radiosonde Vertical Air Temperature and Specific Humidity over India

Vertical structure and propagation of specific humidity and temperature fields are critical to monsoon development and circulation over India. The spatial distribution of tropospheric specific humidity is a strong indicator of the deep convection pattern associated with the Indian summer monsoon rainfall and general circulation. Systematic biases in the climatological distribution of water vapor and temperature are known issues in numerical weather prediction models. Evaluation results of the vertical profiles of atmospheric temperature and water vapor from NOAA's Climate Forecast System Reanalysis (CFSR) and NASA's Modern Era Retrospective analysis for Research and Applications (MERRA) against the two satellite data products from Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit (AIRS/AMSU) and Microwave Limb Sounder (MLS) will be presented. The AIRS/AMSU and MLS are used to obtain vertical profiles of atmospheric temperature and water vapor from surface to 1 mb (AIRS data from 1000 mb – 300mb ; MLS for 250 mb to 1 mb). Monthly means of CFSR and MERRA are evaluated against these satellite data by examining the zonal mean cross sections over Indian land-mass in different seasons. Investigation further reveals that CFSR is consistently cooler in the middle troposphere over Indian land (between 22-28N) than MERRA during winter months. During monsoon season, both the models show near surface warming compared to AIRS observations. Results from selected models from Coupled Model Intercomparison Project (CMIP5) evaluated against reanalysis and satellite dataset to better understand biases over Indian region will also be presented.