Validation of water vapor profiles from INSAT-3D with AIRS retrievals and ground – Based measurement over India

Abstract An evaluation of water vapor profiles retrieved from a geostationary Indian National Satellite (INSAT-3D) sounder level-2 physical retrieval and its inter comparison with Atmospheric Infrared Sounder(AIRS) L2 Standard Physical Retrieval (AIRS- only) version 6 profiles over the Indian region. This evaluation is carried out on the spatial distribution of correlation coefficient, bias and root-mean-squareerror (RMSE) at each pressure level from surface to 100 hPa during one year period 2016. The results of the inter comparison reveal that water vapor (g/kg) retrievals from the INSAT-3D are in good agreement with the Aqua-AIRS satellite except for a slight degradation over the coastal regions of Arabian Sea and Bay of Bengal below 850 hPa. The degradation performance over the coastal area associated with possibility of undetected clouds and uncertainty in surface emissivity and also it might be attributed to improper bias correction coefficients for brightness temperaturebefore physical retrievals. In addition to it, a similar analysis is carried out to assess the relative performance of INSAT-3D-retrieved relative humidity (%) profiles with respect to 13 Indian Meteorological Department (IMD) radiosondelocations over the Indian subcontinent from January to December 2016. In this analysis, for each station correlation coefficient, bias and their corresponding root-mean-squareerrors (RMSEs) was carried out between INSAT-3D and 13 radiosondelocations. These results demonstrate that the correlation coefficient (0.7), bias (∼5%) and RMSE (10%) that are very good agreement between INSAT-3D and 13 radiosondestations except for degradation performance of above 300 hPa pressure levels at all stations. Overall, these results give a good confidence into the quality and potential of INSAT-3D over Indian region and can be used in weather forecasting and now casting applications.