Applicability of AIRS Monthly Mean Atmospheric Water Vapor Profiles over the Tibetan Plateau Region

Abstract

The research explores the applicability of the gridded (level 3) monthly tropospheric water vapor (version 5) profiles from the Atmospheric Infrared Sounder (AIRS) instrument and the Advanced Microwave Sounding Unit (AMSU) on-board the NASA Aqua satellite over the Tibetan Plateau by comparing with carefully-processed radiosonde data. Local correlation analyses indicate that below 200 hPa the AIRS/AMSU monthly water vapor profiles are highly consistent with radiosondes over the whole plateau region, especially in the southeastern part and between 300-600 hPa. Relative deviation analyses further show that the differences between monthly mean AIRS/AMSU water vapor data and radiosondes are in general small below 250 hPa, in particular between 300-600 hPa and in high altitude areas. Combined with a further direct comparison between AIRS water vapor vertical profiles and radiosonde observations averaged over the entire domain, these results suggest that the gridded monthly AIRS water vapor profiles can provide a very good account of spatial patterns and temporal variations in tropospheric water vapor content in the Tibetan Plateau region in particular below 200 hPa. However, differences between AIRS and radiosondes are seen at various levels in particular above the level of 250 hPa. Therefore, for detailed quantitative analyses of water budget in the atmosphere and the entire water cycle, AIRS data may need to be corrected or trained using radiosondes. Two fitting functions are derived for warm and cold seasons, respectively, though seasonal difference is generally small.