Retrieval of cloud-cleared radiances using numerical weather prediction model-analysis and forecast fields for INSAT-3D sounder longwave window channel observations

Abstract

Estimation of cloud-cleared radiances, without utilizing any supplementary sensors for INSAT-3D Sounder InfraRed window observations is presented here. This method utilizes simulated clear sky radiances by radiative transfer for TOVS (RTTOV) tool, with the help of global numerical weather prediction (NWP) models analysis and forecast fields, unlike the previously reported approaches where observations from auxiliary/collocated sensors are used. The validation of these derived cloud-cleared radiances is carried out with the already existing operational Level 2 (L2) cloud-cleared radiances of Atmospheric Infra-Red Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI), where the retrieval is carried out utilizing auxiliary Microwave Sounders. Also, a comparative study with the optimal cloud-clearing technique has been carried out here, where the retrieval is done by utilizing the clear sky radiances by means of collocated high-resolution InfraRed observations with the help of auxiliary sensors. The results indicate the scope and promising potential of this technique towards the future operational endeavor of deriving the cloud-cleared radiances without any assistance of co-existing auxiliary hardware system.