Enhancing Clear Radiance Generation for Geostationary Hyperspectral Infrared Sounder Using High Temporal Resolution Information

With high spatio-temporal resolution geostationary hyperspectral infrared sounder (GeoHIS) observations, monitoring, and predicting rapidly changing weather events are expected to be improved with continuous information of 3D weather cube. However, due to the nature of radiation, clouds prevent an adequate retrieval of atmospheric thermodynamic information under clear-sky conditions due to large uncertainties in the current radiative transfer model. Removing cloud effects from GeoHIS sub-footprint is an alternative approach for enhancing clear radiance generation. Such cloud removal can be achieved through the optimal cloud-clearing (OCC) method, which usually relies on the assumption of atmospheric spatial homogeneity. With high temporal resolution observations from GeoHIS, cloud removal can also be achieved through OCC but using the assumption of temporal homogeneity. This concept was demonstrated using 15-min Geostationary Interferometric Infrared Sounder (GIIRS) observations. The longwave GIIRS clear radiances under partially cloud cover can be effectively produced with observation errors less than 0.02 +/- 0.86 K and 0.04 +/- 0.77 K for 11 and 12 mu m, respectively. With the upcoming high spatio-temporal resolution geostationary (GEO) hyperspectral infrared (IR) sounder (GeoHIS) observations, the monitoring and prediction of rapidly changing weather events are expected to be improved with continuous information of three-dimensional weather cube. However, due to the nature of radiation, clouds obscure quantitative applications because of significant uncertainties in the current radiative transfer model. Therefore, enhancing the generation of clear radiance data under partially cloudy conditions is an important alternative approach to improving the quantitative applications of hyperspectral IR data when dealing with clouds. This enhancement of clear radiances has been achieved for hyperspectral IR sounders using the optimal cloud clearing method, which assumes atmospheric spatial homogeneity. Given the unique advantage of high temporal resolution provided by GeoHIS, it is also possible to execute longwave IR clear radiance enhancement through temporal homogeneity assumption for atmospheric temperature. This concept was demonstrated with 15-min Geostationary Interferometric Infrared Sounder observations in this study and could be used to enhance the quantitative applications of GeoHIS measurements under cloudy sky conditions. GEO hyperspectral IR sounder longwave clear radiances can be generated under partially cloudy conditions using high temporal informationPlacing advanced imager and sounder onboard the same GEO platform could enhance the generation of clear radiance data for geostationary hyperspectral infrared sounder (GeoHIS)The concept can be applied to GeoHIS observations if sub-footprint reference clear data are available from an imager or another source