11:00 AM - 1:00 PM
[HTT19-P01] Validation of GOSAT cloud judgements by using multiple satellite data
Keywords:GOSAT, Himawari, CALIPSO-8, cloud judgment, validation
In the retrieval processing of greenhouse gases (GHG) from the TANSO (Thermal and Near Infrared Sensor for Carbon Observation)-FTS (Fourier Transform Spectrometer) on board GOSAT (board Greenhouse Gases Observing Satellite), cloud contaminations in the field of views (FOVs) of TANSO-FTS affect the observed spectra due to scattering and absorption of solar and earth radiations, which makes it difficult to retrieve accurate GHG concentrations from the observed spectra. Therefore, cloud contaminations in the FOVs of TANSO-FTS have been judged by TANSO-CAI (Cloud and Aerosol Imager) and the short-wave infrared (SWIR) band of TANSO-FTS in the daytime and by the TIR (thermal infrared) band of TANSO-FTS in the nighttime. Saitoh and Kitamura [2021] developed a method for detecting cloud contaminations in the FOVs of TANSO-FTS using reflectance and brightness temperature data from AHI (Advanced Himawari Imager) on board Himawari-8 and validated the GOSAT cloud judgements. This study has compared the cloud judgements in the FOVs TANSO-FTS by GOSAT (TANSO-CAI, TANSO-FTS SWIR band, and TIR band), Himawari-8/AHI, and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) on CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to validate their cloud judgements in the TANSO-FTS FOVs.
First, we have compared the cloud judgements of coincident GOSAT, Himawari-8, and CALIPSO observations. We selected all coincident Himawari-8 and CALIPSO data when their center positions were located in the TANSO-FTS FOVs and they were obtained within one minute (Himawari-8) or ten minutes (CALIPSO) before/after TANSO-FTS observations in January, April, July, and October in 2016. Our comparisons in the cloud judgements of TANSO-FTS FOVs among GOSAT, Himawari-8, and CALIPSO data have confirmed that GOSAT cloud judgements can detect optically thin cirrus clouds by adding the detection by the TANSO-FTS SWIR band.
Next, we have compared the cloud judgements of coincident GOSAT and CALIPSO pairs; 323 pairs in total were found in January, April, July, and October in 2016 by adopting the threshold of their time difference within ten minutes. The comparison results showed that the percentage of agreement in the cloud judgements between GOSAT and CALIPSO was high; furthermore, the percentage of their agreements was higher when there were two or more CALIPSO data in the FOVs of TANSO-FTS than the case when there was only one CALIPSO data in the TANSO-FTS FOVs. We have confirmed that the agreements in the cloud judgements between GOSAT/TANSO-FTS TIR band and CALIPSO were as high as 84% in the nighttime over the ocean when there were two or more CALIPSO data in the TANSO-FTS FOVs; however, the TIR band missed low clouds and optically thin cirrus clouds in some observations. In the daytime over the land, GOSAT/TANSO-FTS SWIR band could also detect optically thin cirrus clouds that were observed by CALIPSO.
First, we have compared the cloud judgements of coincident GOSAT, Himawari-8, and CALIPSO observations. We selected all coincident Himawari-8 and CALIPSO data when their center positions were located in the TANSO-FTS FOVs and they were obtained within one minute (Himawari-8) or ten minutes (CALIPSO) before/after TANSO-FTS observations in January, April, July, and October in 2016. Our comparisons in the cloud judgements of TANSO-FTS FOVs among GOSAT, Himawari-8, and CALIPSO data have confirmed that GOSAT cloud judgements can detect optically thin cirrus clouds by adding the detection by the TANSO-FTS SWIR band.
Next, we have compared the cloud judgements of coincident GOSAT and CALIPSO pairs; 323 pairs in total were found in January, April, July, and October in 2016 by adopting the threshold of their time difference within ten minutes. The comparison results showed that the percentage of agreement in the cloud judgements between GOSAT and CALIPSO was high; furthermore, the percentage of their agreements was higher when there were two or more CALIPSO data in the FOVs of TANSO-FTS than the case when there was only one CALIPSO data in the TANSO-FTS FOVs. We have confirmed that the agreements in the cloud judgements between GOSAT/TANSO-FTS TIR band and CALIPSO were as high as 84% in the nighttime over the ocean when there were two or more CALIPSO data in the TANSO-FTS FOVs; however, the TIR band missed low clouds and optically thin cirrus clouds in some observations. In the daytime over the land, GOSAT/TANSO-FTS SWIR band could also detect optically thin cirrus clouds that were observed by CALIPSO.