Retrieval of greenhouse gases from GOSAT and greenhouse gases and carbon monoxide from GOSAT-2 using the FOCAL algorithm

. Recently, the Fast atmOspheric traCe gAs retrievaL (FOCAL) algorithm has been applied to measurements of the Greenhouse gases Observing SATellite (GOSAT) and its successor GOSAT-2. FOCAL has been originally developed for Orbiting Carbon Observatory-2 (OCO-2) retrievals with the focus on the derivation of carbon dioxide ( XCO 2 ). However, depending on the available spectral windows, FOCAL also successfully retrieves total column amounts for other atmospheric species. Here, 5 we show new results from updated GOSAT and GOSAT-2 FOCAL retrievals. The main focus is placed on methane ( XCH 4 ; full physics and proxy product), water vapour ( XH 2 O ) and the relative ratio of semi-heavy water ( HDO ) to water vapour ( δ D ). Due to the extended spectral range of GOSAT-2 it is also possible to derive information on carbon monoxide ( XCO ) and nitrous oxide ( XN 2 O ) for which we also show first results. We also present an update on XCO 2 from both instruments. Compared to the previous product version (v1), the number of valid XCO 2 data could be significantly increased in the 10 updated version (v3.0) by 50% for GOSAT and about a factor of two for GOSAT-2. All FOCAL data products show reasonable spatial distribution and temporal variations. Comparisons with TCCON (Total Carbon Column Observing Network) result in station-to-station biases which are generally in line with the reported TCCON uncertainties. With this updated version of the GOSAT-2 FOCAL data, we provide a first total column average XN 2 O product. Global XN 2 O maps show a gradient from the tropics to higher latitudes in the order of 15 ppb , which can be explained by variations 15 in tropopause height. The new GOSAT-2 XN 2 O product compares well with TCCON. Its station-to-station variability is lower than 2 ppb , which is about the magnitude of the typical N 2 O variations close to the surface. However, both GOSAT-2 and TCCON measurements show that the seasonal variations in the total column average XN 2 O are in the order of 8 ppb peak-to-peak, which can be easily resolved by the GOSAT-2 FOCAL data.