ALBERT

Description: [1]  Over the past decade the development of SCIAMACHY retrievals has increased the interest in the use of satellite measurements for studying the global sources and sinks of methane. Meanwhile measurements are becoming available from the more advanced GOSAT. The aim of this study is to investigate the application of GOSAT retrievals to inverse modelling, for which we make use of the TM5-4DVAR inverse modelling framework. Inverse modelling calculations are performed using data from two different retrieval approaches: a full physics [ Butz et al ., 2011; Schepers et al ., 2012] and a lightpath proxy ratio method [ Frankenberg et al ., 2005a; Butz et al ., 2011; Schepers et al ., 2012]. The performance of these inversions is analyzed in comparison with inversions using SCIAMACHY retrievals and measurements from the NOAA-ESRL flask-sampling network. In addition, we compare the inversion results against independent surface, aircraft and total-column measurements. Inversions with GOSAT data show good agreement with surface measurements, whereas for SCIAMACHY a similar performance can only be achieved after significant bias corrections. Some inconsistencies between surface and total column methane remain in the Southern Hemisphere. However, comparisons with measurements from the TCCON in-situ FTS network indicate that those may be caused by systematic model errors rather than by shortcomings in the GOSAT retrievals. The global patterns of methane emissions derived from SCIAMACHY (with bias correction) and GOSAT retrievals are in remarkable agreement and allow an increased resolution of tropical emissions. The satellite inversions increase tropical methane emission by 30 to 60 TgCH 4 /yr compared to initial a priori estimates, partly counterbalanced by reductions in emissions at mid to high latitudes.