We apply atmospheric methane column retrievals from two
different satellite instruments (Greenhouse gases Observing SATellite – GOSAT; TROPOspheric Monitoring Instrument – TROPOMI) to a regional inversion
framework to quantify East Asian methane emissions for 2019 at
0.5∘ × 0.625∘ horizontal resolution. The goal
is to assess if GOSAT (relatively mature but sparse) and TROPOMI (new and
dense) observations inform consistent methane emissions from East Asia with
identically configured inversions. Comparison of the results from the two
inversions shows similar correction patterns to the prior inventory in
central northern China, central southern China, northeastern China, and Bangladesh,
with less than 2.6 Tg a−1 differences in regional posterior emissions.
The two inversions, however, disagree over some important regions,
particularly in northern India and eastern China. The methane emissions
inferred from GOSAT observations are 7.7 Tg a−1 higher than those from
TROPOMI observations over northern India but 6.4 Tg a−1 lower over eastern
China. The discrepancies between the two inversions are robust against
varied inversion configurations (i.e., assimilation window and error
specifications). We find that the lower methane emissions from eastern China
inferred by the GOSAT inversion are more consistent with independent
ground-based in situ and total column (TCCON) observations, indicating that the
TROPOMI retrievals may have high XCH4 biases in this region. We also
evaluate inversion results against tropospheric aircraft observations over
India during 2012–2014 by using a consistent GOSAT inversion of earlier
years as an intercomparison platform. This indirect evaluation favors lower
methane emissions from northern India inferred by the TROPOMI inversion. We
find that in this case the discrepancy in emission inference is contributed
by differences in data coverage (almost no observations by GOSAT vs. good
spatial coverage by TROPOMI) over the Indo-Gangetic Plain. The two
inversions also differ substantially in their posterior estimates for
northwestern China and neighboring Kazakhstan, which is mainly due to
seasonally varying biases between GOSAT and TROPOMI XCH4 data that
correlate with changes in surface albedo.