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Comparative analysis of low-Earth orbit (TROPOMI) and geostationary (GeoCARB, GEO-CAPE) satellite instruments for constraining methane emissions on fine regional scales: application to the Southeast US
We conduct Observing System Simulation Experiments (OSSEs) to compare the ability of future satellite measurements of atmospheric methane columns (TROPOMI, GeoCARB, GEO-CAPE) for constraining methane emissions down to the 25 km scale through inverse analyses. The OSSE uses the GEOS-Chem chemical tra...
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Published in: | Atmospheric measurement techniques 2018-11, Vol.11 (12), p.6379-6388 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | We conduct Observing System Simulation Experiments (OSSEs)
to compare the ability of future satellite measurements of atmospheric
methane columns (TROPOMI, GeoCARB, GEO-CAPE) for constraining methane
emissions down to the 25 km scale through inverse analyses. The OSSE uses the
GEOS-Chem chemical transport model (0.25∘×0.3125∘ grid
resolution) in a 1-week simulation for the Southeast US with 216 emission
elements to be optimized through inversion of synthetic satellite
observations. Clouds contaminate 73 %–91 % of the viewing scenes depending on
pixel size. Comparison of GEOS-Chem to Total Carbon Column Observing Network (TCCON) surface-based methane column
observations indicates a model transport error standard deviation of 12 ppb,
larger than the instrument errors when aggregated on the 25 km model grid
scale, and with a temporal error correlation of 6 h. We find that TROPOMI
(7×7 km2 pixels, daily return time) can provide a coarse regional
optimization of methane emissions, comparable to results from an aircraft
campaign (SEAC4RS), and is highly sensitive to cloud cover. The
geostationary instruments can do much better and are less sensitive to cloud
cover, reflecting both their finer pixel resolution and more frequent
observations. The information content from GeoCARB toward constraining
methane emissions increases by 20 %–25 % for each doubling of the GeoCARB
measurement frequency. Temporal error correlation in the transport model
moderates but does not cancel the benefit of more frequent measurements for
geostationary instruments. We find that GeoCARB observing twice a day would
provide 70 % of the information from the nominal GEO-CAPE mission
preformulated by NASA in response to the Decadal Survey of the US National
Research Council. |
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ISSN: | 1867-8548 1867-1381 1867-8548 |
DOI: | 10.5194/amt-11-6379-2018 |