In:
Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 15, No. 11 ( 2022-06-09), p. 3401-3437
Abstract:
Abstract. We show new results from an updated version of the Fast atmOspheric
traCe gAs retrievaL (FOCAL) retrieval method applied to measurements
of the Greenhouse gases Observing SATellite (GOSAT) and its successor
GOSAT-2.
FOCAL was originally developed for estimating the total column carbon
dioxide mixing ratio (XCO2) from spectral measurements made by the
Orbiting Carbon Observatory-2 (OCO-2).
However, depending on the available spectral windows, FOCAL also
successfully retrieves total column amounts for other atmospheric
species and their uncertainties within one single retrieval.
The main focus of the current paper is on methane (XCH4; full-physics and proxy product), water vapour (XH2O) and the
relative ratio of semi-heavy water (HDO) to water vapour
(δD).
Due to the extended spectral range of GOSAT-2, it is also possible to
derive information on carbon monoxide (XCO) and nitrous oxide
(XN2O) for which we also show first results.
We also present an update on XCO2 from both instruments. For XCO2, the new FOCAL retrieval (v3.0) significantly increases
the number of valid data compared with the previous FOCAL retrieval
version (v1) by 50 % for GOSAT and about a factor of 2 for GOSAT-2
due to relaxed pre-screening and improved post-processing.
All v3.0 FOCAL data products show reasonable spatial distribution and
temporal variations.
Comparisons with the Total Carbon Column Observing Network (TCCON) 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 XN2O product.
Global XN2O maps show a gradient from the tropics
to higher latitudes on the order of 15 ppb, which can be
explained by variations in tropopause height.
The new GOSAT-2 XN2O product compares well with TCCON.
Its station-to-station variability is lower than 2 ppb,
which is about the magnitude of the typical
N2O variations close to the surface.
However, both GOSAT-2 and TCCON measurements show that the seasonal
variations in the total column average XN2O are on the order
of 8 ppb peak-to-peak, which can be easily resolved by the GOSAT-2 FOCAL
data.
Noting that only few XN2O measurements from satellites exist so
far, the GOSAT-2 FOCAL product will be a valuable contribution in
this context.
Type of Medium:
Online Resource
ISSN:
1867-8548
DOI:
10.5194/amt-15-3401-2022
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2505596-3
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