Validation of XCH<sub>4</sub> derived from SWIR spectra of GOSAT TANSO-FTS with aircraft measurement data
Column-averaged dry-air mole fractions of methane (XCH<sub>4</sub>), retrieved from Greenhouse gases Observing SATellite (GOSAT) short-wavelength infrared (SWIR) spectra, were validated by using aircraft measurement data from the National Oceanic and Atmospheric Administration (NOAA), th...
| Main Authors: | , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-09-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/7/2987/2014/amt-7-2987-2014.pdf |
| Summary: | Column-averaged dry-air mole fractions of methane (XCH<sub>4</sub>), retrieved
from Greenhouse gases Observing SATellite (GOSAT) short-wavelength infrared
(SWIR) spectra, were validated by using aircraft measurement data from the
National Oceanic and Atmospheric Administration (NOAA), the US Department
of Energy (DOE), the National Institute for Environmental Studies (NIES),
the HIAPER Pole-to-Pole Observations (HIPPO) program, and the GOSAT
validation aircraft observation campaign over Japan. In the calculation of
XCH<sub>4</sub> from aircraft measurements (aircraft-based XCH<sub>4</sub>), other
satellite data were used for the CH<sub>4</sub> profiles above the tropopause. We
proposed a data-screening scheme for aircraft-based XCH<sub>4</sub> for reliable
validation of GOSAT XCH<sub>4</sub>. Further, we examined the impact of GOSAT SWIR
column averaging kernels (CAK) on the aircraft-based XCH<sub>4</sub> calculation
and found that the difference between aircraft-based XCH<sub>4</sub> with and
without the application of the GOSAT CAK was less than ±9 ppb at
maximum, with an average difference of −0.5 ppb.
<br><br>
We compared GOSAT XCH<sub>4</sub> Ver. 02.00 data retrieved within ±2° or ±5° latitude–longitude boxes centered at
each aircraft measurement site with aircraft-based XCH<sub>4</sub> measured on a
GOSAT overpass day. In general, GOSAT XCH<sub>4</sub> was in good agreement with
aircraft-based XCH<sub>4</sub>. However, over land, the GOSAT data showed a
positive bias of 1.5 ppb (2.0 ppb) with a standard deviation of 14.9 ppb
(16.0 ppb) within the ±2° (±5°) boxes,
and over ocean, the average bias was 4.1 ppb (6.5 ppb) with a standard
deviation of 9.4 ppb (8.8 ppb) within the ±2° (±5°) boxes. In addition, we obtained similar results when we used
an aircraft-based XCH<sub>4</sub> time series obtained by curve fitting with
temporal interpolation for comparison with GOSAT data. |
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| ISSN: | 1867-1381 1867-8548 |