 |
| Titel |
Retrieval of atmospheric carbon dioxide and methane from GOSAT data with the photon path length probability density function method |
| VerfasserIn |
Sergey Oshchepkov, Andrey Bril, Tatsuya Yokota, Yukio Yoshida |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088593
|
| Publikation (Nr.) |
 EGU/EGU2014-3411.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Greenhouse Gases Observing Satellite "IBUKI" (GOSAT) is the world’s first spacecraft
to measure the concentrations of carbon dioxide (CO2) and methane (CH4). The satellite has
been operating properly from January 23, 2009. This paper presents retrievals of CO2 and
CH4 from GOSAT data with the photon pathlength probability density function
(PPDF) method that has been developed at the National Institute of Environmental
Studies.
This paper focus on a validation of the retrievals using satellite data during 38 months of
GOSAT operation from June 2009 and ground-based Fourier Transform Spectrometer
measurements from the Total Carbon Column Observing Network (TCCON) as the
reference data for the column-averaged dry air mole fractions of the atmospheric
gases. The TCCON–GOSAT coincidence criteria for validating the satellite-based
retrievals included GOSAT single scan data over land within a 5° radius latitude/
longitude circle centered at each of 12 TCCON stations. The ground-based TCCON
data were mean values measured within plus/minus 1 hour of the GOSAT overpass
time.
We use the latest version of PPDF-based method that retrieves simultaneously gas
abundance and light path modification through the atmosphere. The radiance spectra from all
three GOSAT SWIR bands (0.76 μm; 1.6 μm and 2.0 μm) were used to retrieve CO2 and
basic PPDF parameters that described light path shortening and light path lengthening. The
retrieval state vector also included vertical profile of CO2 mixing ratio; scaling factor of prior
water vapor profile; and stretch factor for adjusting the position of the wave-number
grids. Temperature and surface pressure data were prescribed and provided by Japan
Meteorological Agency. For the methane retrievals we processed radiance spectra in 1.67-μm
absorption band using PPDF parameters derived from simultaneous CO2 and PPDF
retrievals.
In particular, a statistical pairwise comparison between GOSAT and TCCON coincident
measurements of CO2 column abundance (over 3500 GOSAT single scans) performed with
the weighed least squares fit showed a correlation coefficient 0.8; a standard deviation of 1.9
ppm, negative bias of 0.4 ppm; and slope of 1.04 for the slope-intercept form of the linear
regression. After a posteriori bias correction these characteristics were 0.9; 1.65 ppm; 0.01
ppm; and 0.99, respectively. |
|
|
|
|
|
|