DOAS-based methodology to account for cirrus cloud in observations of carbon dioxide from space

HR: 1340h
AN: A13D-1502 [Abstracts]
TI: DOAS-based methodology to account for cirrus cloud in observations of carbon dioxide from space
AU: * Oshchepkov, S
EM: sergey.oshchepkov@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Bril, A
EM: andrey.bril@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Yokota, T
EM: yoko@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AB: This paper concerns development of the retrieval algorithms for the processing of the Greenhouse gases Observing SATellite (GOSAT) data. GOSAT is scheduled to be launched in 2008 to monitor column amounts of CO2 and CH4 gases. A nadir-looking Fourier-Transform Spectrometer (FTS) of Short Wavelength Infrared (SWIR, 1.6 microns and 2 microns) and 0.76 microns oxygen A-band regions will be mounted on GOSAT. We present an original methodology that accounts for thin cloud in carbon dioxide retrievals from space-based reflected sunlight observations in near-infrared regions utilized by GOSAT. This approach involves a reasonable, simple parameterization of the effective transmittance using a set of parameters that describe the path-length modification caused by cloud. The complete retrieval scheme includes the estimation of cloud parameters from the 0.76-microns O2 A-band and from the H2O-saturated area of the 2.0-microns band, as well as the retrieval of the averaged-column CO2 concentration for interpolated cloud parameters at the 1.58- microns band. The proposed methodology offers the advantages of differential optical absorption spectroscopy (DOAS) and provides acceptably accurate CO2 retrievals from cloudy atmosphere. The proposed algorithm offers one of the candidates for cloud detection and characterization in GOSAT operational data processing.
DE: 0321 Cloud/radiation interaction
DE: 0360 Radiation: transmission and scattering
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting