HR: 1340h
AN: A13D-1497    [Abstracts]
TI: Feasibility of Monitoring CO2 From ACE-FTS Solar Occultation Instrument
AU: * Foucher, P
EM: pierre-yves.foucher@lmd.polytechnique.fr
AF: Laboratoire de Météorologie Dynamique, Ecole Polytechnique, Palaiseau, 91128, France
AU: Chédin, A
EM: alain.chedin@lmd.polytechnique.fr
AF: Laboratoire de Météorologie Dynamique, Ecole Polytechnique, Palaiseau, 91128, France
AU: Dufour, G
EM: dufour@lisa.univ-paris12.fr
AF: Laboratoire Interuniversitaire des Systèmes Atmosphériques, Faculté des Sciences et Technologies, 61 Avenue du Général de Gaulle, Créteil, 94010, France
AU: Bernath, P
EM: pfb500@york.ac.uk
AF: Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, N2L3G1, Canada
AU: Bernath, P
EM: pfb500@york.ac.uk
AF: Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingdom
AU: Boone, C
EM: cboone@sciborg.uwaterloo.ca
AF: Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, N2L3G1, Canada
AB: Atmospheric carbon dioxide influences Earth global climate. Global measurement of CO₂ distribution in the 6-30 km altitude range should greatly improve our knowledge of the carbon cycle as well as the associated transport problems. In this atmospheric region, CO₂ vertical variations of about 2 to 3% are expected based on in situ measurements. Even more than for other species, retrieving CO₂ profile from space-borne sensor requires a high precision instrument and radiative transfer model. Space-borne solar occultation observations should provide an opportunity to determine carbon dioxide vertical profiles. Among such instruments, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE- FTS) on board SCISAT provides (since 2004) atmospheric transmittances with a spectral resolution of 0.02 cm-1 from 750 to 4400 cm-1, a signal to noise ratio of about 300 (for a large part of the spectrum) and with a vertical resolution of about 3 km. The instrument performs sunset and sunrise measurements with coverage between approximately 85°S and 85°N, and with a majority of observations over higher latitudes. Using the LMD 4A-limb viewing radiative transfer model for the simulation of transmittances measured by ACE- FTS, an optimized set of CO₂ spectral microwindows has been selected with the aim of enhancing the sensitivity to CO₂ and reducing biases resulting from the temperature profile and radiative transfer model uncertainties. The 4A-limb simulations have been satisfactorily compared with the ACE forward model and measurements for the selected microwindows. The retrieval process is constrained by using a priori variance covariance matrices estimated from the chemistry transport model MOZART and aircraft observations for each season for 5 latitude bands. In particular these matrices bring useful constraints for the retrieval of CO₂ profile seasonal variation and CO₂ tropopause gradient. We also will present preliminary results of retrieved CO₂ profiles, their sensitivity to CO₂ microwindows and a priori data. Systematic application to real cases is the next step of this feasibility study.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0368 Troposphere: constituent transport and chemistry
DE: 0428 Carbon cycling (4806)
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting