Atmos. Chem. Phys. Discuss., 12, 11823-11859, 2012
www.atmos-chem-phys-discuss.net/12/11823/2012/
doi:10.5194/acpd-12-11823-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Methanol from TES global observations: retrieval algorithm and seasonal and spatial variability
K. E. Cady-Pereira1, M. W. Shephard2,3, D. B. Millet4, M. Luo5, K. C. Wells4, Y. Xiao1, V. H. Payne5, and J. Worden5
1Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA
2Atmospheric and Climate Applications, Inc., East Gwillimbury, Ontario, Canada
3Environment Canada, Toronto, Ontario, Canada
4University of Minnesota, Minneapolis-St. Paul, Minnesota, USA
5Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, USA

Abstract. We present a detailed description of the TES methanol (CH3OH) retrieval algorithm, along with initial global results showing the seasonal and spatial distribution of methanol in the lower troposphere. The full development of the TES methanol retrieval is described, including microwindow selection, error analysis, and the utilization of a priori and initial guess information provided by the GEOS-Chem chemical transport model. Retrieval simulations and a sensitivity analysis using the developed retrieval strategy show that TES: (i) generally provides between 0.5 and 1.0 pieces of information, (ii) is sensitive in the lower troposphere with peak sensitivity typically occurring between ~900–700 hPa (~1–3 km) at a vertical resolution of ~5 km, (iii) has a limit of detectability between 0.5 and 1.0 ppbv Representative Volume Mixing Ratio (RVMR) depending on the atmospheric conditions, corresponding roughly to a profile with a maximum concentration of at least 1 to 2 ppbv, and (iv) in a simulation environment has a mean bias of 0.16 ppbv and a standard deviation of 0.34 ppbv. Applying the newly-derived TES retrieval globally and comparing the results with corresponding GEOS-Chem output, we find generally consistent large-scale patterns between the two. However, TES often reveals higher methanol concentrations than predicted in the Northern Hemisphere spring, summer and fall. In the Southern Hemisphere, the TES methanol observations indicate a model overestimate over the bulk of South America from December through July, and a model underestimate during the biomass burning season.

Citation: Cady-Pereira, K. E., Shephard, M. W., Millet, D. B., Luo, M., Wells, K. C., Xiao, Y., Payne, V. H., and Worden, J.: Methanol from TES global observations: retrieval algorithm and seasonal and spatial variability, Atmos. Chem. Phys. Discuss., 12, 11823-11859, doi:10.5194/acpd-12-11823-2012, 2012.
 
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