ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-12-11823-2012 Methanol from TES global observations: retrieval algorithm and seasonal and spatial variability Cady-Pereira K. E. 1 Shephard M. W. 2 3 Millet D. B. 4 Luo M. 5 Wells K. C. 4 Xiao Y. 1 Payne V. H. 5 Worden J. 5 Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA Atmospheric and Climate Applications, Inc., East Gwillimbury, Ontario, Canada Environment Canada, Toronto, Ontario, Canada University of Minnesota, Minneapolis-St. Paul, Minnesota, USA Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, USA 08 05 2012 12 5 11823 11859 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/12/11823/2012/acpd-12-11823-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/12/11823/2012/acpd-12-11823-2012.pdf

We present a detailed description of the TES methanol (CH<sub>3</sub>OH) 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.

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