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- Title
Observing atmospheric formaldehyde (HCHO) from space: validation and intercomparison of six retrievals from four satellites (OMI, GOME2A, GOME2B, OMPS) with SEAC<sup>4</sup>RS aircraft observations over the Southeast US.
- Authors
Lei Zhu; Jacob, Daniel J.; Kim, Patrick S.; Fisher, Jenny A.; Yu, Karen; Travis, Katherine R.; Mickley, Loretta J.; Yantosca, Robert M.; Sulprizio, Melissa P.; De Smedt, Isabelle; Gonzalez Abad6, Gonzalo; Chance, Kelly; Can Li; Ferrare, Richard; Fried, Alan; Hair, Johnathan W.; Hanisco, Thomsa F.; Richter, Dirk; Scarino, Amy Jo; Walega, James
- Abstract
Formaldehyde (HCHO) column data from satellites are widely used as a proxy for emissions of volatile organic compounds (VOCs), but validation of the data has been extremely limited. Here we use highly accurate HCHO aircraft 25 observations from the NASA SEAC4RS campaign over the Southeast US in August-September 2013 to validate and intercompare six operational and research retrievals of HCHO columns from four different satellite instruments (OMI, GOME2A, GOME2B and OMPS) and three different research groups. The GEOS-Chem chemical transport model provides a common intercomparison platform. We find that all retrievals capture the HCHO maximum over Arkansas and Louisiana, reflecting high emissions of biogenic isoprene, and are consistent in their spatial variability over the Southeast US (r=0.4-0.8 30 on a 0.5°×0.5° grid) as well as their day-to-day variability (r=0.5-0.8). However, all satellite retrievals are biased low in the mean by 20-51%, which would lead to corresponding bias in estimates of isoprene emissions from the satellite data. The smallest bias is for OMI-BIRA, which has the highest corrected slant columns and the lowest scattering weights in its air mass factor (AMF) calculation. Correcting the assumed HCHO vertical profiles (shape factors) used in the AMF calculation would further reduce the bias in the OMI-BIRA data. We conclude that current satellite HCHO data provide a reliable proxy for isoprene emission variability but with a low mean bias due both to the corrected slant columns and the scattering weights used in the retrievals.
- Subjects
FORMALDEHYDE; VOLATILE organic compounds; UNITED States. National Aeronautics &; Space Administration; NATURAL satellite atmospheres; CHEMICAL amplification
- Publication
Atmospheric Chemistry & Physics Discussions, 2016, p1
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acp-2016-162