Global distributions of methanol and formic acid retrieved for the first time from the IASI/MetOp thermal infrared sounder 1Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles (U.L.B.), Brussels, Belgium
31 Jan 2011
2UPMC Univ. Paris 06; Université Versailles St-Quentin; CNRS/INSU, LATMOS-IPSL, Paris, France
3Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
*now at: European Commission, Joint Research Centre (JRC), 21027 Ispra, Italy
**These authors are respectively Postdoctoral Researcher and Research Associate with FRS-FNRS, Belgium
Received: 15 Jul 2010 – Published in Atmos. Chem. Phys. Discuss.: 08 Sep 2010 Abstract. Methanol (CH3OH) and formic acid (HCOOH) are among the most
abundant volatile organic compounds present in the atmosphere. In this work, we derive the global
distributions of these two organic species using for the first time the Infrared Atmospheric
Sounding Interferometer (IASI) launched onboard the MetOp-A satellite in 2006.
This paper describes the method used and provides a first critical analysis of
the retrieved products. The retrieval process follows a two-step approach in
which global distributions are first obtained on the basis of a simple radiance
indexing (transformed into brightness temperatures), and then mapped onto column
abundances using suitable conversion factors. For methanol, the factors were
calculated using a complete retrieval approach in selected regions. In the case
of formic acid, a different approach, which uses a set of forward simulations for
representative atmospheres, has been used. In both cases, the main error sources
are carefully determined: the average relative error on the column for both
species is estimated to be about 50%, increasing to about 100% for the
least favorable conditions. The distributions for the year 2009 are discussed
in terms of seasonality and source identification. Time series comparing methanol, formic acid and carbon monoxide in different regions are also presented.
Revised: 14 Jan 2011 – Accepted: 24 Jan 2011 – Published: 31 Jan 2011
Citation: Razavi, A., Karagulian, F., Clarisse, L., Hurtmans, D., Coheur, P. F., Clerbaux, C., Müller, J. F., and Stavrakou, T.: Global distributions of methanol and formic acid retrieved for the first time from the IASI/MetOp thermal infrared sounder, Atmos. Chem. Phys., 11, 857-872, doi:10.5194/acp-11-857-2011, 2011.