Retrieval of MetOp-A/IASI CO profiles and validation with MOZAIC data

E De Wachter,D Hurtmans,E Le Flochmoën,B Barret,P Nedelec,E Pavelin,J P Cammas,M George,J Hadji-Lazaro,M Matricardi,P.-F Coheur,C Clerbaux

doi:10.5194/amt-5-2843-2012

Abstract

Abstract. The IASI (Infrared Atmospheric Sounding Interferometer) nadir-looking thermal infrared sounder onboard MetOp-A enables the monitoring of atmospheric constituents on a global scale. This paper presents a quality assessment of IASI CO profiles retrieved by the two different retrieval algorithms SOFRID and FORLI, by an intercomparison with airborne in-situ CO profiles from the MOZAIC program for the 2008–2009 period. Lower (surface–480 hPa) and upper tropospheric partial column (480–225 hPa) comparisons as well as profile comparisons are made. The retrieval errors of the IASI products are less than 21% in the lower troposphere and less than 10% in the upper troposphere. A statistical analysis shows similar correlation coefficients for the two retrieval algorithms and smoothed MOZAIC of r ~ 0.8 and r ~ 0.7 in the lower and upper troposphere respectively. Comparison with smoothed MOZAIC data of the temporal variation of the CO profiles at the airports of Frankfurt and Windhoek demonstrates that the IASI products are able to capture the seasonal variability at these sites. At Frankfurt SOFRID (respectively FORLI) is positively biased by 10.5% (13.0%) compared to smoothed MOZAIC in the upper (lower) troposphere, and the limited sensitivity of the IASI instrument to the boundary layer when thermal contrast is low is identified. At Windhoek, the impact of the vegetation fires in Southern Africa from July to November is captured by both SOFRID and FORLI, with an overestimation of the CO background values (fire maxima) by SOFRID (FORLI) by 12.8% (10%). Profile comparisons at Frankfurt and Windhoek show that the largest discrepancies are found between the two IASI products and MOZAIC for the nighttime retrievals.

Highlights

Carbon monoxide (CO) is primarily produced at the surface by biomass burning and fossil fuel combustion
This study presented tropospheric CO profiles retrieved from IASI spectra by two different retrieval algorithms: SOFRID and FORLI
A quality assessment of the retrieved IASI CO products was given by a detailed comparison with airborne observations recorded observations recorded at 30 airports in 2008–2009 within the MOZAIC program

Summary

Introduction

Carbon monoxide (CO) is primarily produced at the surface by biomass burning and fossil fuel combustion. Oxidation of methane (CH4) and non-methane hydrocarbons (NMHC), like isoprene, accounts for nearly half of the global CO production (Brenninkmeijer and Novelli, 2003). The removal of CO is largely (for as much as 90 %) determined by the reaction with the hydroxyl (OH) radical. The remaining 10 % is removed by soils (Brenninkmeijer and Novelli, 2003). Not considered a greenhouse gas, CO has a strong indirect effect on the radiation balance of the atmosphere. Through its reaction with OH, CO largely determines the oxidizing capacity of the atmosphere, thereby having a strong impact on the lifetimes of long-lived trace gases (Bergamaschi et al, 2000; Shindell et al, 2009).

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