An Improvement of Carbon Monoxide Retrieval from SCIAMACHY by Using a Cloud Correction Scheme

Abstract

The UV/Vis/near infrared spectrometer SCIAMACHY on board the European ENVISAT satellite is the only one instrument which enables quantitative total column retrieval of atmospheric carbon monoxide (CO) with high sensitivity to the lower troposphere. Although the general selection of SCIAMACHY observations are the measurements with effective cloud fractions below 20%, due to much higher albedo of clouds compared to ground surface, the remaining effects of clouds can still be large (even up to 100%). Since inaccurate corrections will lead to a wrong interpretation of the results, the accurate cloud correction is essential; in this paper we applied a cloud correction scheme which explicitly considers the cloud fraction, cloud top height and surface albedo of individual observations. In this paper, the sensitivity of cloud effect is described and the difference between corrected and uncorrected result is studied.