Retrieval of cloud parameters from satellite-based reflectance measurements in the ultraviolet and the oxygen A-band

Abstract

We present a new method for the retrieval of cloud fraction, cloud optical thickness and cloud top pressure from measurements of the Global Ozone Monitoring Experiment (GOME) and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), relevant for the, retrieval of trace gas abundances in cloudy atmospheres. The presented algorithm makes use of the measurements of the oxygen A-band between 758 and 770 nm and additionally of measurements in the ultraviolet between 350 and 390 nm. In addition to the cloud parameters, information about the surface reflection is retrieved. It is shown that measurements in the oxygen A-band alone contain significant information about only two cloud parameters. By adding measurements in the ultraviolet, information about cloud fraction, cloud optical thickness, and cloud top pressure can be retrieved. The cloud retrieval algorithm was applied to GOME data, and the results are compared to cloud parameters retrieved from measurements of the Along Track Scanning Radiometer 2 (ATSR-2). The cloud fractions, cloud optical thickness, and cloud top pressures retrieved by our algorithm and the corresponding ATSR-2 values have a median difference of -0.01, 2.5 and -33 hPa, respectively, with 68% confidence intervals of ±0.11, ±7.5 and ±111 hPa, respectively. Copyright 2007 by the American Geophysical Union.