Clouds over the summertime Sahara: An evaluation of Met Office
Meteosat retrievals using airborne remote sensing
John C. Kealy1,a, Franco Marenco1, John H. Marsham2,3, Luis Garcia-Carreras2, Pete N. Francis1, Michael C. Cooke1, and James Hocking11Met Office, Exeter, United Kingdom 2School of Earth and Environment, University of Leeds, Leeds, United Kingdom 3National Centre for Atmospheric Science anow at: College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, United Kingdom
Received: 04 Oct 2016 – Accepted for review: 07 Nov 2016 – Discussion started: 11 Nov 2016
Abstract. Novel methods of cloud detection are applied to the unique Fennec aircraft dataset, to evaluate the Met Office derived products on cloud properties over the Sahara based on the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on-board Meteosat. Two cloud mask configurations are considered, as well as the retrievals of cloud-top height, and these products are compared to airborne cloud remote sensing products acquired during the Fennec campaign in June 2011 and June 2012. Most detected clouds (67 % of the total) have a horizontal extent which is smaller than a SEVIRI pixel (3 km × 3 km). We show that, when partially cloud contaminated pixels are included, a match between the SEVIRI and aircraft datasets is found in 80 ± 8 % of the pixels. Moreover, under clear skies the datasets are shown to agree for more than 90 % of the pixels. Cloud-top height retrievals however show large discrepancies over the region, which are ascribed to limiting factors such as the cloud horizontal extent, the derived effective cloud amount, and the absorption by mineral dust.
Kealy, J. C., Marenco, F., Marsham, J. H., Garcia-Carreras, L., Francis, P. N., Cooke, M. C., and Hocking, J.: Clouds over the summertime Sahara: An evaluation of Met Office
Meteosat retrievals using airborne remote sensing, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-884, in review, 2016.