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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-884
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
11 Nov 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
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 Hocking1 1Met 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
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.

Citation: 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.
John C. Kealy et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Review of Kealy et al.', Anonymous Referee #2, 09 Dec 2016 Printer-friendly Version 
AC1: 'Response to comments from Anonymous Referee #2', John Kealy, 24 Feb 2017 Printer-friendly Version Supplement 
 
RC2: 'Review of Kealy et al.', Anonymous Referee #1, 19 Jan 2017 Printer-friendly Version 
AC2: 'Response to comments from Anonymous Referee #1', John Kealy, 24 Feb 2017 Printer-friendly Version Supplement 
John C. Kealy et al.
John C. Kealy et al.

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Short summary
Using novel methods of cloud detection from aircraft data over the Sahara desert, we evaluate the performance of the Meteosat satellite in measuring cloud properties: namely, the cloud mask and the cloud-top height. We find that the cloud mask can justifiably be used for many applications (such as creating a detailed Saharan cloud climatology), and we also discuss its limitations. As for the cloud-top height, we show that the dataset cannot yet be considered robust in this part of the World.
Using novel methods of cloud detection from aircraft data over the Sahara desert, we evaluate...
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