Influence of the “cloud bow” effect in SEVIRI satellite instrument measurements on characterisation of the diurnal cycle of the land-sea contrast of the cloud liquid water path in Northern Europe
V.S. Kostsov, D.V. Ionov, A.B. Andryukova, E.P. Ryabushko
Saint-Petersburg State University, St. Petersburg, Russia
Keywords: cloud liquid water path, troposphere, inhomogeneities of atmospheric parameters, diurnal cycle of atmospheric parameters, remote sensing, meteorological satellite, SEVIRI
Abstract
The information on the cloud liquid water path (LWP) is necessary for many applications including global and regional climate modelling, weather forecasting, and modelling of the hydrological cycle. The results of derivation of the land-sea LWP contrast from satellite measurements of LWP by the SEVIRI (Spinning Enhanced Visible Infra-Red Imager) instrument over land and water bodies in Northern Europe are presented. When studying the diurnal cycle of the LWP contrast for some water bodies, two separate maxima were discovered, which were observed nearly symmetrically relative to noon on the UTC time scale. In most cases, these maxima were present at measurement locations in the Gulf of Riga and in the Gulf of Finland in the Baltic Sea. Presumably, these maxima are an artefact of observations caused by the so-called “cloud bow effect”. Calculations of a scattering angle for the satellite measurements at these locations confirmed this conclusion. The problem of filtering out the data and the problem of analysing the data in case of possible manifestation of this confounding effect are discussed. The proposed approach to data analysis and the results can be used to assess the quality of LWP measurements by SEVIRI in various regions of the globe.
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