Cloud cover analysis associated to cut-off low-pressure systems over Europe using Meteosat Imagery |
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| Authors: | G Delgado A Redaño J Lorente R Nieto L Gimeno P Ribera D Barriopedro R García-Herrera A Serrano |
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| Institution: | (1) Departament d’Astronomia i Meteorologia, Universitat de Barcelona, Barcelona, Spain;(2) Facultad de Ciencias de Ourense, Universidad de Vigo, Ourense, Spain;(3) University of Lisbon, CGUL, IDL, Lisbon, Portugal;(4) Departamento de CC Ambientales, Universidad Pablo de Olavide de Sevilla, Sevilla, Spain;(5) Departamento de Física de la Tierra, Astronomía y Astrofísica, Facultad de Físicas, Universidad Complutense de Madrid, Ciudad Universitaria, Madrid, Spain;(6) Departamento de Física, Universidad de Extremadura, Badajoz, Spain |
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| Abstract: | Summary This paper reports a cloud cover analysis of cut-off low pressure systems (COL) using a pattern recognition method applied
to IR and VIS bispectral histograms. 35 COL occurrences were studied over five years (1994–1998). Five cloud types were identified
in COLs, of which high clouds (HCC) and deep convective clouds (DCC) were found to be the most relevant to characterize COL
systems, though not the most numerous.
Cloud cover in a COL is highly dependent on its stage of development, but a higher percentage of cloud cover is always present
in the frontal zone, attributable due to higher amounts of high and deep convective clouds. These general characteristics
are most marked during the first stage (when the amplitude of the geopotencial wave increases) and second stage (characterized
by the development of a cold upper level low), closed cyclonic circulation minimizing differences between rearward and frontal
zones during the third stage. The probability of heavy rains during this stage decreases considerably. The centres of mass
of high and deep convective clouds move towards the COL-axis centre during COL evolution. |
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