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Closed Access item A Case of Convection Development over the Western Mediterranean Sea: A Study through Numerical Simulations

Authors:Homar, Víctor
Ramis, Clemente
Romero, Romualdo
Alonso Oroza, Sergio
García-Moya, J. A.
Alarcón, M.
Issue Date:2-Mar-1999
Citation:Meteorology and Atmospheric Physics 71(3-4): 169-188 (1999)
Abstract:A convective case producing heavy precipitation in the western Mediterranean region, characterized by pro- nounced upper level forcing and main rainfall over the sea, is studied. On the day of the event (September 28 th , 1994), more than 140 mm of precipitation were recorded in coastal lands of eastern Spain, and 180 mm were estimated over the sea with radar data. Synoptically, the case appears to combine warm and moist easterly advection at low levels, typically observed in torrential rainfall events of the region, with a less common strong upper level dynamical forcing. A set of mesoscale numerical simulations using the Hirlam model is performed to investigate the mechanisms responsible for the convection development, and to assess the in¯uence of the orography on the rainfall ®eld. Model output diagnosis indicates that in addition to the lower level forcing, a two-jets interaction is decisive for the triggering and driving of the convection during the event. Moreover, a non-topographic simulation reveals a relatively weak in¯uence of the orography on this event when compared with other similar heavy precipitation cases in eastern Spain. Previous studies have shown an orographic in¯uence of more than 90% on the rainfall whereas in this case about 50% of the precipitation over the area is attributed to the orographic forcing. The study is extended with an analysis of the individual effects of the Atlas and Iberian Peninsula, by means of a factor separation technique. It is shown that the Atlas range induces a redistribution of the precipitation over the Mediterranean, whereas local enhancements can be attributed to the Iberian topography
Publisher version (URL):http://dx.doi.org/10.1007/s007030050054
Appears in Collections:(IMEDEA) Artículos

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