Mediterranean Storms (Proceedings of the 4 th EGS Plinius Conference held at Mallorca, Spain, October 2002)  2003 by Universitat de les Illes Balears (Spain) SATELLITE OBSERVATIONS OF HEAVY RAIN PRODUCING STORMS OVER THE MEDITERRANEAN AREA S. Pinori 1,2 , C. Adamo 1,2 , S. Di Michele 1 , S. Dietrich 1 , A. Mugnai 1 , A. Tassa 1 , G.J. Tripoli 3 , E.A. Smith 4 (1) Istituto di Scienze dell'Atmosfera e del Clima, CNR, Roma, Italy e-mail: s.pinori@isac.cnr.it (2) Università di Ferrara, Dipartimento di Fisica, Ferrara, Italy (3) Department of Atmospheric and Oceanic Sciences, University of Wisconsin, Madison, Wisconsin, USA (4) NASA/ Goddard Space Flight Center, Greenbelt, Maryland, USA ABSTRACT Severe weather events occurring in the western Mediterranean area can be studied by using a series of satellites carrying instruments useful to observe the dynamics and the microphysical structure of precipitation systems during their evolution. At present, the principal satellites observing the south Mediterranean basin to analyze the cloud properties and estimate precipitation are: the METEOSAT satellite carrying on board the Visible and Infrared Spin Scan Radiometer (VISSR); the satellites of the U.S. Defense Meteorological Satellite Program (DMSP) series carrying on board the Special Sensor Microwave/Imager (SSM/I) radiometer; the Tropical Rainfall Measuring Mission (TRMM) carrying on board the Precipitation Radar (PR), the TRMM Microwave Imager (TMI) and the Lightning Imaging Sensor (LIS); and the EOS-TERRA satellite with the infrared MODerate–Resolution Imaging Spectroradiometer (MODIS) In this paper, the different and synergic potential of these satellites for studying precipitating systems is analyzed by focusing on the November 2001 flood that occurred in the south-western Mediterranean area. In addition, we will discuss in some detail the potential of new-generation satellites and instruments that are about to become operational or are planned to be launched in the next future. 1 INTRODUCTION Satellite meteorology is rapidly changing since the launch in orbit of new sensors on satellite platforms will shortly provide more and more advanced information on the cloud systems and their physical properties. Satellite data for precipitation studies are crucial over the sea and in regions where rain monitoring from the ground is more difficult (for example on mountainous and coastal regions). The uneven distribution of rain gauges and weather radars and the relative lack of rainfall measurements over the oceans have significantly limited the use of data over extended regions such as the Mediterranean basin. The new sensors not only add new channels to the traditional ones but also they improve the both the spatial and the temporal sampling both in the visible/near infrared than in the microwave spectral range. In this paper the disastrous flooding event occurred on 9-10 November 2001 in Algiers is analyzed from a satellite point of view to underline the capability of the satellite based observation to describe the cloud systems properties and evolution, even in areas where ground measurements are difficult or impossible (such as over the sea and in country where the rain monitoring is not very evolved). 2 THE ALGERIAN EVENT An initial baroclinic instability associated with a large-scale tropopause fold over western Europe was at the origin of the strong rains that affected the west and center of the Algerian country. The meteorological situation on 9 and 10 November 2001 has been characterized by an infiltration of stratospheric air on Spain and then on the Gibraltar Gulf producing heavy rain over the Algerian coasts and the Balearic Islands. The 9 November, the surface condition was dominated by a high pressure area centred south-west of Ireland and a low one centred on the Alpine zone. A cold front is also present on the south-western Europe. At the same time, the 500 hPa situation showed a really different situation with an area of low pressure extending from Scandinavian area to Gibraltar, where are strong winds with velocity until 150 Kts (at 300 hPa). On the 10 November, the upper level situation was the same, characterized by the occlusion of the low pressure area on the Spain and Northern Africa area, while the surface situation changed dramatically: a lowering of the pressure field occurred over the Algerian coasts also at the lower level of the atmosphere (850 and 700 hPa) originating a depression