Heavy rainfall and flood episodes in Europe are related to cyclogenesis and frontal systems. When cyclones develop in the Mediterranean, often deep convection is associated: large and long lasting cell clusters are forced by larger scale disturbances during the warm season and even Mesoscale Convective Systems are detected. Deep, organized convective systems were studied and their link with cyclonic development in the Mediterranean region was analyzed. We studied a one-month period (25 Aug. - 25 Sep. 1998) when 4 cyclonic episodes and several convective clusters occurred in the Mediterranean. In particular two MCS induced by cyclonic motion are studied (28-29 August, 8-9 September 1998). The analysis is based on Meteosat imagery (IR and WV) and on meteorological conventional data (ECMWF data). We analyzed the PVA (potential vorticity anomalies) at 250 and 200 hPa, in conjunction with the geopotential height at 850 hPa, the wet-bulb potential temperature at 500 and 850 hPa, the relative topography 300-700 hPa, the wind fields and radiosoundings. We proposed and evaluated a conceptual model of develop of such systems in the Mediterranean. The proposed conceptual model consists of two interlocking flows. The first is a radial flux of cold-dry air caused by the coupling of the low pressure at low levels (850 hPa) with the potential vorticity anomaly (tropopause sink) at high levels (250-200 hPa). This flow is visible by a decreasing of the thickness 300-700 hPa. The flux of clod-dry air travels eastward and interacts with the second warm-moist air flux, advected from south-west from the cyclonic rotation. The convection develops within few hundreds kilometers east of the surface low. In fact the dry air pushes the warm-moist air up, triggering new thunderstorms few kilometers ahead. The coupling between the PVA and the pressure low is less marked in the last phase of the system development.
Analysis of two MCS in the Mediterranean induced by cyclonic rotation
PRODI, Franco;CARACCIOLO, Clelia;CAPACCI, Davide
2001
Abstract
Heavy rainfall and flood episodes in Europe are related to cyclogenesis and frontal systems. When cyclones develop in the Mediterranean, often deep convection is associated: large and long lasting cell clusters are forced by larger scale disturbances during the warm season and even Mesoscale Convective Systems are detected. Deep, organized convective systems were studied and their link with cyclonic development in the Mediterranean region was analyzed. We studied a one-month period (25 Aug. - 25 Sep. 1998) when 4 cyclonic episodes and several convective clusters occurred in the Mediterranean. In particular two MCS induced by cyclonic motion are studied (28-29 August, 8-9 September 1998). The analysis is based on Meteosat imagery (IR and WV) and on meteorological conventional data (ECMWF data). We analyzed the PVA (potential vorticity anomalies) at 250 and 200 hPa, in conjunction with the geopotential height at 850 hPa, the wet-bulb potential temperature at 500 and 850 hPa, the relative topography 300-700 hPa, the wind fields and radiosoundings. We proposed and evaluated a conceptual model of develop of such systems in the Mediterranean. The proposed conceptual model consists of two interlocking flows. The first is a radial flux of cold-dry air caused by the coupling of the low pressure at low levels (850 hPa) with the potential vorticity anomaly (tropopause sink) at high levels (250-200 hPa). This flow is visible by a decreasing of the thickness 300-700 hPa. The flux of clod-dry air travels eastward and interacts with the second warm-moist air flux, advected from south-west from the cyclonic rotation. The convection develops within few hundreds kilometers east of the surface low. In fact the dry air pushes the warm-moist air up, triggering new thunderstorms few kilometers ahead. The coupling between the PVA and the pressure low is less marked in the last phase of the system development.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
