Comparison between the Large-Scale Environments of Moderate and Intense Precipitating Systems in the Mediterranean Region

Abstract

International audienceA characterization of the large-scale environment associated with precipitating systems in the Mediterranean region, based mainly on NOAA-16 Advanced Microwave Sounding Unit (AMSU) observations from 2001 to 2007, is presented. Channels 5, 7, and 8 of AMSU-A are used to identify upper-level features, while a simple and tractable method, based on combinations of channels 3-5 of AMSU-B and insensitive to land-sea contrast, was used to identify precipitation. Rain occurrence is widespread over the Mediterranean in wintertime while reduced or short lived in the eastern part of the basin in summer. The location of convective precipitation shifts from mostly over land from April to August, to mostly over the sea from September to December. A composite analysis depicting large-scale conditions, for cases of either rain alone or extensive areas of deep convection, is performed for selected locations where the occurrence of intense rainfall was found to be important. In both cases, an upper-level trough is seen to the west of the target area, but for extreme rainfall the trough is narrower and has larger amplitude in all seasons. In general, these troughs are also deeper for extreme rainfall. Based on the European Centre for Medium-Range Weather Forecasts operational analyses, it was found that sea surface temperature anomalies composites for extreme rainfall are often about 1 K warmer, compared to nonconvective precipitation conditions, in the vicinity of the affected area, and the wind speed at 850 hPa is also stronger and usually coming from the sea

An overview of the lightning and atmospheric electricity observations collected in southern France during the HYdrological cycle in Mediterranean EXperiment (HyMeX), Special Observation Period 1

“…Summer electrical activity is predominately located over continental Europe while during the winter the electrical convective clouds are mainly observed over the Mediterranean Sea, as established by climatology based on lightning records (e.g., Holt et al, 2001;Christian et al, 2003;Defer et al, 2005) or on space-based microwave measurements (e.g., Funatsu et al, 2009). Holt et al (2001) Adamo (2004) reported that the flash rates over the Mediterranean Sea are significantly smaller than those recorded at similar latitudes in the United States.…”

Tropical transition of a Mediterranean storm by jet crossing

“…Its geographical location between the Subtropics and the midlatitudes, the complex orography surrounding the Mediterranean Sea, and the large reservoir of sometimes warm water contribute to the formation of a broad continuum of cyclones, from shallow, warmcore to deep, cold-core storms (Campins et al, 2006). Satellite observations show a majority of cloud systems at the mesoscale, only a fraction being associated with an upper-level anomaly and preferentially during the cold season (Chaboureau and Claud, 2006), while deep convection has been sensed over the sea mostly during autumn (Funatsu et al, 2009). Among the Mediterranean cyclones accompanied by upper-level anomalies and deep convection, about 15 mesocyclones have been observed over the last 20 years, preferentially in autumn (Fita et al, 2007).…”

Review Article: Atmospheric conditions inducing extreme precipitation over the eastern and western Mediterranean

“…The Italian and Balkan peninsulas are affected by moisture originating in the MB. In a similar study, Gomez-Hernandez et al (2013) pointed out the west Mediterranean Sea as the dominant moisture source for most MB regions during the wet season.…”

“…An investigation of the link between atmospheric circulation patterns and Iberian total rainfall for the period 1958-1997 led by Goodess and Jones (2002) revealed that the NAO negative mode produces high-pressure blocking in the northeast Atlantic, and a more meridional circulation than the opposite, NAO positive mode, consistent with Moses et al (1987). Moreover, upper-air troughs and incursions of polar air over the Mediterranean are more frequent and the Atlantic storm tracks are displaced south.…”

“…In the EM, the synoptic-scale system responsible for about 90 % of the annual rainfall is an extratropical cyclone -the Cyprus Low (Goldreich, 2003). The surface low over the EM featuring the heaviest rainfall days is generally accompanied by high pressure over the WM (Fig.…”