Processes leading to heavy precipitation associated with two Mediterranean cyclones observed during the HyMeX SOP1

Abstract

International audienceTwo deep cyclones occurred in the Mediterranean between 25–31 October 2012, during the first Special Observation Period (SOP1) of the Hydrological cycle in Mediterranean Experiment (HyMeX). Both cyclones were associated with extreme rainfall covering a large part of the western Mediterranean Sea, where 24-h accumulated precipitation measurements exceeded 150 mm. We combine complementary observations from airborne radar and lidar systems, ZEUS lightning detection network and meteorological surface stations along with satellite diagnostics on deep convection, for a detailed microphysics and (thermo-)dynamical analysis of the two extreme rainfall cases. In addition, we use operational analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) for analyzing the synoptic conditions and diagnosing strongly ascending air masses in the vicinity of the cyclones, so-called warm conveyor belts (WCBs). The analysis revealed the different physical characteristics of the two cyclones responsible for the extreme rainfalls. Both cyclones were associated with a WCB and a comma cloud, but deep convection, intense lightning and very cold cloud tops occurred only for the first case while the second cyclone was mostly associated with stratiform rainfall, a strong WCB, and only few embedded cells of deep convection

Large‐scale wind and precipitation extremes in the Mediterranean: dynamical aspects of five selected cyclone events

“…It is yet unclear whether shallow or deep convection is often embedded in large‐scale slantwise vertical motion (cf. WCBs, see Flaounas et al , ) and this remains an important open question for further investigation. Generally, with respect to the fraction of precipitation produced by the convection schemes, the cases analysed here can be considered as representative (Funatsu et al , ). The five events studied exemplify the co‐occurrence of different types of high‐impact weather on different spatio‐temporal scales, with their associated mechanisms.…”

“…Madonna et al, 2014), as well as convective precipitation. Furthermore, convection can be embedded within the synopticscale systems, and be accounted for as part of WCB-related precipitation (Flaounas et al, 2015b). Furthermore, the cyclonerelative location of impact due to wind or precipitation is not symmetric.…”

A dynamical link between deep Atlantic extratropical cyclones and intense Mediterranean cyclones

“…This methodology to define WCBs ascent has been previously applied in Flaounas et al . (). The outflow portion of the WCB trajectory is of particular interest, as it is the outflow of the WCBs which might amplify the PV ridges and thus influence wave breaking (e.g., Massacand et al ., , Madonna et al ., ).…”

Initiation and development of a mesoscale convective system in the Ebro River Valley and related heavy precipitation over northeastern Spain during HyMeX IOP 15a

“…The ATR42 flew from the French Mediterranean coast to the Balearic Islands from 0954 to 1256 UTC on 20 October 2012 (black/blue solid line in Figure (a)). LEANDRE 2 allowed measurements of the water vapour mixing ratio (WVMR) profiles with a precision ranging from less than 0.1 g kg −1 at 4.5 km above ground level to less than 0.4 g kg −1 near the surface (on average) for an along‐beam resolution of 150 m (for the details, see Bruneau et al ., , ; Flamant et al ., ; Chazette et al ., ; Di Girolamo et al ., ; Duffourg et al ., ; Flaounas et al ., ; Lee et al ., ).…”