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

Abstract

Cyclones impacting the densely populated Mediterranean region have been a continuous research focus, mainly for investigating either the associated heavy precipitation or the damaging wind gusts. In this study we examine five Mediterranean cyclones with combined large‐scale impact of strong 10 m gusts and heavy precipitation. The selected events occurred in (i) December 2003 in the northeastern Mediterranean; (ii) October 2007 in the central Mediterranean; (iii) January 2009, known as storm ‘Klaus’, in the western Mediterranean; (iv) December 2010 in the eastern Mediterranean; and (v) October 2011 in the central‐northern Mediterranean. European Centre for Medium‐range Weather Forecasts (ECMWF) reanalyses and 7 km resolution regional model simulations (COSMO) are analysed for each event. A Lagrangian viewpoint is employed to focus on interacting mechanisms that contribute to the joint impact on different spatial and temporal scales. In all cases, widespread strong wind gusts occur in the southwestern parts of the cyclone, while the precipitation field has localized peaks, with variable distribution in the central, southern, eastern and northern parts of the cyclone. Convective precipitation, significant in the cases in 2007, 2010 and 2011, is limited to the southern areas. In all cases, non‐convective precipitation is associated with ascent in a warm conveyor belt. Intense gusts are found within unstable air, below a low tropopause in a region with strong vertical wind shear, favouring downward momentum flux by turbulent mixing. Strongly descending dry intrusions are located coherently to the south and west of strong gusts. Much variability exists with regard to the emergence of convection, where strong winds and convective precipitation co‐occur: In the 2007 case, the dry intrusion is central in producing shallow convection in the cold frontal region. In the 2010 and 2011 cases, convective activity at high topography and in coastal regions leads to co‐location of both types of impact.

Heavy rainfall in Mediterranean cyclones. Part I: contribution of deep convection and warm conveyor belt

“…Then, from -6h to 0h, when most rainfall is produced, the WCB contributes about 50%, while DC contributes about 15 to 20%. Such strong contribution of WCBs to cyclone rainfall is consistent with the climatological results of Pfahl et al (2014) and with the five cyclone case analyses in Raveh and Wernli (2016). In cyclones producing low rainfall, the contribution of WCBs (Fig.…”

Moisture transport by tropical plumes over the Middle East: a 30‐year climatology

“…For the purposes of this study, the 'target area' is defined as the domain bounded within the coordinates of 23 • N, 31 • N, 36 • E, 44 • E. The choice of this domain is guided by several main considerations. The northern edge of the study region was limited to 31 • N in order to minimize the potential effect of moisture supplied from Mediterranean sources, which might add to the moisture conveyed by TPs (Raveh- Rubin and Wernli, 2016). The southern border of the domain was set at 23 • N to ensure that only cloud bands crossing the tropical belt are analysed.…”

An event synchronization method to link heavy rainfall events and large‐scale atmospheric circulation features

“…However, IVT alone appears not sufficient to identify with reasonable accuracy the large‐scale atmospheric circulation features driving the occurrence of heavy rainfall in a certain area, because the occurrence of heavy precipitation is also affected by the source and direction of the humidity transport (Pinto et al, ; Winschall et al, ; Raveh‐Rubin and Wernli, , ). In particular, Lavers and Villarini () suggest to use zonal and meridional wind at 850 hPa, or pressure surface at 850 hPa level, as further predictors beyond IVT.…”