The dynamical structure of intense Mediterranean cyclones

Abstract

International audienceThis paper presents and analyzes the three-dimensional dynamical structure of intense Mediterranean cyclones. The analysis is based on a composite approach of the 200 most intense cyclones during the period 1989-2008 that have been identified and tracked using the output of a coupled ocean-atmosphere regional simulation with 20 km horizontal grid spacing and 3-hourly output. It is shown that the most intense Mediterranean cyclones have a common baroclinic life cycle with a potential vorticity (PV) streamer associated with an upper-level cyclonic Rossby wave breaking, which precedes cyclogenesis in the region and triggers baroclinic instability. It is argued that this common baroclinic life cycle is due to the strongly horizontally sheared environment in the Mediterranean basin, on the poleward flank of the quasi-persistent subtropical jet. The composite life cycle of the cyclones is further analyzed considering the evolution of key atmospheric elements as potential temperature and PV, as well as the cyclones' thermodynamic profiles and rainfall. It is shown that most intense Mediterranean cyclones are associated with warm conveyor belts and dry air intrusions, similar to those of other strong extratropical cyclones, but of rather small scale. Before cyclones reach their mature stage, the streamer's role is crucial to advect moist and warm air towards the cyclones center. These dynamical characteristics, typical for very intense extratropical cyclones in the main storm track regions, are also valid for these Mediterranean cases that have features that are visually similar to tropical cyclones

Assessment of an ensemble of ocean–atmosphere coupled and uncoupled regional climate models to reproduce the climatology of Mediterranean cyclones

“…Figure 3c shows the seasonal cycle of the 500 most intense cyclones in ERAI. All methods show a lower frequency of intense cyclones in summer and a higher one in spring and winter, in agreement with previous studies of intense Mediterranean cyclones (e.g., Campins et al 2011;Cavicchia et al 2014;Flaounas et al 2015b). …”

“…These cyclones have a strong impact on the Mediterranean climate, its variability and extremes (e.g., Trigo et al 2000;Lionello et al 2006;Gaertner et al 2007;Lionello and Giorgi 2007;Walsh et al 2014;Zappa et al 2015). Indeed, several studies showed the significant contribution of cyclones to the majority of rainfall and wind extremes (e.g., Jansà et al 2001;Nissen et al 2010;Reale and Lionello 2013;RavehRubin and Wernli 2015), to the formation of the most prominent high impact weather events (Llasat et al 2010), as well as to the modulation of the Mediterranean hydrological cycle (Romanski et al 2012;Flaounas et al 2015b).…”

Offshore wind climate analysis and variability in the Mediterranean Sea

“…The Mediterranean Sea is one of the most cyclogenetic areas in the world (Campins et al, 2011;Flaounas et al, 2015aFlaounas et al, , 2015b, where explosive cyclogenesis (Lagouvardos et al, 2007) and tropical-like cyclones also occur (Lagouvardos et al, 1999;Tous and Romero, 2013).…”

Impact of the internal variability on the cyclone tracks simulated by a regional climate model over the Med-CORDEX domain

“…The Mediterranean cyclones simulated by climate models have been already investigated in some studies as Trigo et al (2002), Lionello et al (2008), Flaounas et al (2013Flaounas et al ( , 2014. In their inter-comparison analysis, Flaounas et al (2016, this issue) already shows that ALADIN is able to simulate correctly some properties (location, intensity) of the Mediterranean cyclones.…”