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

Raveh‐Rubin, Shira; Flaounas, Emmanouil

doi:10.1002/asl.745

Cited by 41 publications

(39 citation statements)

References 36 publications

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“…Medicanes have drawn the attention of the scientific community with a range of studies focusing on their genesis (Emanuel, 2005; Chaboureau et al ., 2012; Raveh‐Rubin and Flaounas, 2017) and their evolution (Pytharoulis et al ., 2000; Claud et al ., 2010; Flaounas et al ., 2015). Concerning the last, many analyse the air–sea interactions and their impact on the evolution of the systems (Emanuel, 2005; Fita et al ., 2007; Miglietta et al ., 2011; Tous et al ., 2013; Akhtar et al ., 2014; Pytharoulis et al ., 2018; Stathopoulos et al ., 2020a).…”

Section: Introductionmentioning

confidence: 99%

Wind and wave extremes associated with tropical‐like cyclones in the Mediterranean basin

Πατλάκας

Stathopoulos

Tsalis

et al. 2020

Intl Journal of Climatology

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The Mediterranean Sea is a basin with intense cyclonic activity. The multidimensional impact of such weather events on human life enhances the need and highlights the importance for further research. In this framework, there is a great interest for the development, evolution and impacts of tropical-like cyclones in the basin (medicanes). Besides their scientifically appealing features, their extremity and presence in a populated region with intense coastal activities can lead to social, natural and financial implications. The purpose of this work is the characterization of the risk exposed areas by this type of cyclones alongside their intensity and recurrence interval in terms of wind and wave parameters. In order to consider more than the strict and direct effects of

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Section: Introductionmentioning

confidence: 99%

Wind and wave extremes associated with tropical‐like cyclones in the Mediterranean basin

Πατλάκας

Stathopoulos

Tsalis

et al. 2020

Intl Journal of Climatology

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“…Concerning the most intense Mediterranean cyclones, there is a general consensus that Mediterranean cyclogenesis is provoked by intruding upper-tropospheric systems that trigger baroclinic instability (Fita et al 2006;Kouroutzoglou et al 2011;Claud et al 2010;Flaounas et al 2015). Such systems typically correspond to potential vorticity (PV) streamers, equivalent to southern deviations of the Polar Jet that are a direct result of wave breaking over the Atlantic Ocean (Raveh-Rubin and Flaounas, 2017). After cyclogenesis takes place, baroclinic forcing may further intensify surface cyclones (e.g.…”

Section: Introductionmentioning

confidence: 99%

A process-based anatomy of Mediterranean cyclones: From baroclinic lows to tropical-like systems

Flaounas¹,

Gray²,

Teubler³

2020

Preprint

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Abstract. In this study, we address the question of the atmospheric processes that turn Mediterranean cyclones into severe storms. Our approach applies on-line potential vorticity (PV) budget diagnostics and piecewise PV inversion to WRF model simulations of the mature stage of 100 intense Mediterranean cyclones. We quantify the relative contributions of different processes to cyclone development and therefore deliver, for the first time, a comprehensive insight into the variety of cyclonic systems that develop in the Mediterranean from the perspective of cyclone dynamics. In particular, we show that all 100 cyclones are systematically influenced by two main PV anomalies: a major anomaly in the upper troposphere, related to the baroclinic forcing of cyclone development, and a minor anomaly in the lower troposphere, related to diabatic processes and momentum forcing of wind. Among the diabatic processes, latent heat is shown to act as the main PV source (reinforcing cyclones), being partly balanced by PV sinks of temperature diffusion and radiative cooling (weakening cyclones). Momentum forcing is shown to have an ambiguous feedback, able to reinforce and weaken cyclones while in certain cases playing an important role in cyclone development. Piecewise PV inversion shows that most cyclones develop due to the combined effect of both baroclinic and diabatic forcing, i.e. due to both PV anomalies. However, the stronger the baroclinic forcing, the less a cyclone is found to develop due to diabatic processes. Several pairs of exemplary cases are used to illustrate the variety of contributions of atmospheric processes to the development of Mediterranean cyclones: (i) cases where both baroclinic and diabatic processes contribute to cyclone development; (ii) cases that mainly developed due to latent-heat release; (iii) cases developing in the wake of the Alps; and (iv) two unusual cases, one where momentum forcing dominates cyclone development and the other presenting a dual surface pressure centre. Finally, we focus on ten medicane cases (i.e. tropical-like cyclones). In contrast to their tropical counterparts – but in accordance with most intense Mediterranean cyclones – most medicanes are shown to develop under the influence of both baroclinic and diabatic processes. In discussion of medicane driving processes, we highlight the need for a physical definition of these systems.

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“…12 in Thorncroft et al (1993). This process, through which cyclonically or anticyclonically breaking troughs and ridges displace the jet, is even able to excite positive or negative North Atlantic Oscillation events (Benedict et al, 2004;Franzke et al, 2004;Rivière and Orlanski, 2007). A traditional means for quantifying the influence of upper-level troughs and ridges on the jet strength and location is the E vector (Hoskins et al, 1983;Trenberth, 1986).…”

Section: Introductionmentioning

confidence: 99%

The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics

Schemm

Rüdisühli

Sprenger

2020

Weather Clim. Dynam.

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Abstract. A novel method is introduced to identify and track the life cycle of upper-level troughs and ridges. The aim is to close the existing gap between methods that detect the initiation phase of upper-level Rossby wave development and methods that detect Rossby wave breaking and decaying waves. The presented method quantifies the horizontal trough and ridge orientation and identifies the corresponding trough and ridge axes. These allow us to study the dynamics of pre- and post-trough–ridge regions separately. The method is based on the curvature of the geopotential height at a given isobaric surface and is computationally efficient. Spatiotemporal tracking allows us to quantify the maturity of troughs and ridges and could also be used to study the temporal evolution of the trough or ridge orientation. First, the algorithm is introduced in detail, and several illustrative applications – such as a downstream development from the North Atlantic into the Mediterranean – and seasonal climatologies are discussed. For example, the climatological trough and ridge orientations reveal strong zonal and meridional asymmetry: over land, most troughs and ridges are anticyclonically oriented, while they are cyclonically oriented over the main oceanic storm tracks; the cyclonic orientation increases toward the poles, while the anticyclonic orientation increases toward the Equator. Trough detection frequencies are climatologically high downstream of the Rocky Mountains and over East Asia and eastern Europe but are remarkably low downstream of Greenland. Furthermore, the detection frequencies of troughs are high at the end of the North Pacific storm track and at the end of the North Atlantic storm track over the British Isles. During El Niño-affected winters, troughs and ridges exhibit an anomalously strong cyclonic tilt over North America and the North Atlantic, in agreement with previous findings based on traditional variance-based diagnostics such as E vectors. During La Niña, the situation is essentially reversed. The orientation of troughs and ridges also depends on the jet position. For example, during midwinter over the Pacific, when the subtropical jet is strongest and located farthest equatorward, cyclonically oriented troughs and ridges dominate the climatology. Finally, the identified troughs and ridges are used as starting points for 24 h backward parcel trajectories, and a discussion of the distribution of pressure, potential temperature and potential vorticity changes along the trajectories is provided to give insight into the three-dimensional nature of troughs and ridges.

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

Abstract: Breaking of atmospheric Rossby waves has been previously shown to lead to intense Mediterranean cyclones, one of the most prominent environmental risks in the region. Wave breaking may be enhanced by warm conveyor belts (

Cited by 41 publications

References 36 publications

Wind and wave extremes associated with tropical‐like cyclones in the Mediterranean basin

Wind and wave extremes associated with tropical‐like cyclones in the Mediterranean basin

A process-based anatomy of Mediterranean cyclones: From baroclinic lows to tropical-like systems

The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics

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