Heavy rainfall in Mediterranean cyclones, Part II: Water budget, precipitation efficiency and remote water sources

Flaounas, Emmanouil; Fita, L.; Lagouvardos, Konstantinos; Kotroni, Vassiliki

doi:10.1007/s00382-019-04639-x

Cited by 28 publications

(60 citation statements)

References 41 publications

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“…Fita and Flaounas, 2018), one remarkable characteristic of many medicanes is the transition of the cyclonic system transitions from extratropical to tropical (e.g. Gaertner et al, 2018). Hart (2003) proposes an objective measurement of cyclone phase space defined as…”

Section: Estimation Of the Cyclone Phase Space (Cps)mentioning

confidence: 99%

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Modelling a tropical-like cyclone in the Mediterranean Sea under present and warmer climate

Koseki

Mooney

Cabos

et al. 2021

Nat. Hazards Earth Syst. Sci.

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Abstract. This study focuses on a single Mediterranean hurricane (hereafter medicane), to investigate its response to global warming during the middle of the 21st century and assesses the effects of a warmer ocean and a warmer atmosphere on its development. Our investigation uses the state-of-the-art regional climate model WRF to produce the six-member, multi-physics ensembles. Results show that our model setup simulates a realistic cyclone track and the transition from an initial disturbance to a tropical-like cyclone with a deep warm core. However, the simulated transition occurs earlier than for the observed medicane. The response of the medicane to future climate change is investigated with a pseudo global warming (PGW) approach. This is the first application of the PGW framework to medicanes. The PGW approach adds a climate change delta (defined as difference between future and present climate) to WRF's boundary conditions which is obtained for all prognostic variables using the mean change in an ensemble of CMIP5 simulations. A PGW simulation where the climate change delta is added to all prognostic variables (PGWALL) shows that most of the medicane characteristics moderately intensify, e.g. surface wind speed, uptake of water vapour, and precipitation. However, the minimum sea level pressure (SLP) is almost identical to that under present climate conditions. Two additional PGW simulations were undertaken; One simulation adds the projected change in sea surface and skin temperature only (PGWSST) while the second simulation adds the PGW changes to only atmospheric variables (PGWATMS); i.e. we use present-day sea surface temperatures. These simulations show opposing responses of the medicane. In PGWSST, the medicane is more intense than PGWALL as indicated by lower SLP values, the stronger surface wind, and the more intense evaporation and precipitation. In contrast, the medicane in PGWATMS still transitions into a tropical-like cyclone with a deep warm core, but the PGWATMS medicane weakens considerably (SLP, surface wind, and rainfall decrease). This difference can be explained by an increase in water vapour driven by the warmer ocean surface (favourable for cumulus convection). The warmer and drier atmosphere in PGWATMS tends to inhibit condensation (unfavourable for cumulus convection). The warmer ocean and warmer atmosphere have counteracting effects which leads to only a modest enhancement of the medicane by global warming. The novel approach in this study provides new insights into the different roles of warming of the ocean and atmosphere in medicane development.

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Section: Estimation Of the Cyclone Phase Space (Cps)mentioning

confidence: 99%

“…the cyclone core and the associated rain bands. Consequently, the intensity of medicanes is underestimated in most coupled regional models (Gaertner et al, 2018). Therefore, it is most likely that CGCMs also underestimate future changes in medicanes.…”

Section: Introductionmentioning

confidence: 99%

Modelling a tropical-like cyclone in the Mediterranean Sea under present and warmer climate

Koseki

Mooney

Cabos

et al. 2021

Nat. Hazards Earth Syst. Sci.

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“…However, Mediterranean cyclones are also affected by the complex geography of the region. For instance, the relatively small size of the Mediterranean Sea and the arid areas of North Africa have an indirect effect on cyclones by limiting their supply of water vapour (Flaounas et al, 2019). On the other hand, the high mountains that surround the Mediterranean basin have a direct effect on cyclones by interacting with the air flow and triggering PV banners, i.e.…”

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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“…Additionally, they can provide 3D fields of otherwise unmeasurable meteorological variables, thus contributing to our understanding of the dynamics of HPEs. Studies based on high-resolution NWP models commonly focus on specific cases, with only a few also examining the climatology of model results, either for determining the atmospheric conditions that trigger HPEs, or understanding the overall rainfall pattern in comparison with observational records (e.g., Flaounas et al, 2019;Kendon et al, 2014;Khodayar et al, 2018). Commonly, climate change studies based on high-resolution NWP models characterise the expected changes in precipitation focusing on rainfall intensity or frequency, or some derived index (e.g., Ban et al, 2014;Hochman et al, 2018a;Schär et al, 2016;Westra et al, 2014).…”

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confidence: 99%

Characterising patterns of heavy precipitation events in the eastern Mediterranean using a weather radar and convection-permitting WRF simulations

Armon

Marra

Enzel

et al. 2019

Preprint

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Abstract. Heavy precipitation events (HPEs) can lead to natural hazards (floods, debris flows) and contribute to water resources. Rainfall patterns govern HPEs effects. Thus, a correct characterisation and prediction of rainfall patterns is crucial for coping with HPEs. Information from rain gauges is generally limited due to the sparseness of the networks, especially in presence of sharp climatic gradients. Forecasting HPEs depends on the ability of weather models to generate credible rainfall patterns. This paper characterises rainfall patterns during HPEs based on high-resolution weather radar data and evaluates the performance of a high-resolution, convection-permitting, Weather Research and Forecasting (WRF) model in simulating these patterns. We identified 41 HPEs in the eastern Mediterranean from a 24-year radar record using local thresholds based on quantiles for different durations, and we ran model simulations of these events. For most durations, HPEs near the coastline are characterised by the highest rain intensities, however, for short durations, the highest rain intensities characterise the inland desert. During the rainy season, the centre-of-mass of the rain field progresses from the sea inland. Rainfall during HPEs is highly localised both in space (

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Heavy rainfall in Mediterranean cyclones, Part II: Water budget, precipitation efficiency and remote water sources

Cited by 28 publications

References 41 publications

Modelling a tropical-like cyclone in the Mediterranean Sea under present and warmer climate

Modelling a tropical-like cyclone in the Mediterranean Sea under present and warmer climate

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

Characterising patterns of heavy precipitation events in the eastern Mediterranean using a weather radar and convection-permitting WRF simulations

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