Analysis of conveyor belts in winter Mediterranean cyclones

Ziv, Baruch; Saaroni, Hadas; Romem, M.; Heifetz, Eyal; Harnik, Nili; Baharad, Anat

doi:10.1007/s00704-009-0150-9

Cited by 48 publications

(47 citation statements)

References 35 publications

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“…All the three anomaly Z500 EM-patterns agree with the rainfall mechanisms proposed by Eshel and Farrell (2000) and Ziv et al (2010). On the right side of an anomalous low centre (in an equivalent barotropic context), southwesterly winds bring warm air towards the EM, causing vertical motion anomalies.…”

Section: Resultssupporting

confidence: 86%

“…Moreover, non-significant correlation between precipitation and moisture flux divergence (Jin and Zangvil, 2009) enhances the important role of vertical moisture fluxes from the warm Mediterranean Sea combined with the moisture transport from the western part of the Basin (e.g., Trigo et al, 2006). The role of the Mediterranean Sea is also evident in the Conveyor Belt Model of Ziv et al (2010) for the Mediterranean cyclones, where the warm belt plays a minor role (as a source of moisture) in contrast to its role in extratropical cyclones.…”

Section: Resultsmentioning

confidence: 99%

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Characterisation of extreme winter precipitation in Mediterranean coastal sites and associated anomalous atmospheric circulation patterns

Toreti

Xoplaki

Maraun

et al. 2010

Nat. Hazards Earth Syst. Sci.

160

135

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Abstract.We present an analysis of daily extreme precipitation events for the extended winter season (OctoberMarch) at 20 Mediterranean coastal sites covering the period . The heavy tailed behaviour of precipitation extremes and estimated return levels, including associated uncertainties, are derived applying a procedure based on the Generalized Pareto Distribution, in combination with recently developed methods. Precipitation extremes have an important contribution to make seasonal totals (approximately 60% for all series). Three stations (one in the western Mediterranean and the others in the eastern basin) have a 5-year return level above 100 mm, while the lowest value (estimated for two Italian series) is equal to 58 mm. As for the 50-year return level, an Italian station (Genoa) has the highest value of 264 mm, while the other values range from 82 to 200 mm. Furthermore, six series (from stations located in France, Italy, Greece, and Cyprus) show a significant negative tendency in the probability of observing an extreme event. The relationship between extreme precipitation events and the large scale atmospheric circulation at the upper, mid and low troposphere is investigated by using NCEP/NCAR reanalysis data. A 2-step classification procedure identifies three significant anomaly patterns both for the western-central and eastern part of the Mediterranean basin. In the western Mediterranean, the anomalous southwesterly surface to mid-tropospheric flow is connected with enhanced Correspondence to: A. Toreti (toreti@giub.unibe.ch) moisture transport from the Atlantic. During ≥5-year return level events, the subtropical jet stream axis is aligned with the African coastline and interacts with the eddy-driven jet stream. This is connected with enhanced large scale ascending motions, instability and leads to the development of severe precipitation events. For the eastern Mediterranean extreme precipitation events, the identified anomaly patterns suggest warm air advection connected with anomalous ascent motions and an increase of the low-to mid-tropospheric moisture. Furthermore, the jet stream position (during ≥5-year return level events) supports the eastern basin being in a divergence area, where ascent motions are favoured. Our results contribute to an improved understanding of daily precipitation extremes in the cold season and associated large scale atmospheric features.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Characterisation of extreme winter precipitation in Mediterranean coastal sites and associated anomalous atmospheric circulation patterns

Toreti

Xoplaki

Maraun

et al. 2010

Nat. Hazards Earth Syst. Sci.

160

135

View full text Add to dashboard Cite

show abstract

“…In this approximation, the flow is assumed adiabatic, D t θ = 0, with the thermal vertical advection in balance with the horizontal thermal advection and with the temperature tendency neglected. While the sign of the advections is correct in this approximation, the intensity of the advections is underestimated by this approximation when the development of the perturbations is strengthened by the diabatic interaction between the cold air masses and the warmer Mediterranean Sea (Ziv et al, 2010). In the upper troposphere, the horizontal wind shear in the exit region of the Atlantic jet and in the entrance region of the African jet is very large (Fig.…”

Section: Cross-jet Circulationsmentioning

confidence: 94%

Jetstream and rainfall distribution in the Mediterranean region

Gaetani

Baldi

Dalu

et al. 2011

Nat. Hazards Earth Syst. Sci.

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“…WCBs in this region occur most frequently during winter, and their ascent typically starts in the western North Atlantic. However, WCBs can originate over the entire North Atlantic and the Mediterranean (see also Ziv et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Airborne lidar observations in the inflow region of a warm conveyor belt

Schäfler

Dörnbrack

Wernli

et al. 2011

Quart J Royal Meteoro Soc

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). It is noteworthy that this substantial bias occurs in a potentially dynamically highly relevant air mass that will be subsequently lifted within a WCB to the upper troposphere. A Lagrangian moisture source diagnostic reveals that these large moisture deviations occur within air masses that, according to the ECMWF analyses, are coherently transported from the western Mediterranean towards Spain and experience intense moisture uptake over the Ebro valley. It is suggested that inaccuracies in surface evapotranspiration, horizontal moisture advection, and turbulent vertical transport of moisture in the atmospheric boundary layer potentially contribute to the erroneous lowtropospheric humidity in the inflow region of this particular summertime WCB over Spain in the ECMWF analyses.

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Analysis of conveyor belts in winter Mediterranean cyclones

Cited by 48 publications

References 35 publications

Characterisation of extreme winter precipitation in Mediterranean coastal sites and associated anomalous atmospheric circulation patterns

Characterisation of extreme winter precipitation in Mediterranean coastal sites and associated anomalous atmospheric circulation patterns

Jetstream and rainfall distribution in the Mediterranean region

Airborne lidar observations in the inflow region of a warm conveyor belt

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