Repository: Freie Universit├Ąt Berlin, Math Department

A Characterization of the Meteorological Environment Associated with the Tropical Transition of a Medicane in the Western Mediterranean Sea

Mazza, E. and Ulbrich, U. and Klein, R. (2015) A Characterization of the Meteorological Environment Associated with the Tropical Transition of a Medicane in the Western Mediterranean Sea. SFB1114-Preprint . (Submitted)

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Abstract

In order to identify the distinctive characteristics of the meteorological environment supporting the tropical transition of the October 1996 medicane in the western Mediterranean, its spatial and temporal evolution is investigated on the basis of a 50-member ensemble of reanalyses-driven RCM atmospheric simulations. As the cyclones undergo a warm seclusion-like process, the initial thermal asymmetries and vertical tilt are reduced while a warm core builds upward from the lower troposphere. A comparison of the composite environments of transitioning and non-transitioning storms reveals that the former feature enhanced convection and higher mid-to-low tropospheric relative humidity, resulting in a stronger diabatic heat release aloft, along with increased upper-level wind divergence. At the time of transition, vertical wind shear is not significantly different, as it is reduced in both composites below the thresholds typically found for tropical cyclogeneses. Upper-level wind divergence and wind shear are positively correlated, hence the additional forcing on convection due to stronger divergence could partially counteract the detrimental effects of larger shear. In the transitioning cyclones, surface sensible and latent heat fluxes become significantly larger only in proximity of the transition. Finally, the upper-tropospheric warm core strength exhibits a strong, negative linear correlation with wind shear. Moderately positive correlation coefficients are instead found for latent and sensible heat fluxes while upper-level divergence and mid-to-low tropospheric relative humidity show small and negative correlations.

Item Type:Article
Additional Information:accepted and to appear in Monthly Weather Review
Subjects:Mathematical and Computer Sciences > Mathematics > Applied Mathematics
Divisions:Department of Mathematics and Computer Science > Institute of Mathematics > Geophysical Fluid Dynamics Group
ID Code:1761
Deposited By: Ulrike Eickers
Deposited On:04 Dec 2015 08:55
Last Modified:14 Aug 2017 12:02

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