A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains

The initiation of a deep and severe impact Mediterranean cyclone in the lee of the Atlas Mountains is investigated by a series of numerical experiments using the MM5 forecast model. The roles of orography, surface sensible heat flux and upper-level potential vorticity anomaly are identified using th...

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Main Authors: Kristian Horvath, Lluis Fita, Romualdo Romero, Branka Ivancan-Picek
Format: Article
Language:English
Published: Borntraeger 2006-04-01
Series:Meteorologische Zeitschrift
Online Access:http://dx.doi.org/10.1127/0941-2948/2006/0113
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author Kristian Horvath
Lluis Fita
Romualdo Romero
Branka Ivancan-Picek
author_facet Kristian Horvath
Lluis Fita
Romualdo Romero
Branka Ivancan-Picek
author_sort Kristian Horvath
collection DOAJ
description The initiation of a deep and severe impact Mediterranean cyclone in the lee of the Atlas Mountains is investigated by a series of numerical experiments using the MM5 forecast model. The roles of orography, surface sensible heat flux and upper-level potential vorticity anomaly are identified using the factor separation method. In addition, a sensitivity experiment addressing the role of a thermal anomaly in the lee of the Atlas is performed. The results of model simulations show that orography blocking is responsible for the generation of a low-level shallow vortex in the first phase of the lee development. An upper-level potential vorticity anomaly is the principal ingredient of this event, responsible for a dominant deepening effect in the later stage of lee formation. The analysis of the cyclone paths shows that orography tends to keep the cyclone stationary, while upper-level dynamical factors prove crucial for the advection of the system to the Mediterranean Sea. The most noteworthy influence of surface sensible heat flux is identified as an afternoon destruction of the surface baroclinic zone and the associated weaker cyclogenesis. Furthermore, it is shown that the thermal anomaly in the lee of the Atlas builds up rather quickly and tends to be responsible for the cyclone initiation positioning in the mountain lee.
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spelling doaj.art-4da7238e8c614066b06538b52de617a32024-02-08T08:48:58ZengBorntraegerMeteorologische Zeitschrift0941-29482006-04-0115213314610.1127/0941-2948/2006/011354954A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas MountainsKristian HorvathLluis FitaRomualdo RomeroBranka Ivancan-PicekThe initiation of a deep and severe impact Mediterranean cyclone in the lee of the Atlas Mountains is investigated by a series of numerical experiments using the MM5 forecast model. The roles of orography, surface sensible heat flux and upper-level potential vorticity anomaly are identified using the factor separation method. In addition, a sensitivity experiment addressing the role of a thermal anomaly in the lee of the Atlas is performed. The results of model simulations show that orography blocking is responsible for the generation of a low-level shallow vortex in the first phase of the lee development. An upper-level potential vorticity anomaly is the principal ingredient of this event, responsible for a dominant deepening effect in the later stage of lee formation. The analysis of the cyclone paths shows that orography tends to keep the cyclone stationary, while upper-level dynamical factors prove crucial for the advection of the system to the Mediterranean Sea. The most noteworthy influence of surface sensible heat flux is identified as an afternoon destruction of the surface baroclinic zone and the associated weaker cyclogenesis. Furthermore, it is shown that the thermal anomaly in the lee of the Atlas builds up rather quickly and tends to be responsible for the cyclone initiation positioning in the mountain lee.http://dx.doi.org/10.1127/0941-2948/2006/0113
spellingShingle Kristian Horvath
Lluis Fita
Romualdo Romero
Branka Ivancan-Picek
A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains
Meteorologische Zeitschrift
title A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains
title_full A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains
title_fullStr A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains
title_full_unstemmed A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains
title_short A numerical study of the first phase of a deep Mediterranean cyclone: Cyclogenesis in the lee of the Atlas Mountains
title_sort numerical study of the first phase of a deep mediterranean cyclone cyclogenesis in the lee of the atlas mountains
url http://dx.doi.org/10.1127/0941-2948/2006/0113
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