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A numerical study of the effects of orography on supercells

Markowski, Paul M. and Dotzek, Nikolai (2011) A numerical study of the effects of orography on supercells. Atmospheric Research, 100, pp. 457-478. Elsevier. DOI: 10.1016/j.atmosres.2010.12.027.

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Official URL: http://bricker.met.psu.edu/~marko/pubs/2011/MD11ATMOSRES.pdf

Abstract

The effects of idealized two- and three-dimensional terrain on a cyclonically rotating supercell thunderstorm are studied with a numerical model. The airflow over the terrain produces horizontal heterogeneity in the characteristics of the soundings and hodographs, which, in horizontally homogeneous environments, are the primarily factors that influence storm structure and evolution. Indeed, many of the differences between control simulations that feature storms over flat terrain and simulations in which terrain variations are introduced (e.g., a hill, escarpment, and valley) can be ascribed to differences in the storm environments, especially the thermodynamic conditions (variations in convective inhibition and relative humidity have the biggest effect on the simulated storms), caused by the airflow over and/or around the terrain. Regions of downsloping winds tend to be regions of enhanced convective inhibition and reduced relative humidity. Accordingly, there is a tendency for the simulated supercells to weaken (in terms of the intensities of their updrafts and mesocyclones) in the lee of terrain features where downsloping is present. Though most aspects of convective storm dynamics are independent of the ground-relative winds and only depend on the storm-relative winds, the ground-relative wind profile is of leading-order importance in determining the impact of the underlying terrain on the storms that cross it; the ground-relative wind profile dictates where winds will blow upslope or downslope, which controls to a large extent the manner in which the environment is modified. When three-dimensional terrain is introduced (e.g., an isolated hill, a gap incised into a ridge), the resulting horizontal heterogeneity in the thermodynamic and vertical wind shear fields is considerably more complex than in the case of two-dimensional terrain (e.g., an infinitely long hill, valley, or escarpment). The effect of three-dimensional terrain on the storm environment can be further complicated by the generation of mesoscale vertical vorticity anomalies. In some cases, the interaction of supercells with preexisting lee vorticity anomalies can briefly enhance low-level rotation within the storm; however, the dominant role of three-dimensional terrain generally is its modification of soundings and hodographs, as is the case for two-dimensional terrain.

Document Type:Article
Title:A numerical study of the effects of orography on supercells
Authors:
AuthorsInstitution or Email of Authors
Markowski, Paul M.Pennsylvania State Univ., University Park, PA, USA
Dotzek, NikolaiUNSPECIFIED
Date:2011
Journal or Publication Title:Atmospheric Research
Refereed publication:Yes
In Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:100
DOI:10.1016/j.atmosres.2010.12.027
Page Range:pp. 457-478
Publisher:Elsevier
Status:Published
Keywords:Supercell Thunderstorm Mountains Mesocyclone
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Vorhaben Atmosphären- und Klimaforschung
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Dr.rer.nat. Michael Ponater
Deposited On:03 Nov 2011 15:06
Last Modified:12 Dec 2013 21:23

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