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Reconstruction of near-surface tornado wind fields from forest damage

Beck, Veronika and Dotzek, Nikolai (2010) Reconstruction of near-surface tornado wind fields from forest damage. Journal of Applied Meteorology and Climatology, 49 (7), pp. 1517-1537. American Meteorlogical Society. DOI: 10.1175/2010JAMC2254.1.

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Tornado intensity is usually inferred from the damage produced. To foster postevent tornado intensity assessments, the authors present a model to reconstruct near-surface wind fields from forest damage patterns. By comparing the structure of observed and simulated damage patterns, essential parameters to describe a tornado near-surface wind field are derived, such as the ratio Gmax between circular and translational velocity, and the deflection angle a between peak wind and pressure gradient. The model consists of a wind field module following the Letzmann analytical tornado model and a tree module based on the mechanistic HWIND tree model to assess tree breakage. Using this method, the velocity components of the near-surface wind field, the track of the tornado center, and the spatial distribution of the Fujita scale along and across the damage path can be assessed. Necessary requirements to apply the model are knowledge of the tornado translation speed (e.g., from radar observations) and a detailed analysis of the forest damage patterns. One of the key findings of this analysis is that the maximum intensity of the tornado is determinable with an uncertainty of only (Gmax 1 1) times the variability of the usually well-known tornado translation speed. Further, if Letzmann�s model is applied and the translation speed of the tornado is known, the detailed tree model is unnecessary and could be replaced by an average critical velocity for stem breakage ycrit independent of the tree species. Under this framework, the F3 and F2 ratings of the tornadoes in Milosovice, Czech Republic, on 30 May 2001 and Castellcir, Spain, on 18 October 2006, respectively, could be verified. For the Milosovice event, the uncertainty in peak intensity was only 66.0 m s21. Additional information about the structure of the near-surface wind field in the tornado and several secondary vortices was also gained. Further, this model allows for distinguishing downburst damage patterns from those of tornadoes.

Document Type:Article
Title:Reconstruction of near-surface tornado wind fields from forest damage
AuthorsInstitution or Email of Authors
Dotzek, NikolaiUNSPECIFIED
Journal or Publication Title:Journal of Applied Meteorology and Climatology
Refereed publication:Yes
In ISI Web of Science:Yes
Page Range:pp. 1517-1537
Publisher:American Meteorlogical Society
Keywords:assessment, tornado intensity, forest damage
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Dr.rer.nat. Michael Ponater
Deposited On:07 Sep 2010 08:22
Last Modified:12 Dec 2013 21:01

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