Advertisement

Theoretical and Applied Climatology

, Volume 74, Issue 1–2, pp 53–67 | Cite as

Regional effects of large-scale extreme wind events over orographically structured terrain

  • N. Kalthoff
  • I. Bischoff-Gauß
  • F. Fiedler

Summary

¶Above orographically structured terrain considerable differences of the regional wind field may be identified during large-scale extreme wind events. So far, these regional differences could not be resolved by climate models. To determine the relationships between large-scale atmospheric conditions, the influence of orography, and the regional wind field, data measured in the upper Rhine valley within the framework of the REKLIP Regional Climate Project were analyzed and calculations were made using the KAMM mesoscale model. In the area of the upper Rhine valley, ratios of the wind velocity in the Rhine valley at 10 m above ground level, νval, and the large-scale flow velocity, νlar, are between νvallar ≈ 0.1 and νvallar ≈ 1. The νvallar ratio exhibits a strong dependence on thermal stratification, δ, and decreases from νvallar ≈ 1 at δ = 0 K m−1 to νvallar ≈ 0.2 at δ = 0.0075 K m−1. In areas, where the lateral mountainous border of the Rhine valley is interrupted, the νvallar ratio increases again with increasing stability or decreasing Froude number. This is obviously due to flow around the Black Forest under stable stratification. It is demonstrated by model calculations that a complex wind field develops in the Rhine valley at small Froude numbers (Fr < 1) irrespective of the direction of large-scale flow. The νvallar ratio is characterized by small values in the direct lee side (νvallar ≈ 0.2) and high values on the windward side of the lateral mountainous border of the Rhine valley (νvallar ≈ 0.8).

Keywords

Stratification Regional Climate Wind Velocity Regional Effect Atmospheric Condition 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag/Wien 2002

Authors and Affiliations

  • N. Kalthoff
    • 1
  • I. Bischoff-Gauß
    • 2
  • F. Fiedler
    • 1
  1. 1.Institut für Meteorologie und Klimaforschung, Universität Karlsruhe/Forschungszentrum Karlsruhe, Karlsruhe, GermanyDE
  2. 2.Hauptabteilung Informations- und Kommunikationstechnik, Forschungszentrum Karlsruhe, Karlsruhe, GermanyDE

Personalised recommendations