Research Article

Evolution and structure of a cold front in an Alpine valley as revealed by a Doppler lidar

  1. Alexander Gohm1,*,
  2. Georg J. Mayr1,
  3. Lisa S. Darby2,†,
  4. Robert M. Banta2,†

Article first published online: 21 APR 2010

DOI: 10.1002/qj.609

Issue

Quarterly Journal of the Royal Meteorological Society

Quarterly Journal of the Royal Meteorological Society

Volume 136, Issue 649, pages 962–977, April 2010 Part B

Additional Information

How to Cite

Gohm, A., Mayr, G. J., Darby, L. S. and Banta, R. M. (2010), Evolution and structure of a cold front in an Alpine valley as revealed by a Doppler lidar. Q.J.R. Meteorol. Soc., 136: 962–977. doi: 10.1002/qj.609

Author Information

  1. 1

    University of Innsbruck, Austria

  2. 2

    NOAA, Earth System Research Laboratory, USA

  1. †

    The contribution of Lisa S. Darby and Robert M. Banta to this article was prepared as part of their official duties as United States Federal Government employees.

*Institute of Meteorology and Geophysics, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria.

  1. †

    The contribution of Lisa S. Darby and Robert M. Banta to this article was prepared as part of their official duties as United States Federal Government employees.

Publication History

  1. Issue published online: 14 JUN 2010
  2. Article first published online: 21 APR 2010
  3. Manuscript Accepted: 22 FEB 2010
  4. Manuscript Revised: 13 JAN 2010
  5. Manuscript Received: 23 OCT 2009

Funded by

  • Austrian Science Fund (FWF). Grant Numbers: P13489, P15077

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Keywords:

  • density current;
  • Mesoscale Alpine Programme;
  • south foehn

Abstract

The propagation of a cold front and its interaction with foehn winds is investigated in an Alpine valley, based on observations collected during the field campaign of the Mesoscale Alpine Programme (MAP) on 6 November 1999. The key instrument of this study is a Doppler lidar that had been operated in the Wipp Valley (Austria). The cold front approached the European Alps from the northwest, became distorted at the mountain barrier and entered the east– west aligned Inn Valley near the town of Innsbruck primarily via two passes. It continued to propagate towards Innsbruck from both valley directions as two separate fronts that eventually collided east of Innsbruck after part of the cold air had entered the adjacent north– south aligned Wipp Valley.

A synthesis of Doppler lidar measurements with conventional meteorological data, including automatic weather stations and radiosondes, leads to the conclusion that the cold front in the Wipp Valley was an atmospheric density current characterized by an elevated head, a front-relative feeder flow and a typical propagation speed of 7 m s−1. The foehn flow on top of the density current caused strong wind shear and triggered shear-flow instability that led to the formation of a turbulent wake behind the head. As the density current propagated towards the Brenner Pass, it slowed down. The shape of the frontal surface varied in time. Its inclination of about 10°– 20° is steeper than previously reported for the Inn Valley but is consistent with other observations of atmospheric density currents. Copyright © 2010 Royal Meteorological Society

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