HR: 13:55h
AN: H53J-02 INVITED     [Abstracts]
TI: Patterns and mechanisms of orographic precipitation in the Olympic Mountains, Washington State
AU: * Durran, D R
EM: durrand@atmos.washington.edu
AF: Department of Atmospheric Sciences, ATG, University of Washington, Seattle, WA 98195 United States
AU: Minder, J U
EM: juminder@atmos.washington.edu
AF: Department of Atmospheric Sciences, ATG, University of Washington, Seattle, WA 98195 United States
AU: Anders, A M
EM: andersa@u.washington.edu
AF: Department of Earth and Space Sciences, Condon Hall, University of Washington, Seattle, WA 98195 United States
AU: Roe, G H
EM: gerard@ess.washington.edu
AF: Department of Earth and Space Sciences, Condon Hall, University of Washington, Seattle, WA 98195 United States
AB: Although the existence of rain shadows and the processes responsible for them are well established, the relationship between precipitation and orography on smaller scales is much less certain, and has received relatively little attention. Yet it is precisely at these spatial scales that precipitation has some of its largest impacts on the landscape. For the Olympics in Washington State, a typical midlatitude mountain range, we use the unique combination of six years of operational output from a high-resolution state-of-the-art mesoscale forecast model, and a dense network of precipitation gauges specifically sited to sample across large precipitation gradients. With only a few exceptions, we find a remarkable and persistent 1.5- to 2-fold enhancement of precipitation on the major ridges compared to the major valleys, despite variability in wind speed and direction, and the temperature and humidity of the incoming air. This is true for big storms, medium storms, rain and snow, as well as in the climatological average. The underlying mechanisms giving rise to this robust pattern are investigated in detail with specific case studies, including both stable and unstable flow regimes. The results are compared with dynamical and microphysical theories of orographic precipitation.
DE: 1840 Hydrometeorology
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1854 Precipitation (3354)
DE: 3329 Mesoscale meteorology
SC: Hydrology [H]
MN: Fall Meeting 2005