Two-Dimensional Idealized Simulations of the Impact of Multiple Windward Ridges on Orographic Precipitation

This paper presents two-dimensional (2D) idealized simulations at 1-km grid spacing using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) in order to illustrate how a series of ridges along a broad windward slope can impact...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 2008-02, Vol.65 (2), p.509-523
Main Author: COLLE, Brian A
Format: Article
Language:English
Subjects:
Atmospheric research
Case studies
Clouds
Earth, ocean, space
Exact sciences and technology
External geophysics
Freezing
Meteorology
Orographic precipitation
Physics of the high neutral atmosphere
Precipitation
Ridges
Synergistic effect
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Summary:This paper presents two-dimensional (2D) idealized simulations at 1-km grid spacing using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) in order to illustrate how a series of ridges along a broad windward slope can impact the precipitation distribution and simulated microphysics. The number of windward ridges for a 2000-m mountain of 50-km half-width is varied from 0 to 16 over a 150-km distance using different stratifications, freezing levels, uniform ambient flows, and ridge amplitudes. A few (200–400 m) windward ridges can enhance the precipitation locally over each ridge crest by a factor of 2–3. Meanwhile, a series of 8–16 ridges that are 200–400 m in height can increase the net precipitation averaged over the windward slope by 10%–35%. This average precipitation enhancement is maximized when the ridge spacing is relatively small (
ISSN:0022-4928
1520-0469
DOI:10.1175/2007jas2305.1