Wednesday, 7 August 2013: 9:30 AM
Multnomah (DoubleTree by Hilton Portland)
During the warm season, strong surface heating and land-water contrasts combine with the complex topography of the Pacific Northwest to create diurnal circulations that affect not only wind speed and direction, but also cloudiness, temperature, and moisture. Though observational studies and modeling case studies have described many of these circulations, advances in high-resolution numerical modeling allow for a more comprehensive, three-dimensional examination of these important features. For several years now, the University Of Washington Department Of Atmospheric Sciences has been running the Weather Research and Forecasting model (WRF) at 36, 12, and 4 km resolution. Composites from real-time WRF model output at 12 and 4 km were created to analyze the various diurnal circulations that occur over the region. Though these composites provide important information on the dominant summertime diurnal wind circulations, compositing smooths these features. Summertime composites of GFS model output were used to initialize and provide boundary conditions to a WRF model run. This run shows substantially sharper wind features compared to the WRF real-time composites, and better reflects what is expected on a typical summer day. In this talk, the results of this run will be used to describe the diurnal, three-dimensional circulations over the region, as well as their implications for clouds, precipitation, and other major variables.
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