4.5 An urban mixed layer climatology for North America using the AERMET model

Tuesday, 21 June 2005: 3:45 PM
South Ballroom (Hilton DeSoto)
Matthew Simpson, North Carolina State Univ., Raleigh, NC; and S. Raman and A. H. Huber

Mixing height climatologies were developed for 21 urban areas in the United States and Canada using the American Meteorological Society / Environmental Protection Agency Regulatory Meteorological (AERMET) model. Hourly meteorological observations of 2 m temperature, cloud cover, 10 m wind speed, and 10 m wind direction from 1998 to 2002 were used to run AERMET. The AERMET model uses a simple 2-D time varying heat flux equation to estimate the growth of the daytime convective boundary layer. Observations from late afternoon soundings (00 UTC) in Pittsburgh, PA and Salt Lake City, UT were in good agreement with AERMET estimated mixing heights. AERMET was able to resolve large daily differences in mixing heights due to varying cloud cover, topography, and surface temperature. The five-year urban mixing height climatologies show that close proximity to oceans increases average mixing heights during the winter but restricts boundary layer growth during the summer. High elevation cities are shown to have the highest average mixing heights during the summer months. Large diurnal variations in the planetary boundary layer height are seen during the summer months while there is much smaller variation during the winter.
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