Turbulent Boundary Layer

An important parameter in both weather and climate models is the depth of the turbulent boundary layer. The depth of this layer determines the strength of vertical mixing of pollutants and the daily variation of surface temperature and moisture. The depth of the boundary layer can affect the vertical profile of wind speed near the surface, and thereby influence the amount of energy available for wind turbines. The boundary layer also frequently determines the amount of convective potential energy available to fuel summertime thunderstorms. Despite its importance, the depth of the turbulent boundary layer is rarely measured.

Methods

PSD has developed a method to automatically detect the depth of the convective turbulent boundary-layer using observations from wind profiling radars. Three radar parameters are used in the calculation of the boundary layer depth: radar reflectivity, variance of vertical velocity, and spectral width (a measure of the turbulence). A fuzzy-logic based algorithm combines measurements of the vertical profiles of all three parameters to determine the depth of the turbulent boundary layer.

Activities & Outcomes

The automatic boundary layer depth algorithm has been applied to data from networks of wind profiler radars from several air quality field programs. It is now also being applied in real-time to several of PSD's 915 MHz wind profilers deployed for various field programs. We provide these real-time boundary layer depth values to the National Weather Service's National Center for Environmental Prediction for evaluating NOAA's operational weather forecast models.

thunderstorm 2005 (Image courtesy NWS Birmingham, AL)
Thunderstorm in 2005 (Image courtesy NWS Birmingham, AL)