Qualitative Observational Analysis of the Boundary Layer Structure Using Surface-based Tower and Remote Sodar Data

A combination of data, from an Environmental Protection Agency portable 10 meter tower and two portable SODAR's, are used to study the variation of mean and turbulence parameters in the Research Triangle Park area of North Carolina. One SODAR transmits at a frequency of 2000 with a range from 60 to 1500 meters at 30 meter intervals. The second transmits at 4500 Hz with a range from 15 to 200 meters at 5 meter intervals. Both provide wind speed/direction, vertical velocity, and wind component variances. The 10 meter tower has wind sensors at 2, 5, and 10 meters along with temperature and relative humidity at 2 and 10 meters. Data from the 10 m tower is combined with the SODAR observations to construct vertical profiles of mean wind speed, mean wind direction , and turbulence in addition to boundary layer depth.

In addition to data collected from the above instrumentation, routine surface observations (temperature, winds, relative humidity, insolation, barometric pressure, and precipitation) provided by the National Weather Service and State Climate Office of North Carolina, are being examined. Boundary layer parameters (for example: surface heat flux, mixing depth and stability classification) are derived based on the combined data. Diurnal and spatial variations of these boundary layer parameters are of particular interest in this study. Variations over regions of differing land use such as urban and rural areas will be presented. Consideration is being given to better account for these variations in routine air pollutant dispersion models.