||Lateral Turbulence Intensity and Plume Meandering during Stable Conditions.
Hanna, S. R. ;
||Environmental Research and Technology, Inc., Concord, MA.;Environmental Sciences Research Lab., Research Triangle Park, NC.
Atmospheric diffusion ;
Time series analysis ;
Wind velocity ;
Cinder Cone Butte ;
Atmospheric boundary layer
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There is much evidence in the literature for the presence of mesoscale lateral meanders in the stable nighttime boundary layer. These meanders result in relatively high lateral turbulence intensities and diffusion rates when averaged over an hour. Anemometer data from 17 overnight experiments at Cinder Cone Butte in Idaho are analyzed to show that the dominant period of the mesoscale meanders is about two hours. Lidar cross-sections of tracer plumes from these same experiments show that the hourly average (sigma sub y) is often dominated by meandering. Since meandering is not always observed for given meteorological conditions, it is suggested that nighttime diffusion cannot be accurately predicted without using onsite observations of wind fluctuations. In case no turbulence data are available, an empirical formula is suggested that predicts the hourly average lateral turbulence intensity as a function of wind speed and hour-to-hour variations in wind direction. (Copyright (c) 1983 American Meteorological Society.)