A study of convective elements in the atmospheric surface layer |
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| Authors: | A Shelby Frisch Joost A Businger |
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| Institution: | (1) Dept. of Atmospheric Sciences, University of Washington, 98105 Seattle, Wash., USA;(2) Present address: Wave Propagation Laboratory, National Oceanic and Atmospheric Administration, USA |
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| Abstract: | A statistical model, based on a method of Vulf'son, is used to examine some of the plume-like temperature structures formed in the unstable boundary layer. The model assumes that the plume diameter changes slowly with height so that a cylindrical approximation may be made. Measurements of the vertical velocity and temperature were used to determine the temperature dependent portion of the vertical velocity field. Temperature data were collected from sensors on a tower and from aircraft; velocity data were collected only from the tower.Using this model for analysis of the data indicates that: (1) the average isotherm diameter and the population of isotherms are a function ofz/L; (2) the distribution of core temperatures is approximately a uniform distribution.Independent of the model, a convective velocity was determined and found to have approximately the same profile as the temperature; from this the average velocity of the plumes was found to be a linear function ofz/L, fromz/L  - 0.1 toz/L - 1.0. As a consequence of this functional dependence, the entrainment into the plumes is approximately constant over this range. The cumulative temperature distribution function was found to be an asymmetric function ofz/L. A simple relation which is independent ofu
* is given to determine the heat flux.Contribution No. 269 Dept. of Atmospheric Sciences, University of Washington. |
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