A COMPARISON OF METHODS USED TO ESTIMATE THE TURBULENT KINETIC ENERGY DISSIPATION RATE IN THE ATMOSPHERIC SURFACE LAYER

Open Access
Author:
Limbacher, James Alan
Graduate Program:
Meteorology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 28, 2010
Committee Members:
  • Marcelo Chamecki, Thesis Advisor
Keywords:
  • TKE
  • dissipation rate
  • atmospheric surface layer
  • turbulence
Abstract:
We test local isotropy of second- and third-order moments in order to determine the best approach to estimating the turbulent kinetic energy (TKE) dissipation rate in the atmospheric surface layer. To further this goal, a micrometeorological field campaign was conducted between the months of Aril and July of 2009 at Rock Springs, Pennsylvania. Five CSAT3 sonic anemometers were mounted on a telephone pole at heights ranging from 0.5 m to 10 m and operated continuously at a frequency of 20 Hz for the duration of the experiment. Structure functions and turbulence spectra were computed from the data during quasi steady-state periods, and were used to calculate isotropy ratios and to estimate the TKE dissipation rates. Spectral dissipation rates show heavy dependence on corrections to Taylor’s hypothesis and spectral tapering, and significant error is introduced if these corrections are not made. As has been demonstrated in previous studies, results confirm that Kolmogorov’s four-fifths law consistently underestimates the TKE dissipation rate when compared to other indirect methods. Although our results show the third-order structure functions becoming more isotropic with height in the ensemble mean, the dissipation rates obtained from the four-fifths law fail to improve with height. We conclude that the spectral dissipation rate estimates are superior to those estimated from the four-fifths law and the second-order structure function for two main reasons: the spectrum shows a broader inertial subrange with better scaling at all heights, and local isotropy holds better for the spectra at all heights.