Extended Abstract (240K)P4.19
Monin-Obukhov similarity functions of the structure parameter of temperature and TKE dissipation rate in the Stable Boundary Layer (Formerly Paper 9.14)
Oscar K. Hartogensis, Wageningen University, Wageningen, Netherlands; and H. A. R. De Bruin
The Monin-Obukhov similarity theory (MOST) functions f_eps and f_T, of the dissipation rate of TKE, eps, and the structure parameter of temperature, CT2, were determined for the stable atmospheric surface layer using eddy correlation data gathered in the context of CASES-99. This data-set covers a relatively wide stability range, i.e. z/L of up to ~10, where z is the height and L the Monin-Obukhov length. The best fits were given by f_eps = 0.8 + 2.5z/L and f_T = 4.7(1+1.6(z/L)^2/3), which differs somewhat from previously published functions. Several explanations for these found differences are discussed: the use of the planar fit method to orient the sonic axis along the mean flow, the short flux averaging intervals of 5 minutes used to exclude non-turbulent flux contributions, and eps was obtained from longitudinal wind velocity spectra using a time series model (ARMA) method instead of the traditional Fourier transform. The neutral limit f_eps = 0.8 implies that in the simplified TKE budget equation there is an imbalance between TKE production and dissipation. Similarly, we found a production-dissipation imbalance for the temperature fluctuation budget equation. Correcting for the production-dissipation imbalance, the 'standard' MOST functions for dimensionless wind speed and temperature gradients (phi_m and phi_h) were determined from f_eps and f_T and compared with the fm and fh formulations reported in the literature. We found good agreement with the Beljaars and Holtslag (1991) relations. Last, the flux- and gradient Richardson numbers are discussed also in terms of f_eps and f_T.
Beljaars, A.C.M., and Holtslag, A.A.M.: 1991, ‘Flux parameterization over land surfaces for atmospheric models’, J. Appl. Meteor. 30, 327-341.
Poster Session 4, Boundary Layers
Tuesday, 10 August 2004, 5:30 PM-5:30 PM, Casco Bay Exhibit Hall
Previous paper