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Stability functions for momentum, heat and water vapour and the vertical transport of TKE and pressure fluctuations estimated from measured vertical profiles of wind speed, temperature and humidity

: Kramm, G.; Herbert, F.; Bernhardt, K.; Müller, H.; Werle, P.; Foken, T.; Richter, S.H.

Contributions to atmospheric physics 69 (1996), Nr.4, S.463-475
ISSN: 0005-8173
ISSN: 0303-4186
Fraunhofer IFU; 2002 in Helmholtz-Gesellschaft integriert

Vertical wind speed, temperature and humidity profile data from three known atmospheric field campaigns are used to determine the surface layer similarity functions for the transport of momentum and heat as well as TKE (turbulent kinetic energy) and pressure fluctuations. The basic principles on which we carry out this determination are a simplified TKE-budget equation obeying Monin-0bukhov similarity laws and a one-and-a-half-order closure concept. Least squares techniques are utilised for the calculations. The numerical analysis provides all important internal and external surface layer parameters like the friction velocity, u., the temperature and humidity scales, Theta *. and q *, the roughness length, z 0., the zero-plane displacement, d, as well as the temperature and humidity values Theta gamma and q gamma, at the height z gamma = z0 + d. With these data we can determine the individual gamma-coefficients in the empirical Businger-Dyer and O'keyps relations. This is the main inte rest of this study. It is found that the computed empirical coefficients appreciably depend on the thermal stratification in the atmospheric surface layer. These estimates document that the gamma's apparently vary so considerable within a stability regime that the usually adopted constant coefficients were not suitable in these cases. Moreover, one is led to the further important result that the parameters z0 and d found here, considerably differ from those values obtained with the conventional gamma-coefficients suggested in the literature.