Dependence of friction velocity on the wind velocity in the surface air layer
V.A. Gladkikh, V.P. Mamyshev, I.V. Nevzorova, S.L. Odintsov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: surface layer, wind velocity, friction velocity, turbulence
Abstract
The friction velocity (dynamic velocity) u * enters into nearly all computational schemes used for forecasting the state of the atmosphere. To find this velocity, it is necessary to know the mixed moments of turbulent components of the wind vector. However, the information about turbulence is lacking at the initial stage of forecast. That is why model equations are usually used for u *. These equations are based on the relation of the friction velocity to the horizontal wind velocity Vh . In this work, we considers the empirical relations u *( Vh ) for various conditions (different time of the day, seasons, types of stratification, observation sites, and measurement altitudes). Initial experimental data used to derive these relations were obtained by ultrasonic meteorological stations operating in the surface air layer at different observation sites.
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