Budgets of Turbulent Energy and Temperature Variance in the Transition Zone from

[摘要] Transition from the surface layer to the free convection layer of the unstable atmospheric boundary layer is discussed mainly from the standpoint of the budget relations of thermal variance and kinetic energy. The data used here cover a wide range of stability for unstable conditions (0.1<-z/L<62) obtained over the Bonneville Salt Flats Utah in 1970. The dimensionless terms in the budget equations obey the Obukhov's similarity law. The thermal variance transport term changes sign from divergence to convergence around -z/L =1as-z/L increases. This is approximately balanced by the difference between the production and the dissipation rate throughout the analyzed stability range. Dissipation rates of kinetic energy and temperature fluctuations are well related to the spectral peak wavelength. The spectral peak wavelength and the length scale determined by the dissipation and the total variances decreases with - z/L for temperature fluctuations, but increases for vertical velocity fluctuations. They approach the same constant value for large - z/L.For strong instability those terms obey the free convection similarity law. The critical height and the stability at which this law becomes valid (the height of the transition) lies in 1<-z/L<5.

[学科分类] 大气科学