The Vertical Profiles of the Turbulence Quantities in the Atmospheric Boundary Layer

[摘要] In order to derive simple relations expressing the vertical profiles of turbulence quantities such as the rms values of vertical speed δw and temperature δT, the vertical diffusion coefficient for momentum KM, and the dissipation rate of kinetic energy ε in the planetary boundary layer (PBL), the similarity hypothesis, which was attributed to Monin and Obukhov (1954) and verified in the constant flux layer (CFL), is extended. Unlike the CFL, the horizontally homogeneous PBL is, in general, non-stationary. However, here, approximately stationary conditions are dealt with by taking sampling times for the turbulence quantities which are relatively short when compared with the time change of the conditions. As in the case of the CFL, the fundamental quantities which determine the structure of the PBL are the vertical flux of sensible heat q, and momentum u*, and scale of turbulence l. However, in the PBL, these differ from their CFL behavior q and u* vary with height z, and l is not linearly proportional to z.In the present PBL model, the height variations of q, u*, and l are expressed by suitable empirical relations and the layer thickness is defined by the height at which the extrapolated values of q and u* tend to zero.The vertical profiles of the turbulence quantities in the PBL are derived by replacing q0, u*0, z (suffix o denotes surface value) in the relations for the CFL by q, u* and l.The derived relations are compared with observation and the characteristics of the scale l are considered.

[学科分类] 大气科学