Influência da superfície na estrutura da camada limite atmosférica noturna

Abstract

The night boundary layer presentes two contrastingly diferente regimes,which is clas-sified by the intensity of the turbulence. The very stable flow regime is characterized by weak winds and clears kies, corresponding to Strong radiative cooling at the surface, causing weak and possibly intermitente turbulence. On the other hand, the weakly stable regime occurs in the presence of Strong Wind sand/or cloud cover. There are diferente ways to determine the regimes, both from the point of view of internal parameters, suchs Richardson number, and external parameters, such as geostrophic wind, cloud cover among others. In this work, the strategy used implies that at any given circumstance a VSBL or WSBL exists, but in diferente layers. Thus, analyzing the velocity profile in both formulations (CC and CL-Sand, Clay and Peat) it is possible to verify the formation of a jet stream, with its maximum peak located at 95.45m. The temperature profile shows that CC formulations are colder than CL near the surfaces, this occurs because CL formulations are more turbulent. Analyzing the average dependence of VTKE as a function of local Wind speed, it is possible to verify the transition at both levels and in both formulations. For the cloud cover effect, it can be seen that even though the effectis relatively small, in clear sky, higher geostrophic Wind speeds are required for the regime change. About the vertical structure of the boundary layer, one realizes that surfaces with low termal conductivities have a shallower CLE. When analyzing the stability functions, CL formulations reproduce a deeper CLE. Increased cloud cover contributes to a thicker CLE in both formulations and surfasse conditions.