THEORETICAL STUDIES OF THE ATMOSPHERIC BOUNDARY LAYER. PARTS I-III

Three separate studies concerning flow over inhomogeneous terrain are presented. Two-dimensional nonlinear models were constructed and then integrated numerically. In the first study, the atmospheric boundary layer flow over terrain with a discontinuous variation in roughness was studied. A time dependent numerical model, using Blackadar's expression of mixing length and assuming no dynamic pressure effect and no vertical displacement of the zero velocity level at the lower boundary, was integrated until a steady-state situation was reached. The results agree with earlier theoretical work of Panofsky and Townsend and also with observations by Sterns and Lettau. The second study represents an attempt to solve a problem similar to the one just described using a steady-state model. An iterative method for solving the equations was derived. In addition, the dynamic pressure effect was also incorporated. The results show satisfactory agreement with those of Panofsky and Townsend. It is found that the dynamic pressure effect causes an apparent horizontal smoothing of the motion field. In the third study, the effect of an isolated hot surface (10 km wide) on the motion and temperature field is investigated. The model is time dependent and is based primarily on a sea breeze model by Estoque. As expected, the results show that the intensity of the upward motions which are induced is inversely proportional to the strength of the prevailing flow. The perturbations in both the temperature and velocity fields extend to several tens of kilometers downwind of the hot surface.