Parameterization of Inversion Breakup in Idealized Valleys. Part II: Thermodynamic Model

Abstract

A simple thermodynamic parameterization based on a modified version of the Whiteman and McKee inversion destruction model is presented to simulate the evolution of vertical temperature structure during the inversion breakup period in idealized valleys under clear, undisturbed weather conditions. The proposed method adopts simplified semiempirical parameterizations of radiation and surface energy budgets at the valley floor and sidewalls and an empirical scheme for the partitioning of energy in the valley atmosphere, eliminating the need for selecting arbitrary values for the adjustable model parameters. The model accurately simulates the changes with time of the height of the inversion top and the depth of the convective boundary layer during the breakup of nocturnal temperature inversions in a wide range of valley topography. The theoretical estimates were validated and compared with dynamical model predictions and actual measurements. Because of its simplicity and its fair agreement with observations, the proposed method may be useful in applications in boundary layer, air pollution, and complex terrain meteorology. It is recognized that more work is necessary before the validity of the suggested procedure can be fully established.