A two-dimensional mesoscale numerical model of an urban mixed layer—I. Model formulation, surface energy budget, and mixed layer dynamics

Abstract

A two-dimensional, numerical urban mixed layer model, which takes into account differences between the urban and the rural surfaces, as well as roughness and topographical variations over the model domain, is developed. The various land use types over the metropolitan area are specified by different proportions of concrete and grassy soil surfaces. Thermal characteristics of the vegetated soil surface are parameterized in terms of the surface soil moisture content. Distinct differences in the diurnal patterns of urban and rural surface energy budgets, which are found in some observational studies, are also obtained in some of our model case studies. Dynamics of the dome-shaped urban mixed layer is studied for the case of the stationary balanced wind. The balanced wind flow simulation can explain some of the important flow perturbations due to the urban heat island and increased roughness of the urban area.