2.1
Survey of the History of the Urbanization of Numerical Mesoscale Models
Robert D. Bornstein, San Jose State University, San Jose, CA; and K. J. Craig
The paper presents the history of the various techniques used in numerical mesoscale models to reproduce the effects of urban areas on simulated boundary layer thermodynamic and dynamic fields. Model urbanization is carried out to better reproduces urban effects on transport patterns and on passing weather systems. The simplest approaches treat cities as a "sand box," whose radiative, thermal, and aerodynamic properties are specified for use in the surface energy and moisture boundary conditions. On the other end of the spectrum of approaches, is inclusion of urban "building blocks," whose grid-averaged heights are added to natural topographic height values. While this simulates observed urban-barrier divergent-flow effects, it does not allow for effects from street canyon flows. Recent attempts have thus focused on "porous flow" simula-tions, in which atmospheric and building-material densities are weighted on a grid volume basis. Other recent approaches include urban canyon resistance parameterizations, surface drag coef-ficients, soil heat storage parameterizations, satellite derived spatial distributions of albedo and soil moisture, and linkage of numerical urban mesoscale models with CFD urban neighborhood scale models. In such linkages, the lower boundary values of mesoscale models are provided by output from the smaller scale model, and/or the upper boundary values of the smaller scale model are provided by output from the mesoscale model.
Session 2, Urban boundary layer: models
Monday, 20 May 2002, 10:30 AM-12:15 PM
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