Review of Japanese Urban Models and a Scale Model Experiment - Meteorological and Air Quality Models for Urban Areas - page 31

Chapter 5
Review of Japanese Urban Models and a Scale
Model Experiment

Manabu Kanda

Abstract Numerical models including simple urban canopy models and computa-
tional fluid dynamic technologies developed in Japan and the Comprehensive Out-
door Scale MOdel (COSMO) experiment are reviewed.

5.1 Urban Models Developed in Japan

5.1.1 Simple Urban Canopy Models in Japan

Simple urban canopy models in Japan can be classified into two categories: (1) resis-
tance network analogy (Kusaka et al., 2001; Kanda et al., 2005a) and (2) addition
of sink/source terms to the basic equations (Uno et al., 1989; Ashie et al., 1999;
Vu et al., 1999, 2002; Tanimoto et al., 2004; Kondo et al., 2005). The basic con-
cepts were derived from similar vegetation models. However, vertically 1D approx-
imations used in the parameterization of momentum and energy absorptions within
the vegetation canopies are no longer valid for urban canopies. Special treatment
of the 3D surface geometry is required instead. Urban radiation schemes typically
include complicated sunlit and shade distributions with 2D (Kusaka et al., 2001) or
3D geometry (Ashie et al., 1999; Kanda et al., 2005b; Kondo et al., 2005). Parame-
terization of local transfer coefficients for momentum and scalars between surfaces
(e.g., roof, street, walls) and a reference height requires more than a 1D approxi-
mation. However, a compilation of experimental data suggests that such coefficients
largely differ case by case and thus are difficult to arrange in a simple formulation
(see review Hagishima et al., 2005).
Implementation of simple urban canopy models into mesoscale weather fore-
cast systems is a realistic way to generate routine predictions without excessive
computational load. Several numerical studies have included mesoscale simulations

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Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
e-mai: [e-mail]

M. Kanda (