Adachi, Sachiho A., Japan Agency for Marine-Earth
Science and Technology, Japan, Hiroyuki Kusaka, University of Tsukuba, Japan,
Michael G. Duda, NCAR, Manabu Kanda, Alvin Christopher Galang Varquez, Makoto
Nakayoshi, Tokyo Institute of Techonology, Japan, Motohiko Tsugawa, and Fujio
Kimura, Japan Agency for Marine-Earth Science and Technology, Japan
Anthropogenic heat,
urban fraction, and building height (roughness length, displacement height) are
major urban parameters expressing the urban characteristics such as human
activity, land use, and urban geometric structure in an urban model. In the
single-layer urban canopy model of the existing Weather Research and Forecast
(WRF) model, urban areas are categorized into only three types of urban,
defined by different set of values of urban parameters. Hence the WRF model
cannot reproduce the inhomogeneity in urban area. This study modifies the WRF
model to treat the horizontal distribution of the urban parameters in order to
express the spatially inhomogeneous urban texture.
The simulations of heat
island in summer and winter in Tokyo metropolitan area (TMA) are conducted
using the original WRF and the modified WRF. The reproducibility of the heat
island in TMA is improved in the modified WRF compared with the original one.
The improvement of anthropogenic heat has the large impact on the nighttime
surface air temperature under the strong atmospheric stability near the ground
surface, while its impact is small on the daytime surface air temperature in
summer. The urban fraction makes relatively large impact on the summertime
surface air temperature.