Numerical weather prediction models for urban weather require various urban parameters such as urban geometry and anthropogenic heat emission. Preparing databases of these urban parameters is essential for better reproducibility of urban weather simulation. In this paper, a database of urban geometric parameters for the whole Japan is created using a detailed building GIS. This database includes average, maximum, and standard deviation of building heights, plane and frontal area indices, roughness length for momentum, displacement height, and sky view factor. Furthermore, to expand this database to areas where detailed building GIS is not well prepared, methods of estimating the surface parameters are proposed. These methods require only a global digital elevation models and aerial imagery, which are now open to public inspection and easy to obtain. The results are compared with values derived from high-resolution building heights data.

Numerical weather prediction models have been improved to adequately represent the growing influence of urban areas to surrounding weather. Recently, updated LES-derived empirical equations on the aero-dynamic urban surface parameters displacement height d, and roughness length for momentum z0m, have been introduced. Using a high spatial resolution d, z0m, and anthropogenic heat emission distribution, dry case simulation was conducted using Weather Research and Forecasting Model with domains covering Tokyo, Nagoya, and Osaka. It was found that default WRF generally underestimate roughness. Results were also compared with actual observations of 2 m air temperature and surface wind speed, and were found to be well represented in the model when detailed parameters were used.