Hiroyuki KUSAKA, Center for Computational Sciences, University of Tsukuba, Japan
Ryosaku IKEDA, Weathernews Inc, Japan
Takuto SATO, Center for Computational Sciences, University of Tsukuba, Japan
Taisuke BOKU, Nagoya University, Japan
Satoru IIZUKA, Center for Computational Sciences, University of Tsukuba, Japan
Meso-scale and micro-scale meteorological models have been largely contributing to urban climatology. This talk will introduce highlights of city-scale meteorological modeling efforts by our group, specifically the new version of our own city-scale large eddy simulation (LES) model named City-LES (Ikeda et al. 2015). Additionally, simulation results are also introduced. The main features of our model are as follows. (1) This model numerically and three-dimensionally simulates/predicts the time-varying spatial distributions of fluid, radiations, and cloud/fog formation. (2) The dynamics core is based on non-hydrostatic Boussinesq approximation equations, considering atmospheric static stability. (3) The spatial resolution is in order of 1 to 10 m and the model can resolve buildings and roadside trees. (4) Long- and short-wave radiations are calculated three-dimensionally and multiple reflections of the radiations within urban canopy layers are considered by the radiosity method. (5) The model can evaluate the various heat stress mitigation strategies, for instance, installation of dry-mist spraying, roadside trees, cool pavements, and green/cool roofs. (6) The model outputs various heat stress indices (UTCI, WBGT, PMV, MRT). (7) The model simulations are performed with the dynamical downscaling from mesoscale meteorological models. In this study, the performance of our model was validated using observations around the Tokyo Station. The model was able to reproduce the observed data with high accuracy. For example, the model reproduced differences in surface temperatures between shaded and sunlit roads, and between each land cover. The model was also able to accurately reproduce the complex airflow and spatial distribution of heat stress indices. This high reproducibility was brought about by the ultra-high-resolution modeling and the consideration of the effects of the street trees and mist spraying in the model.
Keywords: Large Eddy Simulation|Urban Heat Island|Numerical Modeling|UTCI|Heat Stress