WRF-LES Simulation of Wind Flow over Rough Urban Surface during Typhoon Lan (2017)

Abstract

In this study, we investigated the influence of ground surface boundary conditions of the meteorological model on the accuracy in predicting the mean wind speed and wind speed fluctuation in the urban area. Two types of ground surface boundary conditions (Cases 1 and 2) were created. In Case 1, the roughness length for the urban area was set to 0.5 m uniformly, whereas in Case 2, the spatial distribution of roughness length for the urban area was set based on the urban geometry. We performed the wind flow simulation in the central part of Tokyo during Typhoon Lan (2017) by using WRF-LES with the created ground surface boundary conditions. By setting the roughness length based on the urban geometry, the accuracy in predicting the mean wind speed was improved significantly. However, in both cases, WRF-LES underestimated the turbulence intensity, especially near the ground surface.

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