Introduction of urban momentum and thermal drag effects in the asymmetric convective model version 2 (ACM2) in the weather research and forecasting (WRF) model

Abstract

Due to increase in population and rapid economic development, more and more buildings are built in developing countries. Building density and alignment will cause wind blockage problem, resulting air pollutants are trapped within the cities, cause poor air quality and threatening our health. The study of urban meteorology and air quality is important to human beings on their health issues. Cities are classified as the urban categories in the 24-class USGS land-use classification with high roughness length as the characteristics and Monin Obukhov Similarity Theory (MOST) is traditionally applied to simulate boundary layer dynamics based on surface energy fluxes resulted in over-prediction in wind speed and under-prediction in temperature in night time in the weather forecast. Momentum and thermal drag effects together with a building energy model are crucial to represent the presence of buildings impact on momentums and thermals in the boundary layer. In this thesis, a realistic and efficient multi-layer approach will be introduced to the ACM2 model in the WRF model. Sensitivity tests to the urban morphological parameters in idealized simulations are analysed and the results are consistent to the physics. Simulations based on real urban morphological data are also performed. We will show there are significant improvements on wind prediction. The new urban scheme is proven to be realistic and efficient especially for operational purposes.

Date of Award	2017
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology