Effect of urbanization on gust wind speed in summer over an urban area in Eastern China

Abstract

Previous studies have extensively examined effects of urbanization on mean wind speed, but few studies were aimed at gust wind speed, while large wind gust could cause safety and economic hazard to a variety of activities. In this study, the effect of urbanization on the gust wind speed in Nanjing, China is assessed using the Weather Research and Forecasting model (WRF) with a parameterization of the gust wind speed. The WRF simulations are run for the summer period of 2013 with the underlying surface before and after the urbanization. The results indicate that although the mean wind speed is reduced, the gust wind speed in the urban areas is increased significantly due to the enhanced friction velocity and less atmospheric stability induced by the urbanization, while the contribution of deep convection is relatively small. The gust wind speed increases more in the nighttime (0.6-0.9m s-1) than in the daytime (less than 0.3m s-1), since the turbulence is enhanced more in the nighttime than in the daytime after the urbanization. The probability distribution shows that the increase of gust wind speed is mainly between 0.0-0.5m s-1 in the urban areas. In different urban land categories, the increase of the gust wind speed is larger in the commercial or industrial areas than in high-intensity and low-intensity residential urban areas. Averagely, the gust wind speed in the entire city after the urbanization increases by 0.02, 0.36 and 0.19m s-1 for the daytime, nighttime and daily mean, respectively.

Effect of cooling roofs on gust wind speed over an urban agglomeration in Southern China

“…The daily mean wind shear raises 0.25-0.40 m s −1 (25%-40%) and 0.10-0.25 m s −1 (15%-30%) caused by WRs and GRs in the PRD region, respectively. The larger effect of WRs on wind shear is because the variations of the mean wind speed at 850-hPa pressure level caused by WRs are not significantly different from those by GRs, while the mean wind speed at 950-hPa pressure level is more reduced by WRs than by GRs (as shown in figures S9 and S10), as the mean wind speed at 850-hPa pressure level is less impacted by the urban boundary layer than the mean wind speed at 950-hPa pressure level is (Liu et al 2023).…”

“…Wind gust with large momentary wind speed is a disastrous weather that may induce great socioeconomic impacts as it could cause serious damage to infrastructures such as bridges and power lines, traffic and transportation, industrial and agricultural production, and human safety (Fink et al 2009, Suzuki 2009, Suomi et al 2013, Hawbecker et al 2017, Montenegro et al 2020. Therefore, it is need to develop strategies to mitigate wind gust, especially over urban areas where the above elements are concentrated (Liu et al 2023). Gust wind speed, by which wind gust does harm, is defined as the maximum value in a time series of three-second moving average wind speed during a ten-minute period (World Meteorological Organization 2014).…”

“…However, there have been few researches investigating the impact of urbanization on wind gust. Liu et al (2023) evaluated the impact of urbanization on gust wind speed in Nanjing megacity, China, finding the gust wind speed was increased by urbanization due to strengthened turbulent flow in the planetary boundary layer (PBL), although in the meantime the mean wind speed was decreased. Therefore, urbanization deteriorates the urban environment not only by raising air temperature and worsening air quality but also by increasing the gust wind speed.…”