Abstract
For urban weather finescale forecasting, obtaining accurate and up-to-date urban canopy parameters (UCPs) is necessary and still a challenge. In this study, a high-resolution dataset of UCPs was developed by using vector-format building information and then applied in the WRF/urban system with the single-layer urban canopy model (SLUCM)/building effect parameterization (BEP) model to improve the urban finescale forecasting of a typical heat wave event during summer 2016 in Hangzhou. A series of sensitivity experiments were conducted, and the results showed that the high-resolution UCP data improved the model skill in simulating the spatial distributions and diurnal variations of 2-m temperature, 2-m relative humidity, and 10-m wind speed in the urban areas of Hangzhou, especially for the BEP model. Better results were produced when refining the computation domain due to more realistic urban morphological characteristics were adopted. The sensitive experiments suggest that the high-resolution UCPs played a significant role in representing the UHI effect though changing the surface thermodynamic parameters (e.g., roughness length), hereafter increasing the sensible heat and surface heat flux, and finally resulting a notable urban heat island (UHI) effect.
Highlights
Continuous and rapid urbanization across the world has drawn a great deal of attention to urban climate studies in the past decades (Arnfield, 2003; Grimmond, 2007; Seto and Shepherd, 2009; Stewart, 2011; Jankovic, 2013; Wang and Yan, 2016; Luo and Lau, 2018, 2021; Masson et al, 2020b)
The observed temperature was well consistent with the urban area illustrated in Figures 1b, 2B, which shows the development of urban heat island (UHI) effect in downtown Hangzhou, Bingjiang, and Xiaoshan District (Figure 4E)
It is shown that the “default” cases underestimated the near-surface temperature and with the position slightly northeastward in Figures 4A,C for the Single-layer urban canopy model (SLUCM) and building effect parameterization (BEP) models, respectively
Summary
Continuous and rapid urbanization across the world has drawn a great deal of attention to urban climate studies in the past decades (Arnfield, 2003; Grimmond, 2007; Seto and Shepherd, 2009; Stewart, 2011; Jankovic, 2013; Wang and Yan, 2016; Luo and Lau, 2018, 2021; Masson et al, 2020b). In order to represent the impacts of the complex urban geometry, two urban canopy schemes with different degrees of freedom to parameterize urban surface processes were coupled to WRF/Noah model. Since the internal temperature of buildings is kept constant in BEP, Salamanca et al (2010) developed a simple building energy model (BEM) to improve the estimation of energy exchanges between internal buildings and outdoor atmosphere. These progresses represent the most recent updates to mesoscale urban parameterizations
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