2.1.5 Urban planning
Urban planning is concerned with the design and development of urban environments, including population control, transport management, and building distributions. The energy consumption, water usage, and the building construction in a city are closely related to urban planning, which have important effects on the weather and climate by affecting the energy, water cycle, and urban meteorology. In CAS-LSM, the schemes of AHR, UWU, and urban roughness height (and height variations) were incorporated to consider the effects of these processes.
AHR was treated as part of the sensible heat flux that affected the energy balance equation. AHR could be divided into four components: AHR from vehicles, the building sector, industry, and human metabolism (Sailor and Lu 2004), representing the major sources of waste heat in the urban environment. As anthropogenic heat is closely tied to energy consumption (Sailor 2011), the AHR from vehicles, buildings, and industry could be estimated by listing all kinds of energy consumption (including coal, coke, crude oil, gasoline, kerosene, diesel, fuel oil, natural gas, and electric power). For UBU, a simple UBU scheme, including urban irrigation and road sprinkling, was incorporated into the CAS-LSM model based on the scheme described by Zeng et al. (2017). Here, ecological and farmland irrigations were both treated as urban irrigation, and the road sprinkling scheme was activated at night during the summer when water was applied to the impervious road layer to accelerate evaporation. For the urban roughness height, this parameter is affected by building construction, and the spatial distribution of urban building heights, which can affect the heat and momentum variables. Here, the scheme was based on the work of Millward-Hopkins et al. (2011). It is worth noting that because urban planning is currently used only in the regional setup, it was set as an option in the model and not used in the global coupled simulations.