In this study, first, three compact city models with different degrees of compactness for a prefecture in a large metropolitan area of Japan were designed. Based on the urban classifications “population-induced area,” “population-unchanged area,” and “withdrawal area,” we constructed the compact city models. Next, the impact of introducing the designed compact city models on the summer thermal environment in the 2050s was quantitatively assessed by downscaling simulations from a global scale to an urban scale. Moreover, we examined the effect of a land use change in the withdrawal area on the future thermal environment in the urban area (the population-induced and population-unchanged areas). As expected, a temperature increase in the urban area occurred due to urban densification in the compact city models. On the other hand, the temperature decrease in the urban area as a result of changing the land use of the withdrawal area, i.e., by replacing the withdrawal area with grassland, approximately offset the above-mentioned temperature increase. This implies that, in compact city planning, it is necessary to properly plan not only for the concentrated urban area but also for treatment of the withdrawal area from the viewpoint of environmental impact.

在这项研究中，首先，针对日本大都市地区的一个县，设计了三种具有不同紧凑程度的紧凑城市模型。基于“人口引起的区域”，“人口不变的区域”和“退缩区域”的城市分类，我们构建了紧凑的城市模型。接下来，通过将模拟从全球规模缩减为城市规模，定量评估了引入设计紧凑型城市模型对2050年代夏季热环境的影响。此外，我们研究了退耕区土地利用变化对城市地区（人口引起和人口不变的地区）未来热环境的影响。不出所料，由于紧凑型城市模型中的城市致密化，导致市区温度升高。另一方面，改变撤退区土地用途的结果，即通过用草地代替撤退区，市区的温度下降大致抵消了上述温度升高。这意味着，在紧凑的城市规划中，不仅需要针对集中的市区进行适当的规划，而且还必须从环境影响的角度对撤出区进行适当的规划。