Urban ventilation network identification to mitigate heat island effect

Global warming and rapid urbanization aggravate the urban heat island (HI) effect significantly, and alleviating the HI effect can promote urban sustainable development and improve residents' livability. Relevant studies mainly use the single perspective of cold island (CI) or HI network to discuss the methods of mitigating HI, which ignores the potential cold and hot interaction process between CI and HI driven by complex temperature gradient inside the city, limiting the comprehensiveness of mitigation strategies to a certain extent. Therefore, it is particularly critical to establish the potential connection between CI and HI to achieve systematic optimization of urban thermal environment. Taking the main urban area of Xi'an as the research object, we combined morphological spatial pattern analysis (MSPA), landscape connectivity, circuit theory and robustness analysis to construct CI ventilation network (CIVN) and cold heat ventilation network (CHVN) from multiple perspectives and levels. CIVN identifies and strengthens the urban cold system, while CHVN establishes the airflow interaction path between CI and HI. This also reflects the impact of HI on CI, which has a far greater impact on CI than the impact from CI airflow. CIVN robustness decreases after CI is impacted by heat flow, while CIVN robustness is improved by adding CI according to urban planning and key nodes of VN. In addition, priority protection for CI with low LSI and high node degrees (Low bearing capacity and high heat flow threat) can prevent CIVN degradation. This study is expected to provide new ideas for mitigating urban HI effects, and also provide guidance for making climate-resilient urban planning and promoting urban sustainable development.