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Abstract Different heat mitigation technologies have been developed to improve the thermal environment in cities. However, the regional impacts of such technologies, especially in the context of a tropical city, remain unclear. The deployment of heat mitigation technologies at city‐scale can change the radiation balance, advective flow, and energy balance between urban areas and the overlying atmosphere. We used the mesoscale Weather Research and Forecasting model coupled with a physically based single‐layer urban canopy model to assess the impacts of five different heat mitigation technologies on surface energy balance, standard surface meteorological fields, and planetary boundary layer (PBL) dynamics for premonsoon typical hot summer days over a tropical coastal city in the month of April in 2018, 2019, and 2020. Results indicate that the regional impacts of cool materials (CMs), super‐cool broadband radiative coolers, green roofs (GRs), vegetation fraction change, and a combination of CMs and GRs (i.e., “Cool city (CC)”) on the lower atmosphere are different at diurnal scale. Results showed that super‐cool materials have the maximum potential of ambient temperature reduction of 1.6°C during peak hour (14:00 LT) compared to other technologies in the study. During the daytime hours, the PBL height was considerably lower than the reference scenario with no implementation of strategies by 700 m for super‐cool materials and 500 m for both CMs and CC cases; however, the green roofing system underwent nominal changes over the urban area. During the nighttime hours, the PBL height increased by CMs and the CC strategies compared to the reference scenario, but minimal changes were evident for super‐cool materials. The changes of temperature on the vertical profile of the heat mitigation implemented city reveal a stable PBL over the urban domain and a reduction of the vertical mixing associated with a pollution dome. This would lead to crossover phenomena above the PBL due to the decrease in vertical wind speed. Therefore, assessing the coupled regional impact of urban heat mitigation over the lower atmosphere at city‐scale is urgent for sustainable urban planning. 

Abstract. This study proposes a novel structural self-organizingmap (S-SOM) algorithm for synoptic weather typing. A novel feature of theS-SOM compared with traditional SOMs is its ability to deal with input datawith spatial or temporal structures. In detail, the search scheme for thebest matching unit (BMU) in a S-SOM is built based on a structuralsimilarity (S-SIM) index rather than by using the traditional Euclideandistance (ED). S-SIM enables the BMU search to consider the correlation inspace between weather states, such as the locations of highs or lows, that is impossible when using ED. The S-SOM performance is evaluated by multipledemo simulations of clustering weather patterns over Japan using theERA-Interim sea-level pressure data. The results show the S-SOM'ssuperiority compared with a standard SOM with ED (or ED-SOM) in tworespects: clustering quality based on silhouette analysis and topologicalpreservation based on topological error. Better performance of S-SOM versusED is consistent with results from different tests and node-sizeconfigurations. S-SOM performs better than a SOM using the Pearsoncorrelation coefficient (or COR-SOM), though the difference is not as clear as it is compared to ED-SOM.