City-scale cooling and thermal comfort: A dual-index comparison of heat mitigation strategy effectiveness across geographically-diverse cities

We present an analysis of city-wide heat mitigation strategies across Madrid, Vienna, and Singapore, cities with diverse climatic and geo-topographical conditions and anthropogenic heat (AH) profiles. The study utilises an AH-assimilated climate model (mWRF_SG) and a dual-index approach that separately captures (i) thermal comfort, represented by the Net Effective Temperature (NET) indicator, and (ii) the atmospheric thermodynamic state, represented by equivalent potential temperature ( θ e ) as an indicator of moisture changes. We compare common city-wide heat mitigation strategies grouped into roof-based (white roof, green roof, and rooftop photovoltaic panels), vegetation-based (increasing urban vegetation fraction), and AH reduction categories (improved building efficiency and electric vehicle adoption). Results indicate that the relative effectiveness of these strategies is highly dependent on local-to-regional climate and context. White roofs produce the strongest daytime NET cooling in Madrid and Vienna, reflecting substantial albedo-driven reductions in surface heating, whereas their impact in Singapore may be limited by cloud cover. Increasing the urban vegetation fraction yields the strongest cooling in Singapore, where moisture availability is higher relative to drier European climates. Building-envelope efficiency improvements are most effective in Vienna and Madrid, particularly at night, owing to the prevalence of older buildings with poor insulation and the strong influence of reduced nocturnal heat retention on nighttime thermal comfort. Traffic-related AH reductions through EV adoption are most effective in cities with high baseline traffic emissions, with effectiveness further shaped by the timing of diurnal traffic peaks and boundary-layer stability. Crucially, cooling strategies that reduce NET may increase atmospheric moisture in humid contexts like Singapore, with potential implications for precipitation, while in drier climates (Madrid, Vienna), multiple strategies reduce both NET and near-surface equivalent potential temperature. The dual-index applied allows for capturing these trade-offs, highlighting that commonly promoted mitigation measures require climate-sensitive, multi-criteria planning to balance human comfort with broader environmental impacts, thereby supporting sustainable and resilient urban development. • Dual-index assessment links thermal comfort and atmospheric thermodynamic responses. • Cooling effects of white roofs and vegetation vary across climate and urban context. • Building efficiency and EVs reduce anthropogenic heat with strong diurnal effects. • Cooling strategies can influence atmospheric thermodynamics beyond thermal comfort.