Downwind Warming of Cities? Inequal Heat Distribution Attributed to Winds

Abstract

Heat exposure within urban areas is strikingly uneven, posing disproportionate risks to certain communities. While nature-based solutions have gained attention, the role of wind in distributing heat remains less understood in an urban planning scale. This study assessed the interaction between wind direction, speed, and heat advection in Taipei Basin during summers from 2011 to 2020, using data from densely installed meteorological stations. A novel method was developed to capture multiple wind directions while accounting for local terrain and urban effects. Results revealed that wind-induced heat advection is complicated by local terrain and nearby cities in the conurbation, varying heat distribution. Windy conditions were mostly warmer than calm conditions, with north-westerly and westerly winds causing the strongest heat advection. Heat advection increased with wind speeds up to 5.4 m/s and decreased thereafter. Substantial intra-urban differences in heat advection were observed, reaching 4.33°C daytime and 3.34°C nighttime. Upwind areas were not necessarily cooler, while some downwind areas at mountain foot experienced greater warming. Up to 2.6SD of advected heat magnitude was found downwind at night. These findings underscore inequitable heat transfer to areas that do not generate heat and the critical need for wind-sensitive planning for both city-region and inter-urban areas.