Coupling SUMO traffic simulator with PALM microscale urban climate model to assess the impact of traffic waste heat on urban microclimates

The transportation sector is a major contributor to global energy consumption, typically accounting for 15% to 30% of total end-use energy across different regions. The associated waste heat emissions from vehicles can substantially influence urban microclimates. To investigate this impact on near-surface air temperatures, we present a novel coupling of the traffic simulator SUMO with the microscale, building-resolving urban climate model PALM. SUMO simulates traffic dynamics within a predefined street network and calculates fuel consumption for each vehicle and time step. From these data, we derive sensible heat and moisture emissions, which are then aggregated onto PALM's computational grid. During simulation, PALM integrates these emissions into grid cells above street surfaces and calculates the effect on the near-surface meteorological conditions in the whole domain. We apply the coupled SUMO-PALM system to a case study in Berlin, Germany, using known traffic count data, and evaluate the results against near-surface air temperature measurements. This coupled SUMO-PALM system presumably offers a powerful tool for estimating near-surface air temperatures in urban areas and to show the role of traffic-emitted heat in shaping urban microclimates. Its application can support urban planning and climate mitigation strategies by quantifying the localized impacts of transportation on urban thermal environments.