Enhancing transport modelling with microclimate simulations: an interdisciplinary approach to climate adaptation modelling within the KNOWING project

As climate change is an urgent global threat, the EU’s Green Deal aims to make Europe climate-neutral by 2050, while ensuring fair and sustainable implementation. Achieving this goal requires both mitigation and adaptation measures, with a focus on understanding the interactions and trade-offs between them. One major shortcoming of current modelling approaches is the omission of interactions between domain-specific models from various fields, as they often differ in their modelling approaches. However, this is crucial in understanding the full impact of mitigation and adaptation measures, as their impact cascades into many sectors.

Among other demonstrator regions within the KNOWING project, future scenarios for the city of Tallinn (Estonia), incorporating traffic related mitigation and heat related adaptation measures are modelled in close exchange with city representatives. The traffic and transport sectors are simulated with a state-of-the-art multimodal tour-based transport model, which aims to depict passenger and freight transport activities and traffic flows for a typical workday for the status-quo, 2030, 2040 and 2050. To understand the microclimate as well as to identify heat stress hotspots of the city, the state-of-the-art model PALM-4U is used. A hot summer day with boundary conditions from a mesoscale climate model is applied to the status-quo city as well as a Tallinn of 2030, 2040 and 2050.

To capture the impact of the transport scenarios to the microclimate simulationstransport infrastructure changes have been implemented as land-use changes within PALM-4U. Desealing of street lanes as well as parking lots and added street greenery within the future scenarios is applied in PALM-4U based on the modelled changes in transport infrastructure. Vice versa, the transport model is also impacted by the microclimate model, as street canyons with high heat stress during the daytime might be avoided by cyclists and pedestrians alike.

This results effectively in a quantification of exposure for pedestrians and cyclists for each link, allowing to define additional weights for these passages within the transport model. These weights account for a disutility for pedestrians and cyclists within destination choice, mode choice and route assignment procedures. As the typical working day traffic is simulated for the entire year and the heat day simulation is only valid for some summer days, the weights derived from microclimate model are only applied as statistically appropriate for each future scenario.

Many further interactions and linkages between the two modelling approaches are still omitted, however the possible enhancement of the transport model with heat stress information from the climate model lays an important foundation for further understanding the intersectoral impacts of climate adaptation measures and adds additional value in transit-orientated development.