Objectifying Urban Climate Mapping: A Scalable Approach to Enhancing Climate-Resilient Spatial Planning

Cities and municipalities are particularly affected by climate change and its impacts. Considering climate mainstreaming, the planning sector is called upon to provide appropriate adaptation services. Many German and Austrian cities have already prepared urban climatic maps (UCM) and are partially integrating them in their spatial planning policies. These UCM usually contain two components: an urban climatic analysis map (UC-AnMap) and an urban climatic planning recommendation map (UC-ReMap). In German speaking countries the compilation is often based on the VDI (Association of German Engineers) directive 3787 (Climate and Pollution Maps for Cities and Regions), which provides a conceptual guideline, but is open to design and interpretation and leaves the actual implementation to engineering firms and consulting agencies.

The research project “OSCAR - Objectifying and Standardizing Urban Climate Analyses for Climate-Resilient Urban Planning” (funded by the Climate and Energy Fund and carried out under the program "Austrian Climate Research Programme (ACRP)") identified three major shortcomings in the development process of UCM: (1) Lack of standards and comparability, (2) high development costs, as the methods and recommendations must be developed and elaborated individually in each case, and (3) insufficient trust in provided data and maps for planning decisions due to poor documentation or missing understanding to applied methodologies and results.

OSCAR aims to provide solutions to close identified gaps by preparing the basis for a good practice and objectification opportunities. A comprehensive literature review and stakeholder-engagement process based on expert interviews and workshops with urban climate modeling experts, consulting agencies and city representatives provides the theoretical and practical groundwork for the research and methodological advancements. Within the project, one central objective is the development of an objectified and reproducible model for UC-AnMaps, based on the VDI directive to (i) accelerate the assessment of urban climate conditions, (ii) provide a basis and method to make climate adaptation measures numerically and rapidly tangible on a city scale level, (iii) enable comparability of urban climate conditions of a city over time and (iv) provide secured planning recommendations through reproducible and well documented methods. Aligning with the recently update draft of the “Climate and Planning” guideline (VDI 11/2024) to develop UC-AnMaps, a reproducible calculation method for spatial designation of climatopes (areas of similar climatic characteristics), and partial integration of specific climate phenomena is under ongoing development. To use the developed method without data constraints, publicly available data and open-source software is a prerequisite.

The envisioned approach is based on weighting of static input data (e.g. imperviousness density), a rudimentary cold air flow algorithm, logical combinations of spatial data sources, and presupposing factors (e.g. area sizes) to define climatopes. In-depth documentation, strengths and limitations of the suggested method, along with a conceptual model and case studies provide promising results for scaling and accelerating the development of UC-AnMaps. Regarding derived planning recommendations, findings of the stakeholder-engagement formats suggest, that a close exchange with urban stakeholders for developing the UC-ReMaps is crucial and shall not be replaced by a reproducible and quantified information provision about urban climate conditions.