Clim-Lux

Climate change and urban development are increasing the need for spatially explicit information on thermal stress and local climate functions in Luxembourg. Existing climate analyses provide an important foundation, but planning authorities and municipalities require an updated and substantially more detailed evidence base for the whole country. They need to know where heat accumulates, how cold air is produced and transported, which open spaces and ventilation pathways are essential for cooling, and how these functions may change under future climate and land-use conditions. Clim-Lux responds by combining numerical modelling, stationary and mobile measurements, future climate scenarios and stakeholder co-design in a high-resolution bioclimatic analysis for the Grand Duchy of Luxembourg.

Clim-Lux introduces three interconnected innovations that advance bioclimatic assessment from a description of present conditions to a validated and planning-oriented analysis of current and future climate risks.

• First, the project applies the validated FITNAH-3D meteorological, non-hydrostatic mesoscale model at a horizontal resolution of 5 metres across Luxembourg. The model explicitly represents topography, buildings, vegetation, sealed surfaces, water bodies and roads. It simulates near-surface air temperature, wind fields, cold-air production, cold-air volume flows and human thermal comfort during a representative summer radiation weather situation. A present-day simulation is complemented by a future scenario for 2031-2060 that integrates climate change and anticipated spatial development.
• Second, Clim-Lux combines modelling with measurement-based validation. LIST will operate autonomous air temperature sensors in five municipalities and surrounding rural reference areas for at least nine months. The LIST Environmental Measurement Vehicle will also measure air temperature transects in up to three municipalities during suitable winter and summer conditions. High-resolution, GPS-geocoded mobile measurements and continuous stationary observations will quantify seasonal and intra-urban air temperature differences and provide an independent basis for testing and interpreting the model results.
• Third, the scientific results are converted into planning products. Climate-analysis maps describe thermal conditions and cold-air processes, while daytime and nighttime assessment maps evaluate thermal stress in built-up areas and the climate-ecological importance of green and open spaces. These results are synthesized in a planning guidance map with differentiated priorities for intervention and protection. The underlying geospatial layers, model outputs and assessments are delivered through a GIS-based urban-climate management system for integration into subsequent planning processes.

GEO-NET Umweltconsulting GmbH leads the modelling, scenario analysis and map production. LIST is responsible for local coordination, the stationary network, mobile measurement campaigns, data quality control and validation. A co-design process with national and municipal stakeholders ensures that the planning guidance map is transparent, robust and aligned with operational needs.

Clim-Lux will provide Luxembourg with a coherent national evidence base for heat adaptation, climate-sensitive spatial planning and the protection of local climate functions.

At the institutional level, the project strengthens the capacity of ministries, administrations and municipalities to assess thermal stress and climate-ecological functions using a common high-resolution information data base. The GIS-based format supports continued use in planning and administrative workflows. At the planning and policy level, Clim-Lux identifies present and future heat hotspots, cold-air production areas, ventilation pathways and open spaces with important cooling functions. The planning guidance map translates these findings into priorities for protection, adaptation and the evaluation of development proposals. At the scientific level, physically based modelling at 5-metre resolution is linked with long-term stationary observations and repeated mobile transects, improving the traceability and interpretation of local heat and cold-air dynamics. At the societal and public-health level, the identification of areas with elevated daytime and night-time thermal stress supports targeted measures to reduce heat exposure. At the environmental and economic level, the project indicates where green infrastructure, shading, ventilation and de-sealing measures are most relevant, while identifying areas whose existing cooling functions should be preserved.

By integrating present and future conditions in one analytical framework, Clim-Lux creates continuity with previous climate analyses while substantially increasing spatial detail and strengthening model validation through dedicated field measurements.