Specific and localized heat warning system built upon normalized analysis of the UHI for the city of Karlsruhe – Results of GreenLung project

Global climate change is increasingly threatening our life in cities due to intensified heat waves and is thereby stressing the resilience of our cities and our society. Multiple descriptions of action plans (e.g., Sustainable development goals, Sendai framework for Disaster Risk Reduction 2015 – 2030 and Heat-health action plans), reflect the public awareness of these threats with the demand for action. Local administrations must implement long-term but also short-term adaptation measures, to increase the thermal resilience of our cities to protect the urban population, especially the vulnerable group.

This contribution will demonstrate how meteorological observations from traverse measurement campaigns, reflecting the urban heat island effect, can be utilized in the aforementioned action plans.

The observations are comprehensively preprocessed to generalize from prevailing weather conditions to observe the typical, thermal response of the urban morphology for authochtonous weather conditions during heat waves. Absolute values of meteorological conditions are no longer considered, as they are mapped to a relative and normalized scale. A subsequently fitted, Generalized Additive Model, considering the local urban structures (gray and green infrastructure), provides this information spatially for the entire urban area. The spatial prediction can be combined with local risk and protection factors (location of vulnerable facilities (e.g., hospitals, nursing homes, kindergartens) and protective infrastructure (e.g., drinking fountains)) to create a valuable tool for short-term protection of vulnerable and exposed populations during a heat wave.

The short-term adaptation (for days) mainly addresses the people's behavior with respect to heat and is often implemented by information and warning systems. The German Meteorological Service operates a national heat warning system at community level based on the forecasts of the ICON-EU model (~6.5km, < 72h). The official heat warnings are derived from perceived temperature for severe and extreme heat and are statistically related to heat mortality. Based on the previously, generalized results, a specific heat warning system on city level (e.g., city of Karlsruhe) is implemented upon the national heat health warning system. The specific warning system is coupled to the national system and provides small-scale warnings and information for short-term adaptation under consideration of spatially resolved vegetation and urban structures. These warnings provide valuable recommendations of action for vulnerable and exposed people on urban district level in a citizen-oriented manner via the municipal systems.