Methods to assess heat exposure: A comparison of fine-scale approaches within the German city of Karlsruhe

- Different methods to assess heat exposure distribution overall show similar results.
- Cross validating regions reveals a high confidence.
- Divergent results occur if method characteristics and urban circumstances differ.
- Without knowledge on the regional characteristics one should use more than one model.

Knowledge on the most exposed areas of a city constitutes an important basis for suitable short and long-term planning. We present and compare three different methods that allow us to assess the potential heat exposure for the smallest administrative spatial units, the quarters, in the German city of Karlsruhe which was repeatedly affected by heat waves in the past. The three methods are based on (1) meteorological station data from the city and its hinterland, (2) a city climate index and (3) remote sensing data. The aim is to answer the question whether different approaches provide different levels of heat exposure. By comparing the three methods we could identify regions by cross validation where the level of heat exposure is highly confident. Regions where one model result deviates from that of another, give interesting insights in the interrelation of features of the method and circumstances in the study area. Regions were all the three models showed different results remained very rare. The results may be relevant for decision-makers who want to implement small-scale measures for heat mitigation but only have limited resources available.