LAUSR

Abstract The positive trend of global urbanization goes along with the conversion of non-urbanized, e.g. natural or agricultural land surfaces, into urbanized surface types, e.g. impervious surfaces. This generally leads to an increased intensity of the urban heat island and calls for mitigation strategies to ensure thermal comfort of the urban residents. In the present study, we introduce a method to identify, map and asses the efficiency of cold-air paths, which are low-roughness open areas that support cold-air drainage or transport from rural into warmer urban areas. We define that cold-air paths connect cold-air reservoir areas (CARA) with cold-air impact regions (CAIR). The approach combines numerical modelling using the cold-air flow model KLAM_21 with geostatistical analysis using GIS. In our study area Braunschweig (Northern Germany, 250,000 inhabitants) eight cold-air paths of different lengths and surface areas were identified. The identified surface area of cold-air paths varies between 1.7 and 18.0 km2, and the respective cold-air volume between 0.04 and 0.53 km3. The efficiency of cold-air paths was classified according to six criteria taking the size, length, and the cold-air volume and dynamics into account. The method shows promising results, is transferable to other urban areas and offers potential to support decision-making in urban and environmental planning.