Localising and quantifying night-time cooling effects from sub-catchments in a mid-European low mountain area

Theoretical and Applied Climatology, vol. 151, pp. 1855–1870

Abstract

Abstract We propose a novel method to analyse and quantify cooling effects provided to a settlement by source areas of nocturnal cold-air drainage. In an interdisciplinary approach, these source areas were defined as hydrological sub-catchments of a complex catchment area in a low mountain range. The cold-air drainage model KLAM_21 was used to exclude the energetic influence of the sub-catchments from the model area by surrounding them with artificial barriers. The outputs of these runs were then compared to a reference run without exclusion to derive the cooling effect of each source area. The results were evaluated at sample points along the main valley and for residential areas of a medium sized city and two smaller settlements. We find that in the complex terrain of the study area, also comparatively remote source areas can have a noticeable cooling effect on the residential neighbourhoods of the target settlements from the middle of the night. The strongest effect however, could be attributed to the sub-catchments in direct vicinity of the target areas. The results at the sample points along the main valley showed that the cooling effect decreased with increasing distance to the sub-catchments and usually gets stronger during the night. The variation in strength of cooling effect between different sub-catchments is likely due to their individual properties such as remoteness, size, terrain, land-cover situation and cold-air exchange with other sub-catchments through overflow effects.

Authors 3

1. Niels Döscher corresponding Aachen Physical Geography and Climatology Institute of Geography

   RWTH Aachen University

   Affiliation as printed

   Physical Geography and Climatology, Institute of Geography, RWTH Aachen University, Aachen, Germany

2. Gunnar Ketzler Aachen Physical Geography and Climatology Institute of Geography

   RWTH Aachen University

   Affiliation as printed

   Physical Geography and Climatology, Institute of Geography, RWTH Aachen University, Aachen, Germany

3. Michael Leuchner Aachen Physical Geography and Climatology Institute of Geography

   RWTH Aachen University

   Affiliation as printed

   Physical Geography and Climatology, Institute of Geography, RWTH Aachen University, Aachen, Germany