Connectivity of Nocturnal Cold‐Air Flows for Urban Heat Island Mitigation: Introduction of the Cold‐Air Trajectory Calculator KLATra
ABSTRACT Ventilation of cities by local cold‐air flows is an important measure in urban heat island mitigation and climate‐resilient urban planning. We introduce a cold‐air connectivity analysis to identify relevant cold‐air formation areas as well as urban quarters ventilated by cold‐air flows. The...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2025-07-01
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| Series: | Meteorological Applications |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/met.70080 |
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| Summary: | ABSTRACT Ventilation of cities by local cold‐air flows is an important measure in urban heat island mitigation and climate‐resilient urban planning. We introduce a cold‐air connectivity analysis to identify relevant cold‐air formation areas as well as urban quarters ventilated by cold‐air flows. The nocturnal cold‐air flow trajectories are calculated from numerical model simulations using the single‐layer cold‐air drainage model KLAM_21 and the newly developed trajectory calculator KLATra. The German city of Freiburg im Breisgau is chosen to demonstrate the cold‐air connectivity analysis based on trajectories calculated for two 3‐hourly periods during an idealised night. Hydrological catchment boundaries and land use define eight rural cold‐air formation areas as starting points for forward trajectories, whereas administrative urban district boundaries and land use data are used to define five built‐up quarters potentially prone to overheating as starting points for cold‐air backward trajectories. A rate of connectivity is calculated from the ratio of trajectories connecting cold‐air formation areas with overheated urban quarters to the total number of trajectories. The analysis reveals the potential of cold‐air formation areas to ventilate single or multiple urban quarters at connectivity rates up to 82%. The connectivity analysis therefore supports identification and assessment of the relevance of specific cold‐air formation areas for urban heat island mitigation and may serve as a valuable planning tool and data basis for objective decision making. |
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| ISSN: | 1350-4827 1469-8080 |