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Cool city mornings by urban heat

Theeuwes, N. E. ORCID:, Steeneveld, G.-J., Ronda, R. J., Rotach, M. W. and Holtslag, A. A. M. (2015) Cool city mornings by urban heat. Environmental Research Letters, 10 (11). 114022. ISSN 1748-9326

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To link to this item DOI: 10.1088/1748-9326/10/11/114022


The urban heat island effect is a phenomenon observed worldwide, i.e. evening and nocturnal temperatures in cities are usually several degrees higher than in the surrounding countryside. In contrast, cities are sometimes found to be cooler than their rural surroundings in the morning and early afternoon. Here, a general physical explanation for this so-called daytime urban cool island (UCI) effect is presented and validated for the cloud-free days in the BUBBLE campaign in Basel, Switzerland. Simulations with a widely evaluated conceptual atmospheric boundary-layer model coupled to a land-surface model, reveal that the UCI can form due to differences between the early morning mixed-layer depth over the city (deeper) and over the countryside (shallower). The magnitude of the UCI is estimated for various types of urban morphology, categorized by their respective local climate zones.

Item Type:Article
Divisions:No Reading authors. Back catalogue items
ID Code:73258
Publisher:Institute of Physics


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