High-resolution mapping of urban wet-bulb temperature and its intra-urban variability: A London case study

Wen, Zitong, Zhuo, Lu, Wang, Jiao, Jiang, Zeyi, Zhu, Jingxuan, Zhong, Ming and Han, Dawei 2026. High-resolution mapping of urban wet-bulb temperature and its intra-urban variability: A London case study. International Journal of Applied Earth Observation and Geoinformation 154 , 105649. 10.1016/j.jag.2026.105649

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Abstract

Most extreme-heat studies map high-resolution near-surface dry-bulb air temperature (Ta), yet wet-bulb temperature (Tw) fields that can capture the combined effects of Ta and humidity to represent human heat stress remain limited. This data gap constrains investigation of intra-urban heat variability and the timing of peak heat stress. Here, based on the Rankine-Kirchhoff approximations of Romps, this study innovatively generates hourly 1-km Tw by integrating crowdsourced station observations with remote sensing and reanalysis data in machine learning based downscaling frameworks. Taking London during the summers of 2019–2022 as a case study, the tuned RF-based downscaling approach achieved the best performance (MAE = 0.65 °C, RMSE = 0.93 °C, R2 = 0.91) among all models. The resulting Tw patterns diverge from those commonly reported for Ta: blue infrastructure shows no consistent cooling effect, whereas vegetated areas cool Tw increasingly as tree cover rises, pointing to tree-dominated green infrastructure as a promising humid-heat countermeasure. Results further show that daily maximum Tw occurs 0.7 h earlier than daily maximum Ta in London, opposite to findings elsewhere, implying that climate type and coastal influence modulate the timing of peak Tw, which may affect the attribution of excess nighttime mortality. Besides, a systematic global assessment of the mechanisms controlling Tw extremes is also required in the future.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences Schools > Physical, Chemical & Environmental Sciences
ISSN:	0303-2434
Date of First Compliant Deposit:	3 November 2026
Date of Acceptance:	19 October 2026
Last Modified:	03 Nov 2026 10:45
URI:	https://orca.cardiff.ac.uk/id/eprint/190614

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