Divergent Urban Canopy Heat Island Responses to Heatwave Type over the Tibetan Plateau: A Case Study of Xining

Guoxin Chen, Xiaofan Lu, Qiong Li, Siqi Zhang and Suonam Kealdrup Tysa ()
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Guoxin Chen: State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining 810016, China
Xiaofan Lu: State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining 810016, China
Qiong Li: School of Geological Engineering, Qinghai University, Xining 810016, China
Siqi Zhang: Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China
Suonam Kealdrup Tysa: State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining 810016, China

Land, 2025, vol. 14, issue 10, 1-15

Abstract: The escalating heatwave risks over the Tibetan Plateau (TP) highlight unresolved gaps in understanding multitype mechanisms and diurnal urban canopy heat island (UCHI) responses. Using Xining’s high-density observational network (2018–2023) and by employing comparative analysis (urban–rural, heatwave versus non-heatwave days) and composite analysis, we found: During the record-breaking July 2022 heatwave across the TP, Xining reached an extreme UCHI peak (z-score: 3.0). Critically asymmetric UCHI responses as daytime heatwaves amplify mean intensity by 0.35 °C via extreme value shifts, whereas nighttime events suppress it by 0.31 °C. Crucially, heatwaves induce negligible daytime UCHI modulation but drive comparable magnitude nighttime UCHI intensification (during daytime events) and reduction (during nighttime events), demonstrating type-dependent and diurnally asymmetric urban thermal sensitivities. Heatwaves driven by distinct synoptic patterns; daytime events are controlled by an anomaly anticyclone (cloudless, dry conditions), while nighttime events occur under plateau-north anticyclones (cloudy, humid conditions). These patterns fundamentally reshape heatwave–UCHI interactions through divergent mechanisms: Daytime/nighttime heatwaves amplify/suppress nocturnal UCHI through enhanced/reduced urban heat storage and accelerated/inhibited rural radiative cooling. Our case study demonstrates that although heatwaves generally amplify nocturnal UCHI, in dry regions, their synoptic drivers significantly modify this nighttime synergy. The nocturnal UCHI during heatwave is not only driven by humidity effects but also modulated by cloud cover-regulated rural radiative cooling and urban thermal storage. These findings establish a mechanistic framework for heatwaves–UCHI interactions and provide actionable insights for heat-resilient planning in high-altitude arid cities.

Keywords: heatwave; urban canopy heat island; diurnal variation; Tibetan Plateau (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2025
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