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- Title
Contrasting Effects of Urban Land Cover Change and Anthropogenic Heat on Summer Precipitation Over the Yangtze River Delta of China: Analyses From an Atmospheric Moisture Budget Perspective.
- Authors
Ma, Xinyue; Yang, Ben; Dai, Guoqing; Lin, Huijuan; Yang, Xuchao; Qian, Yun; Zhang, Yaocun; Huang, Anning
- Abstract
Both urban land cover (ULC) change and anthropogenic heat (AH) emission are important causes of urban heat island, but their relative contributions to the changes in urban precipitation and the related mechanism remain unclear. Based on numerical simulations utilizing the latest realistic urban fraction and AH data over the Yangtze River Delta urban agglomeration, we found that ULC and AH resulted in nearly opposite effects on precipitation. Various dynamical and thermodynamic processes were involved according to the atmospheric moisture budget analyses. AH increased precipitation particularly during afternoon, and the increases were stronger during heavy precipitation events because of the enhanced moisture convergence effect together with the release of moisture storage previously accumulated in the atmosphere. Differently, ULC reduced mean precipitation mainly due to suppressed evaporation. During weak precipitation events, the suppressed evaporation was largely balanced by the intensified moisture convergence, but during heavy events, ULC caused more pronounced precipitation reduction because the moisture convergence response disappeared and failed to offset the evaporation effect. The relative contributions of different dynamical and thermodynamic processes such as those related to circulation, moisture gradient, and background moisture availability to the temporal variation in the total moisture convergence were further quantified. Overall, our results help better understand the relative roles of different aspects of urbanization on precipitation, and suggest that compared to ULC, reduction in AH emission that is tightly related to the energy consumption structure could be more efficient for mitigating the risk of extreme precipitation. Plain Language Summary: Urban land cover (ULC) change and anthropogenic heat (AH) emission are two main causes of urban heat island, but how they would modify urban precipitation are still unclear. Here, based on numerical simulations utilizing the latest urban fraction and AH data over the Yangtze River Delta urban agglomeration, we found that ULC and AH can result in nearly opposite effects on precipitation. AH increased precipitation via intensifying moisture convergence, which was more pronounced during heavy precipitation events. Differently, ULC caused reduction in the mean precipitation due to the limitation in surface evaporation, but the disappeared moisture convergence response that failed to offset the suppressed evaporation was the main reason for the stronger ULC effect on precipitation during heavy precipitation events. Our findings help better understand the relative roles of different aspects of urbanization on precipitation and provide useful information to support the mitigation of the risk associated with extreme precipitation. Key Points: Urban land cover (ULC) and anthropogenic heat (AH), respectively, decreased and increased precipitation in the Yangtze River DeltaBoth the ULC and AH effects on precipitation were more pronounced during afternoon and during heavy precipitation eventsRelative contributions of various dynamical and thermodynamic processes to the temporal variation of precipitation responses were quantified
- Subjects
CHINA; HUMIDITY; LAND cover; ENERGY budget (Geophysics); CONTRAST effect; URBAN heat islands
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 10, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039430