Journal article
Urbanization Intensifies Heavy Hourly Rainfall Preconditioned by Heatwaves
Journal of geophysical research. Atmospheres, Vol.130(2), e2024JD041184
01/28/2025
DOI: 10.1029/2024JD041184
Abstract
Heatwave preconditioned‐heavy rainfall (HW_HR), a preconditioned compound event, can cause more damage than a single heatwave or rainstorm. Both heatwaves and rainstorms can be exacerbated by the presence of cities, but the response of their compounding to urbanization remains unclear especially at the hourly scale. Here, we investigate the spatial and temporal responses of hourly HW_HR to a typical urban agglomeration, the Pearl River Delta, using observations and scenario‐based numerical simulations. Compared to rural areas, the observations show that HW_HR in urban areas has a higher probability of occurrence and mean intensity, and its diurnal cycle of frequency is narrower, peaking in the afternoon. The temporal and spatial response of HW_HR intensity to urbanization effects is the most significant, with the urbanization‐induced increase in HW_HR being five times that in non‐heatwave preconditioned‐heavy rainfall (noHW_HR). Our simulations support the observations and suggest that urbanization‐induced changes are intense and spatially heterogeneous in HW_HR but relatively weak and spatially continuous in noHW_HR. The simulations also suggest that heatwave preconditioning not only amplifies urbanization‐induced changes in key variables that alter atmospheric conditions but also provides a pre‐storm unstable environment for the urban‐induced warm‐dry surface to trigger and enhance convection. The sub‐daily pre‐storm environment suggests that the preconditioning‐induced thermodynamic changes gradually decrease, whereas the dynamic changes gradually increase as the event approaches. Our study highlights the importance of understanding urbanization effects on preconditioned events, providing new insights into the role of preconditions in the urban water cycle.
Both heatwaves and rainstorms can be exacerbated by urbanization, but the response of heavy rainfall preconditioned by heatwave to urbanization remains unclear especially at the hourly scale. We address this knowledge gap using observations and numerical simulations. We find that the preconditioned events are stronger and more likely to occur in urban than rural areas, and their diurnal cycle is narrower, peaking in the afternoon. Urbanization‐induced increases in the intensity of preconditioned events are significant and much larger than non‐preconditioned events. Our simulations support the observational findings and suggest that urbanization‐induced intensity changes are large and spatially heterogeneous in preconditioned events. The simulations also suggest that heatwave preconditioning not only makes urban areas warmer and drier but also provides a favorable unstable environment for the formation of urban storms. During several hours before the preconditioned events, the preconditioning‐induced changes in heat and moisture gradually decrease, whereas changes in vertical motion gradually increase. Our study points to preconditioned events as a major threat causing rainstorms and flooding within the urban agglomeration and highlights the importance of understanding the urbanization effects on preconditioned events.
Heatwave preconditioning amplifies the role of urbanization on heavy hourly rainfall in the Pearl River Delta, China Heatwave preconditioning provides a pre‐storm unstable environment for the urban‐induced warm‐dry surface to trigger and enhance convection The preconditioning‐induced thermodynamic (dynamic) changes decrease (increase) closer to the peak of the rainfall event
Details
- Title: Subtitle
- Urbanization Intensifies Heavy Hourly Rainfall Preconditioned by Heatwaves
- Creators
- Zifeng Deng - South China University of TechnologyGabriele Villarini - Princeton UniversityZhaoli Wang - South China University of TechnologyXushu Wu - South China University of TechnologyZhaoyang Zeng - South China University of TechnologyChengguang Lai - South China University of Technology
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Atmospheres, Vol.130(2), e2024JD041184
- Publisher
- AMER GEOPHYSICAL UNION
- DOI
- 10.1029/2024JD041184
- ISSN
- 2169-897X
- eISSN
- 2169-8996
- Grant note
- National Key Research and Development Program of China: 2021YFC3001000 National Key R&D Program of China: 52209019, 52379010, U1911204 National Natural Science Foundation of China: 2022A1515240071, 2023B1515020087, 2022A1515010019 Natural Science Foundation of Guangdong ProvinceChina Scholarship Council
The research is financially supported by the National Key R&D Program of China (2021YFC3001000), the National Natural Science Foundation of China (52209019, 52379010, and U1911204), the Natural Science Foundation of Guangdong Province (2022A1515240071, 2023B1515020087, and 2022A1515010019), and the China Scholarship Council. We are thankful to the European Centre for Medium-Range Weather Forecasts for providing ERA-Interim data. The comments by two anonymous reviewers are gratefully acknowledged.
- Language
- English
- Date published
- 01/28/2025
- Academic Unit
- IIHR--Hydroscience and Engineering; Civil and Environmental Engineering
- Record Identifier
- 9984775264502771
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