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Impacts of City Shape on Rainfall in Inland and Coastal Environments
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  • Wufan Zhang,
  • Jiachuan Yang,
  • Long Yang,
  • Dev Niyogi
Wufan Zhang
Hong Kong University of Science and Technology
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Jiachuan Yang
The Hong Kong University of Science and Technology

Corresponding Author:[email protected]

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Long Yang
Nanjing University
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Dev Niyogi
The University of Texas
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Urbanization manifests rainfall anomalies both in and around the city. While prior studies have assessed the effect of urban expansion as well as city size, little is known about the impact of city shape on rainfall. Here, idealized large eddy simulations (LES) coupled with the Weather Research and Forecasting (WRF) model are conducted to bridge the knowledge gap. Results indicate difference in the timing for urban-induced rainfall in the inland versus coastal environment. This is associated with contrasting diurnal cycles of vertical velocity and cloud water mixing ratio driven by the land-sea breeze. The impact of city shape on rainfall is more evident in the coastal environment, as buoyancy flows arise from cities alter the interactions between urban-rural circulation and sea breeze. A circular city show nearly 22.0% larger rainfall accumulation and 78.6% greater rainfall intensity compared to a triangular city over urban surfaces. Results highlight the need for considering city shape for coastal urban planning, as a potential adaptation strategy to manage rainfall under future climate. Results indicate that coarser models which represent impervious surface area but not the right shape would have a higher uncertainty in simulating rainfall changes.