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Strong intensification of hourly rainfall extremes by urbanization
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  • Hayley J Fowler,
  • Yafei Li,
  • Daniel Argüeso,
  • Stephen Blenkinsop,
  • Jason Peter Evans,
  • Geert Lenderink,
  • Xiaodong Yan,
  • Selma de Brito Guerreiro,
  • Elizabeth Lewis,
  • Xiaofeng Li
Hayley J Fowler
Newcastle University

Corresponding Author:hayley.fowler@ncl.ac.uk

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Yafei Li
Beijing Normal University
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Daniel Argüeso
University of New South Wales
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Stephen Blenkinsop
Newcastle University
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Jason Peter Evans
University of New South Wales
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Geert Lenderink
Royal Netherlands Meteorological Institute
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Xiaodong Yan
State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University
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Selma de Brito Guerreiro
Newcastle University
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Elizabeth Lewis
Newcastle University
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Xiaofeng Li
Newcastle University
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Abstract

Although observations and modelling studies show that heavy rainfall is increasing in many regions, how changes will manifest themselves on sub-daily timescales remains highly uncertain. Here, for the first time, we combine observational analysis and high-resolution modelling results to examine changes to extreme rainfall intensities in urbanized Kuala Lumpur, Malaysia. We find that hourly intensities of extreme rainfall have increased by ~35% over the last three decades, nearly three times more than in surrounding rural areas, with daily intensities showing much weaker increases. Our modelling results confirm that the urban heat island effect creates a more unstable atmosphere, increased vertical uplift and moisture convergence. This, combined with weak surface winds in the Tropics, causes intensification of rainfall extremes over the city, with reduced rainfall in the surrounding region.