Strong intensification of hourly rainfall extremes by urbanization.
Li, Y., H.J. Fowler, D. Argüeso, S. Blenkinsop, J.P. Evans, G. Lenderink, X. Yan, S.B. Guerreiro, E. Lewis and X.-F. Li
Geophysical Research Letters, 47(14), e2020GL088758, doi: 10.1029/2020GL088758, 2020.
Although observations and modeling 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 modeling 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 3 times more than in
surrounding rural areas, with daily intensities showing much weaker increases. Our modeling 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.
Figure 2. Urban gauges show a more rapid increase in hourly rainfall extremes
than rural ones during the last three decades. Ten‐year rolling averages of the
Q95 of hourly rainfall for (a) each urban station and (b) rural station, and the
mean of the gauges. By Q95, we refer to the mean hourly intensity of the
declustered events above the 0.95 quantile. See Figure 1 in the main text and
Table S1 for locations and other station information. The station IDs are shown
in the legend.
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