4. Conclusion and discussion
The variation patterns of the extreme precipitation and the
contributions of climate change and urbanization in the UAs over the LP
from 1979 to 2018 are analyzed in this study. The results reveal that
the precipitation intensity during the presummer season has decreased in
the southeastern LP and increased in the northwestern LP, and the
variation trends are much more significant in the urban areas than in
the rural areas. Specifically, the
urbanization can aggravate the
decreasing trends of extreme precipitation in Taiyuan and Xi’an UAs
while enhance the increasing trends in Luoyang, Hohhot and Xining UAs.
The number of light rain days is very sensitive to the urbanization,
which decreases in almost all the cities. Although Xining UA has a lower
level of urbanization compared to the other UAs over the LP, the
urbanization effect is also detected in the wetting trend.
The results also display that the climate change is the dominant factor
for the urban precipitation trends, but the urbanization exhibits
different influences in different periods. In the first twenty years,
the urbanization contribution in the urban precipitation is relatively
weak, and the climate change is the primary factor. In the last twenty
years, the urbanization contribution increases dramatically, while the
contribution of climate change is much weaker than that in the first
stage. The urbanization tends to exert negative impacts on the extreme
precipitation indices in Xi’an and Taiyuan UAs and positive effects in
Luoyang, Hohhot and Xining UAs. In addition, the stronger
intensification of extreme precipitation in the urban areas may be
closely connected with the faster increase of surface temperature and
aerosol particles. To further examine the physical processes of the
urbanization effect on the extreme events in the UAs over different
geographical locations and under different climate backgrounds across
the LP, the dynamic experiments based on the Weather Research and
Forecasting model will be performed in our forthcoming studies.
The climate environment of the UAs over the LP is very sensitive and
fragile. Due to the considerable trends of extreme precipitation caused
by the climate change and amplified by the urbanization, urban
disasters, such as urban water shortage and urban waterlogging, are
expected to be further strengthened. Scientific urbanization planning
and construction should attract attention to alleviate the urbanization
consequences, particularly in large cities.
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