Mechanistic understanding of the summer precipitation and recent wetting
trend over Northwest China and Mongolia
Abstract
The arid region of Northwest China and Mongolia (NCM) receives most of
the precipitation in the summer. The need for a better understanding of
the synoptic-scale mechanism responsible for precipitation formation is
accentuated by the recent wetting trend and its implications for future
hydroclimate change. By conducting a hierarchical clustering analysis on
an observationally-based daily precipitation dataset, we show that there
are three distinct precipitation patterns over NCM, one of which is
associated with strong precipitation over the western part of the region
and another over the eastern part. The corresponding large-scale
circulation anomalies indicate that these strong precipitation events
are triggered by the upper-tropospheric disturbances in the form of
transient Rossby wave packets. Furthermore, the wetting trend is linked
to more frequent strong precipitation events over the eastern NCM,
suggesting that it may have been induced remotely by atmospheric
circulation perturbations.