3 RESULTS
3.1 Trends of precipitation in the
EIB
Figure 2 shows trends in annual precipitation for 2002–2020 and
includes gridded precipitation data from CRU and GPM and observed
station data from CRU. A comparison of sites and grid data showed that
the trends in the observation sites were inconsistent with the CRU grids
in some regions (Figure 2(b)). Among the 112 selected sites, trends for
more than half the sites (60) were inconsistent with those of the CRU
grids. For example, in the mid and downstream regions of the ASB, there
was a non-significant (significance level: p < 0.05)
increasing trend in the annual precipitation of most sites, while the
corresponding CRU grids generally showed a non-significant decreasing
trend. In the Mongolia and Inner Mongolia Plateau, located in the
northeast EIB, there was a non-significant increasing trend in annual
precipitation at most stations, while there was a decreasing trend at
the corresponding CRU grids; this decreasing trend was even significant
for most grids. The trends for most sites were also inconsistent with
the grid results in the northern and western regions of the CSB, with
some exhibiting the opposing trends in these regions.
Trends for the observed sites were highly consistent with those of the
GPM grids in the EIB (Figure 2(a)). In terms of the annual precipitation
trends, the majority of the CRU sites (108/112) were consistent with the
GPM grids. This indicates that the GPM satellite product was highly
reliable in detecting annual precipitation trends in the EIB. Therefore,
the GPM precipitation data were used to analyze the precipitation trends
and simulate the monthly AET series. In general, the annual
precipitation was increasing in most regions, with the exception of the
CSB. The significance of the increasing trend was greater at the
headwater and upstream regions, and the magnitude of the trend was
higher in these regions compared to the mid and downstream regions.
Annual precipitation in most areas of the CSB showed a decreasing trend,
particularly in the Caspian Sea and its adjacent regions. However, an
opposite trend was observed in the northern region of the Volga River
basin.