Influence of Solar Activity and Large-scale Climate Phenomena on Extreme
Climate and Hydrological Events in an Arid-Semiarid Region of China
Abstract
With a warming climate, solar activity including Sunspot Number (SSN)
and large-scale climate phenomena including EI Niño-Southern Oscillation
(ENSO), Pacific Decadal Oscillation (PDO) and Arctic Oscillation (AO)
have induced changes in climate extremes and changes in the hydrological
cycle in arid-semiarid regions of the world, thus a detailed
investigation of climate variability can play a key role in water
resources management, drought monitoring, ecological restoration and
sustainable development. In this study, we used wavelet coherence (WTC)
based on continuous wavelet transform (CWT) to assess the impacts of
SSN, ENSO, PDO and AO on multiple interacting hydrological processes and
identify the teleconnection patterns and lead-lag relationships between
the four principal modes and changes in extreme temperature and
precipitation events, meteorological drought, and streamflow variability
in Xinjiang, an arid-semiarid region of China. The results indicated
that solar activity and climatic oscillations were viewed as the primary
drivers for periodic variation of extreme temperature events and the
evolution of drought in Xinjiang. For instance, the ENSO positively
affected warm extremes with intermittent coherence in the 2–6-year band
during 1984–2000 and had negative correlations with cold extremes in
the 2–6-year band at the interannual scale. Compared with warm
extremes, variability in cold extremes was much more sensitive to the
activity pattern of AO. It was clear that the coherence of temperature
variables in Xinjiang with PDO was weaker than that with ENSO and AO,
and there was a nonsignificant covariance between PDO and extreme
temperature events. In addition, the WTC spectra showed that
teleconnection factors including solar activity and three large-scale
climate phenomena had significant impacts on annual and monthly drought
evolution, and AO had the strongest influence on annual standardized
precipitation evapotranspiration index (SPEI) values. In general,
compared with SSN, ENSO, PDO and AO all showed clear leading effects on
precipitation extremes variability and annual streamflow variability for
a specific time and frequency, and solar activity’s influences might be
transferred by ENSO to precipitation extremes or streamflow variability
at the 2–7-year band. Overall, the warming and wetting trend in
Xinjiang may be a local manifestation of global multivariate climate
change. Thus, our findings will have important implications for
designing best practice strategies for water resource management and
ecological restoration in similar arid-semiarid basins around the world.