Influence of solar activity and EI Nino-Southern Oscillation on precipitation extremes, streamflow variability and flooding events in an arid-semiarid region of China

Solar activity including sunspot number (SSN) and EI Nino-Southern Oscillation (ENSO) affect both surface and subsurface hydrological processes in arid-semiarid regions of the world, thus evaluating multi-scale hydrological response to global climate changes can provide valuable information on regional water resources management and ecological restoration. In this study, we utilize wavelet coherence together with continuous wavelet transform to analyze the influence of SSN and ENSO on multiple interacting hydrological processes and distinguish nonstationary patterns in annual precipitation and extreme precipitation events and their effects on short-term or long-term streamflow variations and periodic flooding in Xinjiang, an arid-semiarid region of China. The results indicate that the climate in Xinjiang has become wetter during the period 1960-2019. Extreme precipitation events in Xinjiang have significant oscillation periods at the 2-4 years band, and stations with strong extreme precipitation events are located in northern Xinjiang and Tianshan mountain area, while stations with weak extreme precipitation events are found in southern Xinjiang. The annual precipitation has significant multiple-periodicities at the 2-7-year band, at the 7-11-year band, and at the 13-15-year band. Furthermore, annual streamflow data for nine natural rivers all have significant dominant periodicities at inter-annual scale of 2-4-year and 4-7-year band, and monthly streamflow data for Yarkand river has significant periodicities at intra-annual scale of 3-7-month and 8-14-month band. Since evolution of annual streamflow variability and monthly streamflow variability all show direct response to precipitation features, increasing extreme precipitation events significantly affect streamflow fluctuation of natural rivers in Xinjiang. Overall, SSN and ENSO is viewed as one of the main drivers for annual precipitation or extreme precipitation periodic variation by either enhancing or suppressing convection, and the SSN and ENSO-modulated precipitation anomaly contributes to significant streamflow variation or regional flooding disasters. Investigating the detailed linkage between interannual to multidecadal climate variability and hydrometeorological variables will help decision-makers and scientists to better understand variability in regional hydrological processes, which has great implications for water resources planning and operations in Xinjiang under future climate uncertainty.