Combined influence of solar activity and internal climate modes on long-term hydro-climatic variability in the Qinghai-Tibet Plateau

Solar activity and internal climate modes (e.g., ENSO and PDO) have significant effects on extreme climate events and streamflow variability. As the roof of the world and the water tower of Asia, the Qinghai-Tibet Plateau (QTP) is highly sensitive to climate change. Therefore, it is of great significance to study the relationship between extreme hydrometeorological events of the QTP and climate change for global hydroclimate research. In this study, we analyzed the spatiotemporal variation and significant oscillation period of several hydrometeorological variables such as extreme precipitation indices (EPIs), extreme temperature indices (ETIs) and annual runoff based on the observation data of hydrometeorological stations in the QTP during 1962–2019 using Sen’s slope estimator, Mann-Kendall test and continuous wavelet analysis (CWT). And the teleconnection patterns and the leading–lag relationship between solar activity, internal climate modes and these hydrometeorological variables were evaluated using wavelet coherence (WTC). The result showed that QTP has been wetter and warmer in the past 58 years. The EPIs mostly mutated around 2010, and the increase was more pronounced after that; while the ETIs mainly mutated in the late 20th century. In terms of spatial distribution, the EPIs (except consecutive dry days) decreased from southeast to northwest; while distribution of ETIs was much more complicated. The extreme warm and cold indices showed a significant increasing and decreasing trend, respectively. The annual runoff of natural rivers in the QTP showed an increasing trend, and suddenly changed around 2000. EPIs had significant periodicities at 2–4-year band and 4–7-year band, while the significant periodicity of ETIs was mainly concentrated in the 2–4-year band. In addition, the annual runoff of natural rivers had significant periodicities in the bands of 2-4 years, 4-7 years and 7-11 years. Hydrometeorological variables had higher correlations with EI Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) than with sunspot number (SSN). Solar activity first affects internal climate variability and then sequentially transfers this influence to meteorological and hydrological variables. This study has important implications for water resources management, flood control, climate feedback, ecosystem restoration, and the well-being of surrounding residents and sustainable development at the QTP.

Keywords: climate change; extreme climate events; runoff; Qinghai-Tibet Plateau; spatiotemporal variability; wavelet analysis