Abstract
Solar activity is one of the main external forcing factors driving the Earth’s climate system to change. The snow cover over the Tibetan Plateau is an important physical factor affecting the East Asian climate. At present, insufficient research on the connection between solar activity and snow cover over the Tibetan Plateau has been carried out. Using Solar Radio Flux (SRF), Solar Sunspot Number (SSN), and Total Solar Irradiance (TSI) data, this paper calculated the correlation coefficients with snow indices over the Tibetan Plateau, such as winter and spring snow depth (WSD/SSD) and snow day number (WSDN/SSDN). These snow indices are obtained from the daily gauge snow data in the Tibetan Plateau. Through correlation analyses, it is found that there are significant synchronous or lag correlations between snow indices and solar parameters on multi-time scales. In particular, the Spring Snow Day Number (SSDN) is of significant synchronous or lag correlation with SRF, SSN, and TSI on multi-time scales. It is further found that SSDN over the Tibetan Plateau has more stable positive correlations with SRF by using the 21-year running mean and cross spectrum analyses. Therefore, SSDN can be ascertained to be the most sensitive snow index to the solar activity compared with other snow indices. Moreover, its influence on summer precipitation of China is strongly regulated by solar activity. In high solar activity years (HSAY), the significant correlated area of summer precipitation in China to SSDN is located further north than that in low solar activity years (LSAY). Such impact by solar activity is also remarkable after excluding the impact of ENSO (i.e., El Niño–Southern Oscillation) events. These results provide support for the application of snow indices in summer rainfall prediction in China.
Highlights
The Tibetan Plateau, which is the largest mountain in the world, has an important impact on the global and regional climate, especially East Asian climate
The positive anomaly and negative anomaly present meridional belt distribution. It indicates that much warmer and moister air mass is transported from the Indian Ocean to western China, leading to intensified precipitation over the area
At 850 hPa, there exist two convergent zones in Xinjiang province and south of Hetao area, which correspond to areas with more precipitation in Figure 6B, located at Qinling Mountains and the Daba Mountain area
Summary
The Tibetan Plateau, which is the largest mountain in the world, has an important impact on the global and regional climate, especially East Asian climate. Much attention has been paid to the influence of the Tibetan Plateau on the East Asian summer monsoon and the precipitation on the interannual time scale. The snow cover over the Tibetan Plateau has obvious interdecadal oscillation itself (Wang et al, 2018). The decline of the East Asian summer monsoon in recent decades is thought to be related to the continuous increase of snow amount in the plateau (Zhang et al, 2004). The anomalous interdecadal oscillation of snow cover in spring and winter is closely related to the shift of abnormal spatial rainfall pattern in summer in Eastern China (Zhang et al, 2008; Ding et al, 2009; Zhou et al, 2009; Wu et al, 2010; Zhao et al, 2010). There may be some other external forcing factors that could modulate the correlation relationship between snow and summer precipitation
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