Abstract:

Snowfall is an important component of hydrological cycle, which could be used as an indicator of regional climate change. Identifying the variations of snowfall and its influencing factors is essential for snow disaster prevention and water resource management. Based on the daily data of the 72 meteorological stations in the south and north of the Qinling Mountains from 1970 to 2020, wet bulb temperature dynamic threshold method and empirical orthogonal function (EOF) were used to investigate the spatiotemporal variations in dominant modes of cold-season (from November in a given year to the following May) snowfall in the south and north of the Qinling Mountains. This study also explored the possible mechanism for the interdecadal change of dominant modes of snowfall. The results are as follows: 1) The contribution of the first two EOF leading vectors of the snowfall anomalies was 70.8% during the cold season in the south and north of the Qinling Mountains. The positive phase of the first leading mode (EOF1) was mainly characterized by positive snowfall anomalies in the whole study area. Spatially, areas with more anomalous snowfall were distributed in the Guanzhong Basin, as well as the eastern Qinling Mountains, the Daba Mountains, and the Hanjiang River Basin. In correspondence to the positive phase of the second leading mode (EOF2), decreased snowfall occurred in the Qinling and Daba Mountains, whereas increased snowfall occurred in the basins. It indicates that the response of snowfall anomalies to climate change was more sensitive in the mountainous areas. 2) For temporal variations, the EOF1 was primarily characterized by a decreasing tendency with inter-annual variation. After the mid-1990s, more years were in the negative phase, which implies less snowfall over the whole region. The EOF2 mainly exhibited decadal variations and a continuous declining pattern of snowfall in the mountainous areas after the mid-1990s. 3) From the perspective of circulation mechanism, the positive phase of the EOF1 was primarily affected by synoptic-scale wave activates in January over the midlatitudes of Europe-Asian continent. The variability of synoptic-scale wave activity was affected by the anomalous low over Siberia, which led to the consistently less anomalies of snowfall in the whole study area. The positive phase of the EOF2 revealed that snowfall anomalies were closely associated with the negative sea surface temperature anomalies in winter over the central and eastern Pacific. The findings highlight that the combined spatial pattern of snowfall anomalies and its circulation mechanism help explore the precursors of snowfall anomalies.

Key words: climate change, snowfall, interdecadal variability, spatiotemporal analysis, south and north of the Qinling Mountains