Abstract:

It is of great significance to study the climatic characteristics of heavy snowfall in winter over the Qinghai-Tibet Plateau for winter precipitation prediction and snow disaster prevention in the Qinghai-Tibetan Plateau. Based on the daily precipitation data from 99 meteorological observation stations in the Qinghai-Tibetan Plateau in winter (from November to February of the following year) during 1961-2021, the spatial distribution and temporal variation characteristics of heavy snowfall and heavy snowfall days in early and late winter over the Qinghai-Tibetan Plateau and their relationship with sea surface temperature (SST) in different basins and Arctic oscillation (AO) were analyzed by using linear tendency estimation, correlation analysis and ensemble empirical mode decomposition methods. The results show that there were more snowfall processes with larger magnitude in early winter, while snowfall in late winter were more frequent and lasted longer duration in the Qinghai-Tibetan Plateau during 1961-2021. Both heavy snowfall and heavy snowfall days in early winter showed a "less-more-less-more" variation, while heavy snowfall and heavy snowfall days showed a significant increasing trend in late winter. The contribution rate of heavy snowfall and heavy snowfall days in early winter was significantly greater than that in late winter. The central and eastern parts of the plateau are areas with high value of heavy snowfall in early and late winter, and heavy snowfall in the northeast side was also large in early winter. The sea surface temperature anomalies in the tropical Indian Ocean, the north Atlantic Ocean and the Pacific Ocean were important factors affecting heavy snowfall in winter in the Qinghai-Tibetan Plateau. There was a significant positive correlation between heavy snowfall in early winter and SST in tropical middle-east Pacific Ocean and the western tropical Indian Ocean, while the positive correlation between heavy snowfall in late winter and SST in the tropical Indian Ocean, the northwestern Pacific Ocean and the north Atlantic Ocean was the most significant. Since the mid-1990s, the Indian Ocean dipole has changed from a weak positive correlation to a significant positive correlation with heavy snowfall in early winter, and the Arctic oscillation anomaly has an important impact on heavy snowfall in late winter, and both have always shown a stable positive correlation.

Key words: the Qinghai-Tibetan Plateau, heavy snowfall, the Arctic Oscillation, the Indian Ocean dipole

摘要：

研究青藏高原冬季强降雪的气候特征对高原冬季降水预测及雪灾防御有重要意义。基于1961—2021年冬季（11月至次年2月）青藏高原99个地面气象观测站的逐日降雪资料，采用线性倾向估计、相关性分析、集合经验模态分解等方法，揭示青藏高原前、后冬强降雪时空分布特征，对比分析前、后冬强降雪量和强降雪日数差异性，探讨不同海盆海表温度、北极涛动与前、后冬强降雪量和强降雪日数的关系。结果表明：近61 a来，青藏高原前冬初期最易出现较大量级降雪过程，而后冬降雪过程多且持续时间长；前冬高原强降雪量、强降雪日数总体呈“少—多—少—多”变化特征，后冬强降雪量和强降雪日数均呈显著增加趋势；前冬强降雪量和强降雪日数的贡献率明显大于后冬；前、后冬高原中东部主体为强降雪高值区，前冬东北侧强降雪量也较大。热带印度洋、北大西洋、太平洋海表温度异常是影响青藏高原冬季强降雪的重要因子，前冬强降雪量与热带中东太平洋、热带印度洋西部海表温度呈显著正相关，后冬强降雪量与热带印度洋、西北太平洋、北大西洋海表温度的正相关最显著；自20世纪90年代中期开始印度洋偶极子与前冬强降雪量由弱正相关转为显著正相关并维持至今，北极涛动异常对后冬强降雪具有重要影响，二者始终呈稳定正相关性。

关键词: 青藏高原, 强降雪, 北极涛动, 印度洋偶极子