青藏高原地表位涡制造对中国东部冬季极端低温雨雪事件的影响研究

Extreme low temperature and icy events in winter have received increasing attention during the past few years owing to the often large loss of human lives and exponentially increasing costs associated with them. The mechanisms behind the extreme events in China have been discussed widely from various perspectives. However, the effect of the Tibetan Plateau (TP) is still an open question. In this study, we attempt to investigate the impacts of the TP on the extreme low temperature and icy events in eastern China from the surface potential vorticity (PV) generation perspective. The spatiotemporal variations of the total extreme low temperature and icy events and those in association with surface PV generation anomaly over the TP are compared to reveal the contribution of the TP to the evolution of the extreme low temperature and icy events. Meanwhile, we try to make clear two questions. One is how the surface PV generation anomaly over the TP induce the occurrence of extreme events. The other is why surface PV generation over the TP change before and during the extreme events. By doing so, a new mechanism for the influence of the TP on the extreme events in eastern China is revealed. Our result may be helpful to improve the prediction of the extreme low temperature and icy events, which are associated with surface PV generation anomaly over the TP. It also provides key scientific support for our adaptation to climate change and sustainable social development.

近年来，冬季极端低温雨雪事件因其经常造成重大人员伤亡和财产损失而引起越来越多的关注。迄今为止，前人已从多个角度对我国冬季极端低温雨雪事件的形成机制进行了分析，但青藏高原在其中的作用较少涉及。本研究拟从地表位涡制造的角度分析青藏高原对我国东部冬季极端低温雨雪事件的影响，通过对比与高原地表位涡制造异常相联系的极端低温雨雪事件和总的极端低温雨雪事件的时空演变特征，分析青藏高原对我国冬季极端低温雨雪事件的相对贡献。同时通过分析与高原地表位涡制造异常相联系的极端低温雨雪事件发生前和持续期内高原地表位涡制造异常的原因及其影响冬季极端低温雨雪事件的物理机制，揭示青藏高原影响我国冬季极端气候事件形成的新机制。借此提高对此类极端低温雨雪事件发生的预知，为应对气候变化、保障社会可持续发展提供科学支撑。

近年来，冬季极端低温雨雪事件因其经常造成重大人员伤亡和财产损失而引起越来越多的关注。本项目探讨了中国冬季极端低温雨雪事件的时空变化特征及其影响因子，从地表位涡制造的角度揭示了青藏高原影响南方极端低温雨雪事件的新机制。取得的主要成果有：1）指出极端低温雨雪事件在全国范围内呈现出减少的趋势，但南北方极端事件的变化趋势和影响因子存在显著差异；2）揭示了年际尺度上，青藏高原地表位涡制造通过影响华南准静止锋的强度进而影响中国南方冬季的温度和降水；3）通过提出位涡重构理论和新垂直速度方程，揭示了天气尺度上高原地表制造的正位涡在地表西风作用下向下游输送所导致的对流层中层位涡平流随高度的变化是引起南方地区极端低温雨雪事件发生的主要原因。上述研究成果为进一步理解中国南方极端低温雨雪事件的变化机理提供了新思路。