青藏高原东侧我国南方暴雪形成机理研究

The study of the heavy snow in the south part of China, specifically occurred on the eastside of Tibetan Plateau and to the south of Huaihe River has important and realistic significance. Such heavy snow always occurs once every a few years, which is not of small probability, mostly from late January to the beginning of February, that is, before China’s spring festival. Once it happens, it paralyzes traffic, interrupts electric power supply, traps the people on the move and causes disaster to the agriculture. Therefore there is urgent need by the country to reduce the loss due to such disaster. .On the other hand, so far, its scientific study has been very limited. Many scientific problems related to it have yet to be solved. We propose this research project of intensified research on it. The specific contents of the research are as following: (1) The role played by the reasonable match of the high latitude and mid-low latitude synoptic system to the occurrence of the heavy snow events in the south part of China; (2) the role played by the changes of the position, strength and shape of the subtropical up-level jet stream in the formation mechanism of such heavy snow; (3) the environmental parameters which lead to the occurrence of the heavy snow events; (4) the reveal of the occurrence of the heavy snow by numerical simulation and sensitive experiments and dynamic diagnosis..Through the research of the above scientific problems, we hope to set down firm theoretical basis for the prediction and pre-warning of the heavy snow in the south part of China, and provide the scientific ideas predicting the heavy snow events. This will make essential contributions to the reduction and prevention of this kind of disaster.

我国青藏高原东侧淮河以南的南方暴雪研究具有重要的现实价值和科学意义。因为这种暴雪每隔几年总会发生一次，并不属于小概率事件，且多发生在元月下旬到2月初，即临近春节前夕。一旦发生将会造成交通中断、电力中断、外出人员受阻及农作物受灾等状况，国家在该方面有很迫切的减灾需求。另一方面，由于过去研究较少，有很多科学问题也没有解决，所以该方面很值得加强研究。具体研究内容是： （1）高低纬天气系统的合理配置对南方暴雪发生作用的研究；（2）副热带急流位置、强度及形态变化对暴雪形成作用的研究；（3）南方暴雪过程中环境参数的分析研究；（4）暴雪的数值模拟敏感性试验及动力诊断研究。. 通过以上科学问题的研究，以期达到为我国南方暴雪的预警、预报打下坚实的理论基础，并提供科学思路（线索），为该方面的减灾防灾做出实质性贡献。

本项目主要针对与南方暴雪有关的高纬度天气系统、副热带高空急流和环境参数进行了研究，并对暴雪的发生过程进行了敏感性数值模拟和动力诊断研究。.南方暴雪的发生和发展需要几个条件。首先，必须有深厚的阻塞高压系统和高空急流系统，其次在我国南方存在向北的暖湿气流。深厚的阻塞高压在低层形成较强的反气旋，源源不断的将北方的冷空气输送到我国南方。高空急流引起的垂直运动将低层暖湿空气输送到高层，为暴雪的发生提供源源不断的水汽。.对于暴雪过程中环境气象参数的研究发现，由于高空冷空气的侵入，使高空降温明显达到-9℃及以下，所以-9℃可作为流域上游暴雪天气时中层大气温度的变化阈值。.准地转条件的垂直运动方程，在大尺度运动中有较好的应用，而在中、小尺度的运动中辐合辐散运动与旋转运动同等重要，所以我们提出了多效应的新型垂直运动方程，可以较为准确地实现强对流运动中的垂直速度的诊断。.对暴雪的个例进行了数值模拟和动力诊断，发现东亚大槽位于120°E的位置时对南方降雪最有利，而且跟西风有关，西风在20m/s以上的时候才对南方降雪最有利。