中国雪都阿尔泰山暖区暴雪水汽特征分析

为进一步做好中国雪都阿勒泰山冬季冰雪旅游暴雪预报预警服务，利用阿尔泰山固态降水数据、NCEP/NCAR再分析和GDAS数据，应用天气学诊断和不同水汽分析方法对2021年阿尔泰山区3次暴雪过程环流背景和水汽特征进行分析。结果表明：(1) 3次暴雪过程均为新疆北部典型的暖区暴雪过程。(2)欧拉方法分析表明，该区水汽主要源于大西洋及其沿岸，阿尔泰山西边界为水汽输入，东边界和南边界为水汽输出，中、低层的水汽输入量与暴雪量关系密切，水汽通量散度辐合区位于对流层低层。(3)HYSPLIT(拉格朗日)方法分析表明，水汽源地主要来自北冰洋、欧洲，其次是中亚和加拿大，与上述结论明显不同；对暴雪区综合贡献较大的是对流层低层的水汽。(4)构建了阿尔泰山区暴雪过程水汽贡献模型，700 hPa及以上水汽自源地到达关键区后主要从偏西(西南)路径输入暴雪区，700 hPa以下水汽到达关键区后，在环流合适时主要从东南路径输入暴雪区，但从偏西(西南)和西北路径输入暴雪区的水汽也不容忽视；水汽主要在对流层低层聚集，并辐合抬升。

Analysis of Water Vapor Characteristics of Warm-Sector Snowstorms of Altai Mountains in China

The snow capital of China in the Altai Mountains, which is located in the northernmost part of Altay Prefecture in Xinjiang, experiences many Warm-Sector Snowstorms in winter due to the frequent southward movement of the polar front area. These snowstorm disasters sometimes cause more harm to the national economy and people’s lives than rainstorms, often resulting in huge losses to transportation, animal husbandry, electricity, etc. Meanwhile, in order to improve the service level of ice and snow tourism forecast in Xinjiang, it is necessary to actively explore the characteristics of water vapour during the winter snowstorms in the Altai Mountains. Based on the solid precipitation data and NCEP/NCAR reanalysis data of the Altai Mountains, the circulation background and water vapour characteristics of three snowstorms in the Altai Mountains in 2021 are analysed using synoptic diagnosis and different water vapour analysis methods. The results indicate that: (1) The three snowstorm processes are typical of the warm region of northern Xinjiang. The snowstorms mainly occur in the divergence area on the right side of the southwest (by the west) jet axis at the upper level, the southwest (by the west) frontal area at the bottom of the polar vortex, the convergence area in front of the outlet area of the southwest jet at the lower level, and the overlap zone of the surface decompression and temperature rise. (2) The Euler’s method analysis shows that the water vapour in this area mainly comes from the Atlantic Ocean and its coast. The western boundary of the Altai Mountains is a water vapour input, and the eastern and southern boundaries are water vapour outputs. The water vapour input in the middle and lower layers is closely related to the quantity of snowstorms. The convergence area of water vapour flux divergence is located in the lower troposphere. (3) The HYSPLIT’s (Lagrange) method analysis shows that water vapour mainly come from the Arctic Ocean and Europe, followed by Central Asia and Canada, significantly differing from the above conclusion; the water vapour in the lower troposphere makes a significant contribution to the overall snowstorm area. (4) The contribution model of water vapour for the snowstorm process in the Altai Mountains is constructed. When the water vapour of 700 hPa and above reaches the key area from the source, it mainly enters the snowstorm area from the west (southwest) path. When the water vapour of 700 hPa and below reaches the key area, it primarily enters the snowstorm area from the southeast path when the circulation is appropriate, but the contributions from the west (southwest) and northwest paths cannot be ignored; water vapour mainly accumulates in the lower troposphere and converges and rises.