2014年南疆西部一次大风天气过程分析

利用常规地面、高空观测资料和NECP逐日4次 1?ｘ 1?网格再分析资料，对2014年5月22日发生在南疆西部地区的一次翻山型大风天气过程的物理机制进行了诊断分析。结果表明：本次大风是高压脊衰退，冷空气沿西北路径爆发产生的大风天气过程；喀什站与乌鲁木齐、塔什干指标站气压差有明显的指示意义：喀什站与乌鲁木齐站气压差由负转正达到 3hPa左右，与塔什干站气压差达到最大-26hPa左右，此时可作为出现全区性大风的参考时间节点，当喀什站与乌鲁木齐站气压差扩大到-15hPa左右，维持稳定，与塔什干气压差减小至-13hPa左右，可作为全区性大风结束的参考时间节点；同时大风出现及结束时间节点在地理上呈现阶梯性变化特征；高空急流、垂直速度圈、变压中心以及冷锋的位置变化相互制约影响；高空急流、垂直环流圈的共同作用是高空动量下传重要动力机制；低层南疆盆地的辐合、帕米尔高原的辐散加剧了南疆盆地上升减压和帕米尔高原中低层的下沉加压，是又一动力强迫机制；中低层300hPa-850hPa较深厚的强冷平流输送，盆地热低压发展是翻山大风形成的热力因子。

An analysis on the causes of a strong windy weather process over west of South-Xinjiang in 2014

The physical?mechanism of the gale weather?process across mountain formation in Kashgar on May 22 was diagnosed and analyzed by using conventional surface observation and NEPC (1?? 1?lat/lon) reanalysis data. The results indicated that the gale was caused by ridge decline and cold air outburst along the Northwest path.Pressue?differences?of?Kashgar,?Urumqi?and?Tashkent?station?had?indicative?significance:?Pressure? differences?of?Kashgar?and?Urumqi?changed?from?negative?to?positive,?reaching?around? 3hPa.?Meanwhile?Pressure?differences?of?Kashgar?and?Tashkent?reached?a?maximum,?about?-26hPa,?and?this?could?be?the?reference?time?node?when?the?district?gale?occurred.?When?pressure?differences of?Kashgar?and?Urumqi?expanded?to?about?-15hPa?and?reduced?to?around?-13hPa?compared?with? Tashkent,?remaining?stable,?this?could?be?the?reference?time?node?when?the?district?gale?ended.Upper?jet-stream, vertical velocity,?variable?pressure center and the?variation?of?space?position in cold front interacted with?each other. The interaction of upper jet-stream and vertical circulation were the vital dynamic mechanism of downward momentum transferring from upper air. Convergence in the low layer of south Xinjiang?Basin and divergence in Pamirs exacerbated the rising decompression in south Xinjiang?Basin and sinking compression in low-middle layer of Pamirs, which was another dynamic mechanism. The transportation of deep and strong cold advection between 300 hPa and 850 hPa and development of thermal low were the thermodynamical factor for the strong wind across mountain formation.