Abstract:

Based on the routine observation data of monthly gale and sandstorm from 17 meteorological stations in the west of southern Xinjiang during 1961-2015 and the NECP reanalysis data with 1°×1° spatial resolution, the variation characteristics of the days of gale and sandstorms in the west of southern Xinjiang were analyzed. The cause and forecast focus of a rare gale on 27 December 2017 were explored. The results show that the gale and sandstorm days in the west of southern Xinjiang decreased in the past 55 years, and significant reduction mutations occurred around 1987. In spring and summer, gales and sandstorms accurred more frequently in western Xinjiang, while in autumn and winter gales and sandstorms occurred less. The case analysis shows that the eastward movement of the European high-pressure ridges promoted the rapid eastward movement of the low-trough over western Siberia and guided the southeast outbreak of the polar cold air, which was the main weather background for this gale event. Drastically warming up, decompression and drought were the pre-weather conditions which were conducive to gale-dust weather. The “foehn effect”, the anomalous warming of the ground caused by solar radiation in the afternoon were the thermal condition of gale-dust weather. The ground wind shear and mesoscale low pressure were the trigger mechanism of sandstorms. The high altitude front zone, the momentum downcast, the low trough deepening associated with the supplement of the polar cold air and the pressure gradient force were closely related to strong winds in the west of southern Xinjiang, and it needed to be paid attention to in winter wind forecast. Under the condition that the dynamic factor was satisfied, the thermal factor was a sensitive factor for sandstorm forecast. The cold underlying surface and the inversion layer can inhibit the occurrence of dust weather.

Key words: west of southern Xinjiang, gale, sandstorm

摘要：

利用南疆西部17个气象站1961—2015年逐月大风沙尘暴常规观测资料和NECP逐日4次1°×1°再分析资料，分析南疆西部大风、沙尘暴日数变化特征，探讨2017年12月27日的一次罕见大风天气成因和预报着眼点。结果表明：近55 a南疆西部大风、沙尘暴日数呈减少趋势，并于1987年前后发生了显著减少性突变。春、夏季是南疆西部大风、沙尘暴的高发季节，而秋、冬季大风、沙尘暴较少发生。个例分析表明，欧洲高压脊东移推动西西伯利亚低槽快速东移引导极地冷空气东南爆发是这次大风的主要天气背景。剧烈升温、减压及干旱是利于大风、沙尘暴的前期天气条件；“焚风效应”、午后太阳辐射导致的地面异常升温是大风、沙尘天气发生的热力条件；地面风切变和中尺度低压是沙尘暴的触发机制。高空锋区、动量下传、低槽加深相联系的极地冷空气的补充及气压梯度力大小与南疆西部翻山大风密切相关，需要在冬季大风预报中重点关注。动力因子满足的条件下，热力因子是判断冬季能否出现沙尘暴的敏感因子，冷的下垫面和逆温层对沙尘天气的发生起抑制作用。

关键词: 南疆西部, 大风, 沙尘暴