Spatial-temporal distribution characteristics of sandstorm weather in Northwest China in recent 55 years | 近55年来中国西北地区沙尘暴发生时空特征分析

صينى. 研究沙尘暴发生的时空变化规律，为制定农业气象灾害预警机制及对策提供依据。以中国西北地区213个气象台站1951-2005年沙尘暴监测资料为依据，统计分析了沙尘暴发生的时空变化规律。陕西、甘肃、青海、宁夏、新疆、内蒙古55年来沙尘暴发生的频次呈逐年上升趋势，尤其是自20世纪90年代后期以来增加趋势明显，其中以甘肃省沙尘暴发生的频次最高；春季（3－5月）是沙尘暴的高发期，其中陕西的80%、甘肃的81.8%、青海的87.5%、宁夏的87.5%、新疆的100%和内蒙古的85.7%均发生在春季，4月是沙尘暴的高发月份，55年来共发生了65次。甘肃、内蒙古、新疆是我国沙尘暴的高发区。西北地区沙尘暴发生具有鲜明的区域及季节特征，每年4月是该地区沙尘暴的高发期。

إنجليزي. Analysis of the laws of the spatial-temporal variation of occurrence of the dust storms is the basis to formulate warning system for agro-meteorological disasters and their countermeasures. Mathematical statistical method was used to analyze the sandstorm monitoring data of 213 meteorological stations in Northwest of China from 1951 to 2005. The results show the frequency of sand storms occurrence is an upward trend since 1951 in Shaanxi, Gansu, Qinghai, Ningxia, Xinjiang, Inner-Mongolia, Gansu, in-particular, had more sandstorms in the late 90s of the 20th century. As for seasonal character, the highest ratio of sand storms occurred was in spring (from March to May), which was 80% in Shaanxi, 81.8% in Gansu, 87.5% in Qinghai, 87.5% in Ningxia, 100% in Xinjiang and 85.7% in Inner Mongolia. Gansu, Xinjiang and Inner Mongolia were more frequently afflicted by dust storms than other areas in China. Results reveal that dust storms happened in Northwest China has distinct regional and seasonal characteristics, and April is the period with the highest frequency of sand storms.