我国北方沙尘天气的气候成因分析

Climatic controls of dust storm events in northern China

本研究的范围在30°N以北地区,站点340个。通过采用区域平均及相关分析的方法,将中国北方沙尘(扬沙+沙尘暴)事件的年、季特征及其关系较为密切的地面气象要素包括降水、温度、风(风速、大风日数、风速≥5 m/s的日数)、湿度、蒸发量作了详细、综合的相关、对比分析。结果表明:春季多降水对沙尘天气的发生可以起到明显的抑制作用;前冬至次年春季的气温突变容易诱发沙尘天气的发生;在温度偏高、湿度较大、风力偏弱、蒸发量不大的年份,少沙尘天气;风要素是影响沙尘天气最为直接相关的因子。

The sand-dust weather is a typical disastrous weather,which can be divided into three categories:sandstorm,blowing sand and floating dust.Sand and dust weather usually occurs in the semi-arid,arid and desert area.The formation of dust storms to be three basic conditions:First,high winds.The other is the ground bare sand material.Three are unstable air.Days with sand dust are attributed to the background of large-scale circulations.In addition to this,it is related to climatic factors.In northern China is the world's four major storms District(Central Asia,North America,Africa and Australia),sandstorm zone in Central Asia as part of modern dust storms,which are one of high incidence areas.In this paper,the author analyzed climatological variation of dust storms from 340 observation stations selected in Northern China from 1961 to 2003.By using correlation analysis and regional mean method,,the relationship between the variability features on seasonal and inter-annual scales of tendency of days with dust storms and the influencial factors such as precipition,air temperature,wind,relative humidity,evaporation and so on is analyzed and discussed in detail.The results are observed,that in spring the declining of days with dust storms is obviously related to increasing precipition,dust storm events are more frequent when the temperature has an abrupt change from last winter to next spring,and this is because the spring in northern China,sparse vegetation,desert and bare surface warming rapidly warmer,the ground temperature quickly,then the event of strong cold air transit,it will be easier the formation of sandstorms.The research also shows that Dust storms are more likely to occur in the years when temperature,mean relative humidity is low,mean wind speed is high or days with strong wind are more.And mean wind speed is the most important factor influencing the frequentcy of dust storms in northern China.Once there is strong wind,dust and tiny pieces of sand will be heaved into the air,causing flying dust,flying sand and even sandstorms.