民勤一次沙尘暴天气过程的近地层气象要素多尺度特征

Multiscale Meteorological Characteristics during a Sandstorm in Minqin

利用民勤站近地层观测资料,对2007年3月27日一次沙尘暴过程中近地层气象要素的多尺度特征进行分析,得到如下结论：（1）在沙尘暴发生期间,民勤站近地层要素存在明显的多尺度特征,其中风速存在约2. 5 h和1 h左右的2个周期,PM（10）浓度存在约为1. 5 h的主周期,20 m高度处扰动气温的主周期与近地层风速的主周期相同,相对湿度不存在小于3. 5 h的主周期。（2）与2. 5 h左右尺度的风速信号相比,1 h左右尺度的风速信号提前3 h出现,这意味着沙尘暴发生发展期间近地层风速存在明显的逆尺度发展特征;与近地层风速和PM（10）浓度信号相比,1 h左右尺度的扰动气温信号提前出现,并在沙尘暴出现阶段逐渐减弱。（3）在沙尘暴出现阶段,近地层风速与PM（10）浓度信号呈同位相变化,而与气温扰动信号存在明显的位相差,这可能意味着沙尘暴发生时重力波的发展对起沙过程起到重要作用。

The multiscale meteorological characteristics during a strong sandstorm in Minqin on 27 March,2007 were analyzed using the data from Minqin Meteorological Station. The results were as follows：（1） It was obvious that the development of meteorological elements was characterized by the multiscale variations in surface layer during the strong sandstorm. Specifically,there were two main periods of wind speed near the surface,and they were for 2. 5 hours and 1 hour respectively,which was the same as the disturbed temperature at 20 m height. Different from wind speed and disturbed temperature,the period of PM（10） concentration was for 1. 5 hours,and there was a period of relative humidity longer than 3. 5 hours;（2） Wind speed signal on a scale about 1 hour occurred 3 hours earlier than that on a scale about 2. 5 hours,which revealed that an adverse scale development of wind speed was apparent during the sandstorm. Compared with the signals of wind speed and PM（10） concentration,the perturbed temperature signal on a scale about 1 hour emerged earlier and its intensity reduced when the sandstorm occurred;（3） It was found that the wind speed signal varied synchronously with the change of PM（10） concentration signal during the sandstorm,however,its variation over the time was not synchronous with the disturbed temperature signal,which probably meant that the development of gravitational wave played a critical role in sand raising.