北京地区一次强沙尘天气过程的中尺度通量特征

Characteristics of the Mesoscale Fluxes During a Strong Dust Storm Weather Process in Beijing

应用大气所325m铁塔的湍流资料和梯度资料，对2003年3月20-23日影响北京的一次强沙尘天气过程的中尺度通量和湍流通量进行了分析，结果表明：冷空气的影响是从上层开始的。沙尘爆发前，边界层有强逆温存在，动量以中尺度输送为主，湍流很弱。沙尘爆发时，向下的湍流动量通量明显加大。湍流动量通量是沙尘沉降的主要原因，但沙尘爆发前的中尺度过程不能忽略。沙尘爆发前后，感热通量均以小尺度的湍流输送为主，中尺度输送不明显。

Based on the mean field data of wind, temperature and the turbulent field data from Beijing 325 m Meteorological Tower, the characteristics of mesoscale and turbulent fluxes during the strong dust storm weather from 18 to 22 March 2002 are discussed. The results show that the influence of cold front is from the upside to the downside of the Atmospheric Boundary Layer （ABL）. Before the dust storm broke out, there is a strong temperature inversion in ABL, and the mesoscale momentum flux is obviously larger than the turbulent momentum flux. While the dust storm broke out, the minus turbulent momentum flux increased rapidly. The minus turbulent momentum flux is the main factor that results in the dropping of the dust, but the mesoscale process can not be ignored before the dust storm breaking out. Before and while the dust storm breaking out, the turbulent sensible flux is much larger than the mesoscale sensible flux.