利用兰州大学半干旱气候与环境观测站边界层铁塔梯度观测、湍流观测和PM10浓度资料,分析一次典型冷锋天气过程兰州大气边界层结构和湍流输送特征及其与PM10浓度的关系。结果表明:冷锋过境前边界层有逆温层出现。随着锋面过境,逆温层完全被破坏、消失,混合层迅速发展,边界层低层温度和湿度垂直梯度变得很小,风速垂直梯度则明显增大;PM10浓度先升后降。冷锋过境时垂直湍流输送强烈,经向和纬向动量均向下输送。动量下传使地表尘沙大量扬起,造成冷锋过境初期颗粒物浓度骤升。
The characteristics of atmospheric boundary layer structure and turbulent flux transport in a cold weather process and their relations with PM10 pollution in Lanzhou on April 19, 2007 were analyzed based on the data of gradient measurements of meteorological tower, turbulent flux measurements and PM10 concentration observed at Semiarid Climate and Environment Observatory of Lanzhou University. The main results revealed that there was a temperature inverse layer before the occurrence of the cold weather process. As the cold front passed by, the temperature inverse layer was broken, and a mixing layer developed quickly. The vertical gradients of air temperature and humidity in the lower boundary layer was sharply decreased, and that of wind speed was significantly increased. The PM10 concentration was increased at first and then decreased. The vertical turbulent transport was very strong when the cold front passed by. The vertical momentum fluxes of meridional and latitudinal velocity were transported downward, and the vertical momentum flux of the meridional velocity was high. The turbulent momentum downward transported, especially the downward momentum flux of meridional velocity, was the main factor which caused the dust blowing and the PM10 pollution at the beginning of the cold weather process.
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