Study Of The Characteristics And Formation Of Sand-dust Weather Of Qingdao Area

According to the definition of Meteorological Observing Criterion, Sand-dust weather is classified as floating dust, blowing sand, sandstorms and strong sandstorms 4 categories. Sand-dust weather has been existing since the old time, it has the chronology characteristics. Sand-dust weather was paid much attention again since 21th century since sandstorms happened more frequently, more early and persisted more longly than before. Sandstorms from arid and semi-arid areas not only has strong influence on the local environment but also has impact on the atmospheric environment of the downwind areas.Spatial and temporal characteristics of sand-dust weather in Qingdao area was analyzed based on meteorology observations in 7 meteorological stations from 1961 to 2004. Statistics show that floating dust weahter is the dominating categories,and then blowing sand, sandstorm was seldom to be observed. Comparatively, for the floating dust weather, there was more in 1960-1970s, less in 1980-1990s. But the days of floating dust weather suddenly increased since the end of 1990s, and arrived the maximum untill 2002. Most sand-duat weather happened in Spring seasons, especially in April in Qingdao. From the spatial distribution, there were more sand-dust weather days in the west part ( Jiaonan, Jiaozhou) than the east( Laoshan), which may be caused by the source of the sand-dust and the air humidity.According to the origin of sand-dust, sand-dust weather in Qingdao region can be classified into three types: drifting from other region, origining in the local and strengthening after drifting, in which the first type is the most happened. There were there routes of sand-dust drifting from other regions to arrive in Qingdao: The north, northwest and the west, belong of them the northwest routine was dominated. Sand-dust from the north route was outbreaked in Mongolia, passed through Ke Er Qing Sand-land, Liaodong peninsula to Qingdao. Sand-dust from the northwest route was originated from Mongolia or the desert in the west of inner Mongolia, passedeastward through Loess plateau, Jian to Qingdao. Sand-dust from the west route was transported through Xinjiang, Gansu and Hetao region.The sand-dust weather was closely related with the general circulation of upper air. At the 500hPa altitude, there was a steady deep pressure trough along the east coastal area in the east of Asia, and a steady high pressure ridge in the west of Asia. North of China was controlled by the northwest flow between the ridge and the trough. The strong northwest flow transport cold air from the Novaja Zeml's to the downwind southeast area. This circulation pattern is very typical for the sand-dust weather of north China, Gn the ground, Mongolia cyclone was generated and moved eastward, cold air travelling with the clod front in the south of the cyclone caused huge winds in the surface and the sand-dust weather.The non-hydrostatic mesoscale model MM5 was adopted to simulate the sand-dust weather in March 18-22, 2002. The outbreaking time, persisting processes and moving routes were explained with the modelled surface wind field, vertical wind velocities, etc. It is shown that MM5 can simulate well the strong cyclone weather, the sandstorm's forecasting may be made with the help of it.