| Dust storms are the most common natural disaster in the deserts of northern China and surrounding areas. These storms have dire effects on the environment and production, social activities and human health. The deserts of China are widespread in arid and semiarid regions, each year, a large quantity of sand and dust is entrained from northwest arid area of China and transported to downwind regions by the westerly winds and winter monsoon. This dust not only can reach the whole North China and even to the region South of 23.5 ° N, but also causes widespread contamination by blowing sand and dust throughout all of North China, the Korean Peninsula, Japan, and northern Pacific Ocean. On occasion, this contamination can even reach North America, Europe and Arctic. Therefore, to reinforce research on dust storm in the arid North China is of great importance for East Asia and global environmental change. This study takes the 10 provinces (autonomous regions) which is populated the deserts as the study area. Based on dust storm records and meteorological data from 118 stations in the study area over the period 1960-2007, the diurnal, monthly and interannual variation of dust storms, as well as their relation to wind speed, precipitation, temperature and NDVI, are analyzed and discussed. The main conclusions can be drawn as follows:(1) The distribution of dust source area accounts with that of the desertification lands, the Badain Juran desert, the Tengger Desert, the Mu Us Sandy Land and the Otindag sandy land are significant source of dust storms in the study area. Over time, the source area of dust storm is different. The the Badain Juran desert was always the first dust source area from 1960 to 2007. The dust storm is frequent in Kubuqi desert, Ulanbuh Desert and Mu Us Sandy Land in the year of 1960-1990, the Otindag sandy land became the second in 2000-2007.(2) DSF in the North China area showed a decreasing trend between 1960 and 2007, The decadal variation of DSF during the past 48 years indicates that the highest frequency of dust storms was in the 1960s and the lowest frequency in the 1990s, there was a bit of increasing over the period 2000-2007. Statistical analyses demonstrate that such storms occur more frequently from 9:00 to 21:00 local standard time and much more frequently between March and May, especially April. The duration of dust storms in the study area were mainly 0-6 h and the average duration were 3.4h.(3) The DSF had close relationship with meteorological factors. Although the greatest dust emissions did not appear in regions of highest wind spread(average wind speed, maximum wind speed), there was a positive correlation between wind speed and DSF. Except the Otindag sandy land, the strong positive correlation between wind speed and DSF can be found in most area. Winds, especially strong ones with speeds 10-20 m/s, are the main factor controlling dust storm. The relationship between temperature and dust storms is relatively complex, there was a negative correlation between temperature and DSF beside the Otindag sandy land. Temperature have an indirect effect on DSF by controlling vegetation growth. The dust storm mainly occurred in the area with precipitation less than 450mm, the relationship between precipitation and DSF is not obvious. The precipitation and temperature make effect on the occurrence of dust storm by change the vegetation. |
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