Professor Qian Zheng'an of the Cold and Arid Regions Environmental and Engineering Research Institute under the Chinese Academy of Sciences (CAS), has been conducting research on the causes of the sandstorms that have increasingly plagued China for a number of years.
Desertification has continued to increase in the past 50 years and, not surprisingly, the frequency of sandstorms increased from the 1950s through the 1970s. However, Qian found that during the two decades starting in 1980, the number of sandstorms dropped even though the deserts continued to expand. Qian says the reason for the decline was a change in East Asian atmospheric circulation.
From the '50s through the '70s, low-pressure systems frequently appeared in Mongolia in spring. The cold air behind the low-pressure systems always entered northwest China via the northwestern or northern routes, bringing strong winds and causing many sandstorms. Since the beginning of the 1980s, with global warming and the atmospheric environment changing, Mongolia saw more high-pressure systems in spring. The effects of cold air were moderated, resulting in reduced winds and fewer sandstorms.
The situation in the past five years dramatically demonstrates the effects of atmospheric circulation. Sandstorms increased by a factor of eight to ten in 2000 and 2001. In the same period, while high-pressure systems were still predominant in Mongolia, the Sea of Japan area saw more low-pressure systems. This means that cold air entered eastern Mongolia and eastern China from the northeast, bringing many sandstorms to those areas. In 2002 and 2003, weaker low-pressure systems around the Sea of Japan led to a decrease in the number of sandstorms.
(China.org.cn by Zhang Tingting, March 19, 2004)
