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)