Meteorologists explained that the winter's shortage of precipitation has likely caused the multiple sandstorms that have hit Beijing over the past two months.

According to Science Daily, sandstorms have occurred in Beijing on average 10.3 times per year for the past seven years, which is 4.6 times less than the previous three decades from 1981 to 2010.

However, the first three months this year have seen storms of grit and dust sweeping through Beijing seven times already, creating bewildered reactions as people wonder about the country's efforts to build a "green wall" to the north to combat desertification. Consequent rumors have been spread online, suggesting that the sandstorms were mostly caused by lumbering for the building of the "green wall," also known as the Three-North Shelter Forest.

Peng Yingdeng, research fellow at the National Engineering Research Center for Urban Environment Pollution Control, said, "Forestation is effective to constrain sandstorms, but the 'green wall' alone in the current scale is far from enough."

In the meantime, said Xu Xiangde, an academician from the Chinese Academy of Meteorological Sciences, the protective forests are expected to hold sand, reserve water and counteract wind erosion to reduce the chance of sandstorms.

However, Xu added, the trees, typically 20 to 30 meters high, cannot mitigate the impact of cold fronts and gales, which can blow 1,500 meters above the ground.

Rao Xiaoqin, senior engineer from China Meteorological Administration said the frequent sandstorms this year can mostly be attributed to meteorological conditions in Beijing and the surrounding areas, where rain and snowfall have been exceptionally rare throughout the first few months of this year.

In addition, the defrosted ground cover and frequent cold fronts can also blow sand into air, Rao added.

According to Peng, local governments these days are showing less concern for sandstorms, partly because they are free of taking responsibility for pollution that may originate in other places.

"It is because they take sandstorms as a natural phenomenon, while neglecting the fact that they could be prevented," the meteorologist argued.

A research study conducted by more than 100 scientists over a four-year period has shown that forestation is not only inimical to the control of sandstorms, but will also work to reduce the presence of smaller particles such as PM 2.5 as well.

In Beijing, for example, the woods in its six urban areas combined can hold an annual average of 9,684 tons of air pollutants, including 105 tons of PM 2.5 particles, which could bless the city with 15 additional days per year of good and moderately good air quality.

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