A burst of dusty and sandy air that swept northern China from Friday to Monday affected an area estimated at 29.03 million hectares.
The China Meteorological Administration said most northern regions had been affected by Monday, including the Inner Mongolia autonomous region, Ningxia Hui autonomous region, Xinjiang Uygur autonomous region, Beijing, and the provinces of Gansu, Shaanxi, Shanxi and Hebei.
An Linchang, a senior engineer at the administration, said cold air from Siberia that passed through Mongolia had caused the dusty and sandy weather in China.
"Currently, sand and dust in Mongolia are easily blown up into the air because in spring its vegetation coverage and precipitation have just started to increase and are not able to ward off the wind," he said, adding that, on average, the period from March to May sees 77.5 percent of the sand and dust storms in China.
He said it was difficult to block the storms this year, even with the help of trees planted in the Three-North Shelter Forest Program, which was launched in the 1970s with the aim of improving environmental conditions by creating shelter forests in northern, northwestern and northeastern China.
"Wind has lifted sand and dust to such a high altitude, sometimes a height of several kilometers, that its transmission distance could be very far," he said. "It may even be transported to the Pacific Ocean, or further to the rest of the world."
Peng Yingdeng, a researcher at the Beijing Municipal Research Institute of Environment Protection, said that in addition to natural factors, improper development like poorly managed construction in cities also contributed to the dusty weather.
"In areas where few people live, natural factors mainly cause sand and dust storms," Peng said. "However, in cities, small sources of dusty and sandy air would be due to construction sites that mishandle the land and their materials."
An said major increases in vegetation coverage in cities and surrounding areas would improve the weather, while in sparsely populated areas like grasslands, care should be taken to properly manage mines, another source of dust.
The administration's Bulletin of National Ecological Meteorology 2019 said China had significantly improved its windbreak and sand fixation capabilities since 2000.
It said the proportion of China's land area likely to be affected by fine dust had decreased from 48.1 percent in 2000 to 41.9 percent last year.
The area with low levels of fine dust or that is dust-free increased from 30.3 percent in 2000 to 39.6 percent last year thanks to increased rainfall and proper management of sand sources.