Beijing has been hidden in dense fog since Tuesday afternoon. Visibility was less than one kilometer Wednesday morning and the heaviest fog so far this winter resulted in the temporary closure of five of the city's eight expressways

By Wednesday, most of northern and southwestern China, Liaoning Province in the northeast and the lower reaches of the Yangtze River were shrouded in mist, according to the Central Meteorological Station (CMS).

A 217,000-square-kilometer mass of fog covered Beijing and Tianjin municipalities, parts of east China's Shandong Province and north China's Hebei Province Tuesday evening, said Yang Keming, a senior engineer with the CMS.

In some of northern, central and eastern areas, the visibility has dropped to 100 to 200 meters with the air quality rapidly deteriorating, Yang said.

He explained that the unusually heavy fog resulted from warm, humid air currents moving in from the Qinghai-Tibet Plateau to hit the relatively cold, windless weather in these regions.

The fog is expected to remain until Saturday, when a cold front should bring snow, rain and strong winds.

The foggy days have further slimmed Beijing's chances of achieving its blue-sky target for the year. The city needs to see 18 days of clear skies and good air quality in December to meet the goal.

(Xinhua News Agency December 2, 2004)