Shanghai is expected to see clear skies on Saturday when a rare heavy fog that has blanketed the eastern China city since Monday lifts.

Labeled by local meteorologists as a "disaster", the fog had continued through Friday morning, causing highway closures, flight delays and a suspension of ferry services. However, the dangerous conditions may end with the arrival of a cold front tomorrow.

Visibility in the city was reduced to less than 400 meters when the fog started to spread on Thursday night. In the worst-hit suburban areas it was less than 100 meters, Shen Lifeng, a municipal meteorological station senior engineer, said on Friday.

The lingering fog had forced the Shanghai Meteorological Center to issue six warnings, the first time it had happened in a decade.

On Friday alone, 340 scheduled flights could neither land nor take off and around 60 were cancelled at Pudong International Airport. Expressways linking with neighboring cities Hangzhou and Nanjing were closed for more than four hours.

The fog had also increased cases of respiratory problems among Shanghai citizens.

In Shanghai Ruijin Hospital, the average number of patients suffering from respiratory problems, mostly seniors and children, had increased by 20 percent this week to about 200 per day, said Wan Huanying, head of the hospital's Respiratory Medicine Department.

"With the weather like this, people should stay indoors," she said.

Meteorologist Shen said: "Frequent heavy fog has become a major disaster to Shanghai." He attributed it to global warming.

"Shanghai's winter is getting warmer and warmer, which makes it a hotbed for heavy fog."

Shen said fog usually appeared when the temperature lingered between minus three degrees Celsius to 12 degrees Celsius with little wind. As the temperature in winter kept rising in Shanghai, the city would see more fog in future winters.

(Xinhua News Agency January 11, 2008)