CLOUDS of dense fog shrouded Shanghai early yesterday morning, grounding many flights, as well as forcing expressways and ferry services to close around the city.

The Shanghai Meteorological Bureau issued an orange heavy fog alert, the second highest in the three-scaled system, at 6:44am across the city and soon upgraded it to red, the highest level, in suburban Minhang and Fengxian districts.

Visibility was cut to 40 meters in Minhang District, the bureau said.

Pudong International Airport saw severe delays with no flights able to land or take off until 9:30am.

Around 15,000 passengers on more than 80 international and domestic flights were stranded - the longest delay was more than four hours. Visibility around the airport was down to less than 50 meters, according to airport police.

City airport authorities said nine international flights were diverted to Hongqiao International Airport to land, with another one landing in neighboring Zhejiang Province.

Services gradually returned to normal from 9:43am.

People leaving or entering the city using other modes of transport also had a tough journey due to the fog.

At least nine major expressways across the city were closed to vehicles yesterday morning and did not reopen until 11am.

Ten out of the city's 18 ferry routes along the Huangpu River were canceled and ferries to city's Chongming and Changxing islands also stopped services, which did not resume until the afternoon.

City traffic police enforced speed limits on Changjiang Tunnel and Bridge, another key route to the islands, leading to long queues.

The fog alert was not lifted until 9:55am as the temperature rose.

The weather bureau said the city was experiencing low pressure with little wind and high humidity, which was the main cause of the foggy weather. Visibility was limited to 100 meters in the districts of Minhang, Fengxian, Jiading and Pudong.

More foggy weather may occur intermittently over the next few days due to the arrival of a cold front?to the north of Shanghai, the bureau said.

The weather this week should be fine and dry, however, temperatures will drop several degrees because of the cold front.

The temperatures today will range from a low of 12 degrees Celsius to a high of 18. However, higher winds should make it feel colder than it has done over the past few days.

• yesterday [´jestədi] n.&ad.昨天；前不久 (初中英语单词)
• bureau [´bjuərəu] n.局；编辑部；事务所 (初中英语单词)
• system [´sistəm] n.系统，体系，制度 (初中英语单词)
• international [,intə´næʃənəl] a.国际的，世界的 (初中英语单词)
• severe [si´viə] a.严厉的；苛刻的 (初中英语单词)
• domestic [də´mestik] a.家庭的；本国的 (初中英语单词)
• neighboring [´neibəriŋ] a.邻近的；接壤的 (初中英语单词)
• province [´prɔvins] n.省；领域；范围 (初中英语单词)
• normal [´nɔ:məl] a.正规的 n.正常状态 (初中英语单词)
• transport [træn´spɔ:t] n.运输；流放 (初中英语单词)
• traffic [´træfik] n.交通，运输 (初中英语单词)
• tunnel [´tʌnl] n.隧道 v.挖隧道 (初中英语单词)
• pressure [´preʃə] n.压榨 vt.对...施压力 (初中英语单词)
• arrival [ə´raivəl] n.到达；到达的人(物) (初中英语单词)
• limited [´limitid] a.有限(制)的 (高中英语单词)
• bridge [bridʒ] n.桥(梁)；鼻梁；桥牌 (英语四级单词)
• suburban [sə´bə:bən] a.郊区的 n.郊区居民 (英语六级单词)
• landing [´lændiŋ] n.登陆；降落；楼梯平台 (英语六级单词)
• humidity [hju:´miditi] n.湿气；湿度 (英语六级单词)