Alert remains as smog continues to shroud north,central China

China's top meteorological authority on Sunday continued to warn of smoggy weather that has battered parts of China for days. The National Meteorological Center (NMC) issued a yellow alert for smog on Sunday morning, the fourth straight day such an alert has been announced. Smog will persist from Sunday morning till Monday morning in Beijing and Tianjin municipalities, as well as parts of Hebei, Shandong, Henan, Shanxi and Shaanxi provinces, the NMC said. The NMC forecast that smog will ease on Thursday when a cold front is expected to bring about wind. China's meteorological disaster alerts are categorized as blue, yellow, orange and red in order of increasing severity.