北京再发红色预警 机动车单双号限行

China warned residents across a large part of northern China on Friday to prepare for a wave of choking smog arriving over the weekend, the worst of which is expected to over capital Beijing, prompting the city to issue its second ever "red alert".

周五，中国向北方大部分居民发出预警，提醒他们要为应对周末来临的雾霾大潮做好准备。这是北京第二次发布最严重的红色预警信号。

The National Meteorological Centre said the smog would stretch from Xian, home to the Terracotta Warriors, across part of central China, through Beijing and up into Shenyang and Harbin in China's frigid northeast.

国家气象中心报告，雾霾会从兵马俑之都西安蔓延开来，穿过中部一些地区，到达北京；北至沈阳和东北严寒之地哈尔滨。

The air pollution will begin rolling in from about Saturday evening and last until Tuesday, with visibility in the worst affected areas such as Beijing likely to fall to less than one kms (0.6 miles), it said.

气象中心表示，空气污染将从周六傍晚持续到下周四；在北京这样的重灾区，能见度会下降至一公里甚至更小。

In Beijing and parts of Hebei province, which surrounds the capital, the pollution index will probably exceed 500, it said. At levels higher than 300, residents are encouraged to remain indoors, according to government guidelines.

中心还报告，在北京和首都周边的河北地区，污染指数可能会超过500。根据政府的指南，在污染指数超过300的情况下，居民不宜到户外走动。

The Beijing city government issued its first "red alert" last week following criticism that previous bouts of smog had failed to trigger the highest warning level.

之前雾霾肆虐，北京市政府未发布最高预警，由此招致诸多批评。上周，北京市政府终于发布了首次红色预警信号。

A red alert is triggered when the government believes air quality will surpass a level of 200 on an air quality index that measures various pollutants for at least three days. The U.S. government deems a level of more than 200 "very unhealthy".

当政府认为空气质量指数会在三日以上都超过200，就会发布红色预警信号。美国政府认为高于200的空气质量指数是“非常不健康”的。

In Beijing, a red alert means around half the vehicles are removed from the roads with an odd-even license plate system enforced, schools are recommended to close and outdoor construction banned.

在北京，红色预警信号表示政府将执行机动车单双号限行，学校会被建议听课，而户外建筑工地会被禁止作业。