In winter, there is a dense smog layer over Lanzhou city.

冬季兰州城市上空形成浓厚的烟雾层。

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The existence of the smog layer increases the stability of the urban boundary layer.

烟雾层的存在增加了城市边界层的稳定性。

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The average optical parameters of the urban smog layer over Lanzhou are calculated by using the solar observation data on the two different levels.

利用一次外场试验中两个不同高度上的太阳辐射观测资料，计算了城市烟雾层大气平均光学特性参数。

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Southern California's seasonal "June gloom" weather, caused by a marine layer that traps smog over the Los Angeles basin, will probably pay an extended visit this year.

CNN: Western U.S. to get smoggy summer, fall

The cold waters mean a large temperature contrast between the land and ocean -- conditions that favor the formation of a strong inversion layer that traps smog over cities, such as the Los Angeles, Calif.

CNN: Western U.S. to get smoggy summer, fall