727. There was temperature inversion when we descended through 3000 feet.
727. 当我们下降 3000 英尺时出现逆温。
TED-Ed(视频版)
That's also partially due to a phenomenon known as temperature inversion, where instead of warm air continuously rising upward, a pollution-filled layer of air remains trapped near the Earth's surface by a slightly warmer layer above.
In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to a "temperature inversion", i.e. an increase in temperature with height, or to the layer ("inversion layer") within which such an increase occurs.