< p >扩展@Poutnik无形的河流类比,冷空气也可以在小池的下降。< / p > < p >在清晰的夜晚,温度波动很频繁的发生是由于辐射冷却。如果空气冷却足够达到露点,云可以作为示踪剂的气穴。< / p > < p >的一个例子是雾补丁,你可能在某些情况下通过。雾补丁的空气有点冷(或更高的绝对湿度,例如在一个湖)比周围fog-free地区。即使不够冷的空气形成云,同样的温度变化可能发生无形。< / p > < p >这里有一个例子从< a href = " https://commons.wikimedia.org/wiki/File: Morning_fog_over_Keravanjoki_river_in_Vantaa _Finland, _2021_October_ -_4.jpg”rel = " noreferrer " >维基用户单Rasanen < / >: < a href = " https://i.stack.imgur.com/FPRUI.png " rel = " noreferrer " > < img src = " https://i.stack.imgur.com/FPRUI.png " alt = "辐射雾早上在平坦的田野和池塘”/ > < / > < / p > < p >在山里,冷的看不见的河流,下行空气@Poutnik提到有时会被示踪云山坡向下流动。寒冷的空气的密度比周围的空气,摩擦小,重力将其拉下来。比相邻地区云将冷无云区。这种效应会导致强烈的下坡< a href = " https://en.wikipedia.org/wiki/Katabatic_wind " rel = " noreferrer " > < / >下吹的风。在南极洲这效果负责一些世界上最强的风。 Here's a good example from Wikimedia user Andrew J. Kurbiko: 
To summarise, the key to the effect you noticed is almost certainly radiative cooling and the movement of colder denser air. Radiative cooling occurs due to any object above absolute zero giving off radiation. On a clear night this radiation passes through the Earth's atmosphere and is lost into space. This cools down the object (land) that the radiation came from. The land, in turn, cools down the air above it. On a cloudy night, the radiation is reflected by the clouds and reabsorbed by the land keeping the temperature constant.
.jpg){kind=link}