The default condition is a combination of cumulus and stratus clouds.

默认状态的组合是积云和层云。

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Stratus. These low-lying clouds "can give you a strangely claustrophobic feeling." When a stratus cloud forms at a very low level, it is called fog or mist.

层云。这种低垂的云彩“会让你产生一种奇特的幽闭感。”当层云在很低的水平面形成时，它通常被称作雾气。

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However, after three years of observations of low stratus, cumulus and stratocumulus clouds over land, Anthony Del Genio of NASA's Goddard Institute for Space Studies discovered that when air temperatures were higher, clouds were thinner and thus less capable of reflecting sunlight.

CNN: Clouds' role in global warming studied