Water vapour condenses to form clouds.

水蒸汽冷凝形成云。

《柯林斯英汉双解大词典》

It would be better if there were some way to see atmospheric water while it is still vapour, before raindrops form.

如果我们能找到一些能在雨滴形成以前的蒸汽状态下就观察到大气水方法，情况会变的好一些。

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Water vapour condenses to form thousands of tiny water droplets which scatter light.

水蒸气冷凝形成无数的小水滴，使光线发生散射。

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Much of it resulted from volcanoes blasting out gases like carbon dioxide and water vapour, which allowed ice (also a mineral) to form near the poles of Earth, and possibly on Mars too.

ECONOMIST: Minerals

Since rising air causes clouds to form (the risen air eventually cools to the temperature of its elevated surroundings, and any water vapour it contains thus condenses), the result would be more rain than would fall in the absence of the artificial aerosols.

ECONOMIST: Saturday-night showers