Do clouds form exclusively in the troposphere of the atmosphere, or have they ever been found at higher levels?
Clouds typically do not form above the troposphere because of the dryness of those levels of the atmosphere, but there is one type that does form in the stratosphere. This typically occurs in the winter and at high latitudes (typically near Antarctica and the Arctic), and they are called polar stratospheric clouds. Another kind of cloud that forms even higher is called Noctilucent clouds.
