Cumulus clouds have noticeable vertical development and clearly defined edges. They are often described as puffy or cotton-like in appearance. They can be alone, come in lines, or in clusters. These clouds are often seen just ahead of other types of clouds like cumulonimbus. This happens when they are influenced by weather factors like instability, moisture, or temperature gradient. These clouds belong to the larger family of cumuliform clouds. This group also includes cumulus congestus, cumulonimbus, and several others. The most intense cumulus type clouds can be associated with severe weather like hail, waterspouts, and tornadoes.
The height where these clouds start to form depends on the amount of moisture in the air parcel that forms the cloud. Humid air generally results in a lower cloud base. In temperate areas, the base of the cumulus clouds is usually up to 2,400 m in altitude. In arid and mountainous areas, the cloud base can be in excess of 6,000 m. Glider pilots tend to look for areas of cumulus cloud formation. They are a sign of rising thermals that will extend a glider pilot’s time in the air. As these clouds evolve into cumulonimbus, pilots can get a little forewarning of impending bad weather and land their aircraft.
Cumulus will form when warm air rises and meets cooler air and the moisture in the air condenses. As it rises, the air cools at approximately 3°C per 100m, while the dew point of the air falls by 0.5°C per 100m. When the temperature of the air reaches the dew point, some water condenses out of the air to form the cloud. The size of the cloud depends on the temperature profile of the atmosphere and the presence of any inversion. When the top of the cumulus cloud reaches to where the temperature is at or below the freezing level; precipitation from the cloud is possible. The temperature of the air at ground level will determine if this falls as rain or snow.
Here on Universe Today we have two great articles about clouds: one is about how clouds are formed and the other is about clouds on Titan. Here is the NASA webpage about how clouds are formed.
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