Cumulus Humilis Clouds Essay, Research Paper
The Development and Evolution of Cumulus Humilis Clouds
In order for clouds to form, a few factors are crucial to begin their formation. Clouds, since they are primarily water-based with small amounts of other materials (hygroscopic condensation nuclei), need a ready source of water so evaporation can move the water from a lake or the like, into the atmosphere. Once in the atmosphere, the sun heats the air, causing it to rise, and eventually condense in the colder air, in the higher atmosphere.
The frequency of the Cumulus Humilis cloud to form in the afternoon is due to this heating of the air. As dawn approaches, the air gets cool, since just before dawn is when the air is coldest. As the morning progresses, the sun heats the air and as described before starts.
As the clouds form and begin to grow, they are limited in one direction of growth. The clouds are prevented from downward expansion because of inversion. Inversion is defined to be, An increase in air temperature with height (Essentials of Metrology, 426). The unusually warm air in this region at the cloud base de-condenses, creating a the sharp base of the cumulus humilis clouds.
The top most structure of the cloud is much different. The top of the cloud is puffy because of the rising air. When the cloud tops get very large they are called cumulus congestus , and further vertical development denotes them as cumulonimbus clouds, both also associated with rain showers.
As these cumulus humilis clouds age, the edges of the clouds evaporate, cooling the surrounding air, making it increase in density and fall in altitude. The sinking of the air surrounding the cloud prevents further mixing of the warm and cold air, otherwise known as convection. Because of the air being so still, there is no way for warm air to rise then condense creating another cloud. This is the reason for the large amount of blue sky associated with cumulus humilis clouds.