The cumulus humilis cloud structures are usually associated and known in meteorological circles as the fair weather clouds. The reason for this is that unlike the other varieties of cumulus structures, the humilis are shorter and have a lower mass. Consequentially, since they develop immediately after the condensation level, they do not grow into other clouds, but rather dissipate in a matter of minutes. The main reasons of their development are the small masses of hot air that rise from the earth's surface during summer. However, it is important to note that sometimes they can collapse into stratocumulus structures and will cover large areas of the sky.
How do cumulus humilis clouds look like?
Even though they maintain the puffed and heap appearance, the humilis clouds are usually more flattened than any other variety of cumulus. In addition unlike the other cumulus types, they tend to have more of a grey tone that is due to the high concentration of water droplets. Because they are the result of a weak convection, as indicated by the humilis taxonomy, which usually implies that they are smaller in size and have a shallow depth. In fact, this is the only cumulus formation that is considered to have a wider base, as correctly pointed out by any ground observer.
What height are the cumulus humilis clouds found?
Since the heat and mass transfer is rather weak compared to the rest of the cumulus varieties, the humilis clouds will usually develop at lower altitudes. On flat terrains and temperate climate countries the humilis starts forming at about five hundred meters above sea level. However, above mountains and in countries with a hot climate, they can start growing at approximately three thousand meters altitude. Regardless of whether they appear alone or with other clouds, they are associated with a clear and sunny weather, making them any aircraft pilot’s dream. However, smaller planes can feel some turbulences when penetrating the cloud.
How are the cumulus humilis clouds formed?
In general, when the fronts of warm air start raising up in the atmosphere the rules of physics indicate they are going to cool down with a certain number of degrees Celsius for each kilometer. However, sometimes, a phenomenon known as temperature inversion can take place. That is exactly the criteria why the convection of the warm air masses are weak and form the small patches of clouds catalogued as cumulus humilis. This is also the explanation for the unusual height of the humilis clouds. While it is true that they tend to dissipate very fast, sometimes they can also contribute to the early development of other cloud varieties such as:
- Cumulus mediocris
- Cumulus congestus
- Cumulonimbus incus
Where can I see cumulus humilis clouds?
Due to the criteria that they require in order to develop, these cloud patterns are widely distributed across the globe, except the polar regions. However, they are more common for summer, when the high temperatures permit the rise of the hot air masses from the oceans and landscapes.