Air

Different altitudes

Low clouds reach a maximum limit of 1,800 m, while the low limit can even be at ground level. Stratus, nimbostratus, stratocumulus and cumulus clouds belong to this category.
Average clouds are to be found at elevations ranging between 2,000 and 6,000 m. Altostratus and altocumulus clouds (vedi Immagine: nuvole09) belong to this category, but at these heights we often  find clouds that are moving from the lower layers to the higher ones.
High clouds can reach the limit of the troposphere. They consist mainly of ice crystals and not drops of water due to the low temperatures. Cirrus, cirrocumulus and cirrostratus clouds belong to this category.
Clouds as indicators of the weather
The shape of the clouds depends on the process that  formed them, and by the movement of the air within them and in the surrounding zones. Therefore they can be indicators of the meteorological conditions  and can be a valid help in short-term weather forecasts.
When the air is humid and unstable,  generally  cumulus and cumulonimbus  clouds are present, instead, when the air is dry and stable, they tend  to be lenticular. If the air mass lifts slowly and regularly, the clouds that form are generally stratified (vedi Immagine: nubistrato01), if instead, it lifts rapidly, cloud development is prevalently vertical, as in cumulus and cumulonimbus clouds (vedi Immagine: nuvole08).  If the air is very humid and unstable, the air mass is lifted very rapidly and the cloud has a towering shape. The upper part rapidly and constantly changes due to the internal convective movements, but once it reaches the limit of the stratosphere, it flattens like an “anvil” and stops rising, this is the characteristic form of cumulonimbus clouds that are always carriers of precipitation, which may even be rather violent.