Why are Clouds Different Shapes and Sizes

We explore the elemental factors influencing varying cloud types, and discover what clouds are responsible for specific weather conditions.

Look up into the sky and you’ll notice that clouds shift in shape and size. This is due to there being numerous common types of cloud formation, with each performing a natural role, which is determined by external factors such as altitude, condensation and disposition. These include stratus, cumulus, stratocumulus, altocumulus, cirrus, cirrocumulus and cumulonimbus.

Most cloud formations are produced in environments that are saturated, or where relative humidity is at 100 per cent. Varying mechanisms can activate this process. For example orographic uplift, which occurs as air is forced up due to the physical presence of elevated landmass.

As air rises it cools as a result of adiabatic expansion, at a rate of approximately ten degrees Celsius per every 1,000 metres, until saturation occurs. Stratus clouds, for example, form when minimal upward vertical air currents lift a thin layer of air high, which is enough to initiate the condensation of excess water vapour.

Altocumulus clouds are part of the middle order of formations, appearing greyish with dark patchy areas. Often these clouds precede a cold front, and on a warm humid morning indicate approaching thunderstorm activity.

Altocumulus clouds are often produced due to turbulent updrafts of air, uplifted by terrain barriers such as mountains, composed of super-cooled water, below freezing, which has not yet crystallized around a condensation nucleus.

There are several cloud formations at high altitude. Most notable are cumulonimbus, which form if cumulus congestus clouds continue to grow vertically. Ranging from near ground level up to 50,000 feet, this formation releases huge amounts of energy by condensated water vapour. Lightning, hall and violent tornadoes are associated with cumulonimbus clouds.

During the formation, condensation carries droplets up and down several times before being released and combining to form raindrops. In larger specimens up-currents become severe, splitting raindrops and ice crystals, before re-combining and falling to the ground. This contributes to a build up of electrical charges and the occurrence of lightning.