November 20, 2015

Clouds

Welcome to SeeCloud cloud information page! On this page we have collected information on cloud generation, cloud types and properties.

This page is quick tutorial on different clouds to get you started. The web is filled with detailed information on clouds and the processes forming and transforming them. Links to some of the most popular sites have been listed on the bottom of the page.

The air we breathe contains water vapor. Air can contain very little water vapor, like in the deserts of Sahara, or it can be saturated with it, like a Finnish sauna. Water vapor is also the stuff clouds are made of.

Clouds are formed typically when air is saturated with water vapor. In other words the relative humidity of air reaches 100%, and the dew point temperature equals air temperature. This simply means that the air contains as much water as it can and if by some process more water is added, it will drop off. The shedding of extra water is called rain (or in fancier terms, precipitation) or condensation.

Different cloud types have very different properties. A typical high-altitude cloud shows as white wisps way up in the sky and does not prevent the warming radiation of sun from reaching the earth, whereas a thick precipitation producing cloud might cover half a continent and can stay in one place for days. Clouds do have a major effect on the perceived weather, therefore it is no wonder that they are also an important research topic for meteorologists.

Cloud Types, image from wikipedia.

Cloud family classification based on altitude by Valentin de Bruyn .

Modern day meteorology has divided clouds into ten different main classes or genus, which are then divided into sub classes or species. The classes have fancy sounding latin names, but don’t let that turn you off. There is logic behind the names and soon you can impress your friends by pointing out the a cloud and describe it’s species in scientific sounding terms!

A common cloud categorization is done in the basis of their height. High altitude clouds belong to cirriform family. The word cirriform is derived from latin word cirrus, which means a curl or a tuft, and this is a rather accurate description of their appearance. Cirriform clouds have altitude ranging between 5000 meters and 12,000 meters (16,500 ft to 40,000 ft).

Cirriform clouds have been divided into three classes:

  • Cirrus clouds
  • Cirrocumulus clouds
  • Cirrostatus clouds

Note the postfixes of the two latter classes: cumulus and stratus. We will come back to these later.

The next cloud genus, when descending from cirriform height, is called alto clouds. Alto is latin and means high. Despite the name, clouds in the altofamily are not highest clouds and usually the base of the cloud is ranging from 2,000 to 6,000 meters (6,000 ft to 18,000ft).

Like cirriform clouds, altoclouds are also divided into three classes:

  • Altocumulus clouds
  • Altostratus clouds
  • Nimbostratus clouds

The two new latin words found in the cirriform clouds are also present here, cumulus and stratus. They both refer to the shape of the cloud. Cumulus is latin and means puffy; cumulus cloud is a common sunny day cloud and is often considered as the archetype of a cloud. Try searching for cloud in google image search and you will get a cumulus cloud.

Stratus is also latin and means stretched or spread out. Stratus clouds often cover the whole sky and usually in the lower levers will produce light or heavy rain.

The third cloud type in altofamily is the nimbostratus cloud. Nimbo (or actually nimbus) simply means rain in latin, so we have a spread out cloud covering the whole sky producing rain. A very common cloud for British Isles.

The lowest of the cloud genus are simply called low clouds (no fancy latin words here). The genus contains three classes whose properties may be pretty self-evident by now:

  • Cumulus clouds
  • Stratocumulus clouds
  • Stratus clouds

Cumulus clouds are small, white and puffy and are usually produced on a warm sunny day. Stratocumulus clouds are often generated from multiple cumulus’: when the process that generates cumulus clouds keeps on producing them, the clouds slowly fill the sky so that the clear sky between distinct cumulus clouds gets very small.

Stratus is the lowest of all clouds and is less commonly encountered. The base of a stratus cloud can be as low as the surface of the earth, meaning that a heavy fog is actually a cloud on the surface of the earth! Stratus clouds can produce light rain, ie. drizzle.

So now we have described clouds on all altitudes, but one cloud type is still missing. The last cloud type cannot be classified to a single altitude level, it crosses all of them. The last cloud type is the cumulonimbus cloud. From the name we can immediately see that it is a puffy cloud producing precipitation. Cumulonimbus clouds are actually thunderstorm clouds, their great vertical extent giving the possibility to generate electrical potential energy.

Each cloud genus is divided into several species, which are further divided into subspecies. For example, altocumulus stratiformis undulatus is a mid-level cloud (alto) made of multiple individual tufts of cloud (cumulus) which are coalesced and are covering a large portion of the sky (stratiformis) forming into a wave-like pattern (undulatus). Species and subspecies are partly repeated through all cloud genus.