The low-level clouds - Summary



  • In the previous posts we wrote about all low-level clouds, like Cumulus, Stratocumulus, Stratus and Cumulonimbus. All of the low-level clouds have their base under 2 000 m (6500 ft). Let's recapitulate and add some new information about them.

    photo: NOAA;desc: Symbols for all of the low level clouds used in meteorology.;link: https://www.wpc.ncep.noaa.gov/dailywxmap/plottedwx.html;licence: cc

    Cumulus is a nice cloud that usually travels alone. Its top is often in the shape of a cauliflower. The base is darker and flat, but the body can be really white. It is created by convection of saturated air and condensation of the water vapour.

    Cumulus humilis is a flattened Cumulus that cause no precipitation. It usually appears in front of a summer anticyclones.

    Cumulus mediocris has its horizontal size quite similar to the vertical size. In spring, Cumulus mediocris can reach the zero isotherm and water drops or little ice crystals can appear. They can fall down in showers. But in summer is the zero isotherms higher and only very rare precipitation is possible.

    Cumulus congestus has its vertical size much bigger than the horizontal. Therefore it is sometimes called towering cumulus. This species quite often grow in the size of Cumulonimbus and so it can signal a storm ahead!

    Cumulus fractus is only rest of a Cumulus after precipitation.

    Stratus is a grey cloud layer with a uniform base that can cause light rain, drizzle or little ice crystals. You can recognize a Sun through this cloud. It can transform into fog and back as it goes to the mountains. It is created by radiative cooling, a transformation from fog or by turbulence. It usually appears in winter in foothills at the back of an anticyclone together with an inversion.

    Stratus nebulosus is a typical Stratus cloud and Stratus fractus is what remains after it.

    Stratocumulus is grey or whitish bigger or smaller groups or layers of clouds. It looks like it consists of many smaller clouds. It usually causes no precipitation, but light rain or snow can occur. Sun is mostly not visible through this cloud type. It is created by a combination of Stratus and Cumulus generation, so by radiative cooling and convection. Stratocumulus can come before bad weather (before a storm, with a warm front,...)

    Stratocumulus stratiformis is a lightly deformed flat layer, Stratocumulus lenticularis looks like a lens with a smooth surface, Stratocumulus castellanus have towers that increases and grows from its base and Stratocumulus volutus is a big rolling cloud.

    Cumulonimbus is a huge and dense cloud with great vertical magnitude. A part of its top is flat and smooth or fibrous that looks like an anvil. Is it a typical precipitation cloud that hides both water drops and ice crystals in it. The precipitation is very intensive, heavy rain and thunderstorms. It is common in summer, in winter is the tropopause low and therefore the Cumulonimbus is smaller but possible. It is created from Cumulus congestus and often goes before a cold front.

    Cumulonimbus calvus is a lower stage of Cumulonimbus. Its top is like cauliflower and sometimes it can spread horizontally and create a shape of a veil or a canvas.

    Cumulonimbus capillatus is a mature stage that has a full anvil formed. It is a cloud of bad weather (thunderstorms).

    photo: Fadly Halim;desc: Low level cloud Cumulus above a boat.;link: https://www.publicdomainpictures.net/en/view-image.php?image=22321&picture=boat-under-clouds;licence:cc

    If you want to learn more, see the articles about the species of each types.





  • @Gkikas-LGPZ Thank you for your respond. It was edited. My mistake.



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