6.3: Cloud Naming Conventions
- Page ID
- 46233
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Once a cloud forms, how do we know what to call it? Clouds form in many environments and look different depending on those environments, and depending on whether they’re composed of liquid droplets or ice crystals. The following diagram gives a brief overview of the many cloud types, along with their common abbreviations.
Clouds can be identified based on their appearance, shape, and altitude. The two primary cloud categories are cumuliform and stratiform clouds.
By Appearance and Shape
Cumuliform clouds develop as a result of vertical motions by atmospheric instability. They are convective clouds meaning that they form in air parcels that are buoyant and are undergoing convection, which is the transfer of heat or mixing within a fluid due to warm air rising and cool air sinking. Examples of cumuliform clouds include cumulus, cumulus congestus, and cumulonimbus.
Stratiform clouds are horizontally layered clouds. They tend to spread into wide regions, and take on an appearance of a sheet or blanket. They typically form when a layer of air is brought to saturation but is thermodynamically stable, or when a convective cloud meets a stable layer and spreads out in a layered fashion. Examples of stratiform clouds include nimbostratus, stratus, altostratus, cirrostratus, and cirrus.
By Water Phase
Clouds composed of only liquid water droplets are called “warm clouds”, and typically have clearly defined edges. Low altitude clouds are usually warm clouds.
Clouds made up of only ice crystals are called “cold clouds” and typically have fuzzy looking edges. The edges look fuzzy and not well defined because it takes longer to go from the ice phase to the vapor phase as compared to warm clouds. This transition time scale results in a larger cloud to dry air transition region. High altitude clouds are always cold clouds.
Clouds composed of liquid water and ice crystals are called “mixed phase clouds”. It is difficult to distinguish by eye whether a cloud is mixed phase. Often the decision comes down to the height of the cloud, knowing that clouds that extend from the surface up high in the atmosphere likely have a mixture of both liquid droplets and ice crystals.
By Altitude
Clouds at a high altitude have the prefix “cirro” or “cirrus”. Due to the high altitude, the cirrus and cirrostratus are made out of ice crystals.
Clouds at mid-altitude have the prefix “alto”. They are usually made out of liquid droplets, but can be a mixture between liquid droplets and ice crystals.
Low level clouds don’t have a particular prefix.
By Characteristics
The prefix “nimbo” or suffix “nimbus” indicates a precipitating cloud. Nimbostratus usually have light to moderate precipitation, whereas cumulonimbus or thunderstorm clouds have heavy precipitation and sometimes even hail.
Other
The above clouds represent the primary cloud types, but many other cloud names and cloud types are used in atmospheric sciences. A few of the more common cloud names are given below.
Lenticular clouds are stationary lens-shaped clouds with a smooth appearance that usually forms over the summit of a mountain or on the lee wave crest. They are also referred to as lee-wave clouds or mountain-wave clouds.
Mammatus clouds are formed from downward convection, typically in the anvil portion of a cumulonimbus. They have a distinctive look that makes them easy to spot, especially at sunset. They are made up of hanging pouches that look a little bit like udders.
Fog
A cloud that forms at or near the ground is called fog. The main types of fog are upslope, radiation, advection, precipitation or frontal, and steam fog.
Upslope, radiation, and advection fogs develop due to cooling. Upslope fog develops as stable, moist air rises over topography like a hill or mountain. Radiation fog occurs over land as radiational cooling lowers the air temperature to its dew point temperature. Radiation fog usually occurs during calm, clear nights. Advection fog forms as warm, moist air flows over a colder surface and the air cools to its dew point temperature.
Frontal and steam fogs are formed by the addition of water vapor. Frontal fog develops when warm raindrops evaporate in a colder airmass. Steam fog or sea smoke forms as cold air moves over warmer water.