Mammatus cloud

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Mammatus cloud seen at Puthenpeedika, India Mammatus cloud at Thrissur puthenpeedika.jpg
Mammatus cloud seen at Puthenpeedika, India
Mammatus clouds formation in Coimbatore, India Mammatus-cloud.jpg
Mammatus clouds formation in Coimbatore, India
Mammatus clouds over the Nepal Himalayas Mammatus clouds in the Nepal Himalayas.jpg
Mammatus clouds over the Nepal Himalayas

Mammatus (also called mamma [1] or mammatocumulus, meaning "mammary cloud") is a cellular pattern of pouches hanging underneath the base of a cloud, typically a cumulonimbus raincloud, although they may be attached to other classes of parent clouds. The name mammatus is derived from the Latin mamma (meaning "udder" or "breast").

Contents

According to the WMO International Cloud Atlas, mamma is a cloud supplementary feature rather than a genus, species or variety of cloud. The distinct "lumpy" undersides are formed by cold air sinking down to form the pockets contrary to the puffs of clouds rising through the convection of warm air. These formations were first described in 1894 by William Clement Ley. [1] [2] [3]

Characteristics

Mammatus clouds on a cumulonimbus capillatus Riesiger Cb mit mammatus.jpg
Mammatus clouds on a cumulonimbus capillatus

Mammatus are most often associated with anvil clouds and also severe thunderstorms. They often extend from the base of a cumulonimbus cloud, but may also be found under altostratus, and cirrus clouds, as well as volcanic ash clouds. [4] When occurring in cumulonimbus, mammatus are often indicative of a particularly strong storm. Due to the intensely sheared environment in which mammatus form, aviators are strongly cautioned to avoid cumulonimbus with mammatus as they indicate convectively induced turbulence. [5] Contrails may also produce lobes but these are incorrectly termed as mammatus. [1]

Mammatus may appear as smooth, ragged or lumpy lobes and may be opaque or translucent. Because mammatus occur as a grouping of lobes, the way they clump together can vary from an isolated cluster to a field of mammae that spread over hundreds of kilometers to being organized along a line, and may be composed of either unequal or similarly-sized lobes. The individual mammatus lobe average diameters of 1–3 kilometres (0.6–1.9 mi) and lengths on average of 12 kilometre (0.3 mi). A lobe can last an average of 10 minutes, but a whole cluster of mamma can range from 15 minutes to a few hours. They are usually composed of ice, but also can be a mixture of ice and liquid water or be composed of almost entirely liquid water.

True to their ominous appearance, mammatus clouds are often harbingers of a coming storm or other extreme weather system. Typically composed primarily of ice, they can extend for hundreds of miles in each direction and individual formations can remain visibly static for ten to fifteen minutes at a time. They usually appear around, before, or even after severe weather.

Hypothesized formation mechanisms

Panorama of mammatus cloud formations in Swifts Creek, Victoria Mammatus cloud panorama.jpg
Panorama of mammatus cloud formations in Swifts Creek, Victoria
Mammatus cloud formation lit by sunset in Visakhapatnam, India Clouds over Vizag 03.jpg
Mammatus cloud formation lit by sunset in Visakhapatnam, India
Several pouches of mammatus clouds seen under cumulonimbus incus in Binan, Laguna, Philippines MammatusCloudsUnderCumulonimbusIncus.jpg
Several pouches of mammatus clouds seen under cumulonimbus incus in Biñan, Laguna, Philippines

The existence of many different types of mammatus clouds, each with distinct properties and occurring in distinct environments, has given rise to multiple hypotheses on their formation, which are also relevant to other cloud forms. [4] [6]

One environmental trend is shared by all of the formation mechanisms hypothesized for mammatus clouds: sharp gradients in temperature, moisture and momentum (wind shear) across the anvil cloud/sub-cloud air boundary, which strongly influence interactions therein. The following are the proposed mechanisms, each described with its shortcomings:

This plenitude of proposed formation mechanisms shows, if nothing else, that the mammatus cloud is generally poorly understood. [1] [8]

References

  1. 1 2 3 4 Schultz, David M.; Hancock, Y. (2016). "Contrail lobes or mamma? The importance of correct terminology" (PDF). Weather. 71 (8): 203. Bibcode:2016Wthr...71..203S. doi: 10.1002/wea.2765 .
  2. Anonymous (1975). International Cloud Atlas. Volume I. Manual on the observation of clouds and other Meteors (PDF). World Meteorological Organization. Archived from the original (PDF) on 2017-07-08. Retrieved 2017-05-13.
  3. Ley, William Clement (1894). Cloudland: A study on the structure and characters of clouds. London, England: Edward Stanford. pp. 104–105.
  4. 1 2 Schultz, David M.; Kanak, Katharine M.; Straka, Jerry M.; Trapp, Robert J.; Gordon, Brent A.; Zrnić, Dusan S.; Bryan, George H.; Durant, Adam J.; Garrett, Timothy J.; Klein, Petra M.; Lilly, Douglas K. (2006). "The Mysteries of Mammatus Clouds: Observations and Formation Mechanisms". Journal of the Atmospheric Sciences. 63 (10): 2409. Bibcode:2006JAtS...63.2409S. doi: 10.1175/JAS3758.1 . S2CID   53128552.
  5. Lane, Todd P.; Sharman, Robert D.; Trier, Stanley B.; Fovell, Robert G.; Williams, John K. (2012). "Recent Advances in the Understanding of Near-Cloud Turbulence". Bulletin of the American Meteorological Society. 93 (4): 499. Bibcode:2012BAMS...93..499L. doi: 10.1175/BAMS-D-11-00062.1 .
  6. Garrett, Timothy J.; Schmidt, Clinton T.; Kihlgren, Stina; Cornet, Céline (2010). "Mammatus Clouds as a Response to Cloud-Base Radiative Heating". Journal of the Atmospheric Sciences. 67 (12): 3891. Bibcode:2010JAtS...67.3891G. doi: 10.1175/2010JAS3513.1 . S2CID   54938314.
  7. Winstead, Nathaniel S.; Verlinde, J.; Arthur, S. Tracy; Jaskiewicz, Francine; Jensen, Michael; Miles, Natasha; Nicosia, David (2001). "High-Resolution Airborne Radar Observations of Mammatus". Monthly Weather Review. 129 (1): 159–166. Bibcode:2001MWRv..129..159W. doi: 10.1175/1520-0493(2001)129<0159:HRAROO>2.0.CO;2 .
  8. Kanak, Katharine M.; Straka, Jerry M.; Schultz, David M. (2008). "Numerical Simulation of Mammatus". Journal of the Atmospheric Sciences. 65 (5): 1606. Bibcode:2008JAtS...65.1606K. CiteSeerX   10.1.1.720.2477 . doi:10.1175/2007JAS2469.1.