Difference between revisions of "Virga"

From Glossary of Meteorology
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<div class="definition"><div class="short_definition">(''Also called'' Fallstreifen, fallstreaks, precipitation trails.) Wisps or streaks of water or [[ice]]  particles falling out of a [[cloud]] but vaporizing before reaching the earth's surface as [[precipitation]].</div><br/><div class="paragraph">Virga is frequently seen trailing from [[altocumulus]] and [[altostratus]] clouds, but also is discernible  below the bases of high-level [[cumuliform]] clouds from which precipitation is falling into a dry  [[subcloud layer]]. It typically exhibits a hooked form in which the streaks descend nearly vertically  just under the precipitation source but appear to be almost horizontal at their lower extremities.  Such curvature of virga can be produced simply by effects of strong vertical [[wind shear]], but  ordinarily it results from the fact that [[droplet]] or [[crystal]] vaporization decreases the [[particle]] terminal  [[fall velocity]] near the ends of the streaks. Under some conditions, virga is associated with dry  [[microbursts]], which are formed as a product of the [[vaporization]]. <br/>''See'' [[cloud classification]].</div></div>
 
<div class="definition"><div class="short_definition">(''Also called'' Fallstreifen, fallstreaks, precipitation trails.) Wisps or streaks of water or [[ice]]  particles falling out of a [[cloud]] but vaporizing before reaching the earth's surface as [[precipitation]].</div><br/><div class="paragraph">Virga is frequently seen trailing from [[altocumulus]] and [[altostratus]] clouds, but also is discernible  below the bases of high-level [[cumuliform]] clouds from which precipitation is falling into a dry  [[subcloud layer]]. It typically exhibits a hooked form in which the streaks descend nearly vertically  just under the precipitation source but appear to be almost horizontal at their lower extremities.  Such curvature of virga can be produced simply by effects of strong vertical [[wind shear]], but  ordinarily it results from the fact that [[droplet]] or [[crystal]] vaporization decreases the [[particle]] terminal  [[fall velocity]] near the ends of the streaks. Under some conditions, virga is associated with dry  [[microbursts]], which are formed as a product of the [[vaporization]]. <br/>''See'' [[cloud classification]].</div></div>
  
''Term edited 14 April 2015.''
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<p>''Term edited 14 April 2015.''</p>
  
 
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Latest revision as of 12:16, 14 October 2016



virga

(Also called Fallstreifen, fallstreaks, precipitation trails.) Wisps or streaks of water or ice particles falling out of a cloud but vaporizing before reaching the earth's surface as precipitation.

Virga is frequently seen trailing from altocumulus and altostratus clouds, but also is discernible below the bases of high-level cumuliform clouds from which precipitation is falling into a dry subcloud layer. It typically exhibits a hooked form in which the streaks descend nearly vertically just under the precipitation source but appear to be almost horizontal at their lower extremities. Such curvature of virga can be produced simply by effects of strong vertical wind shear, but ordinarily it results from the fact that droplet or crystal vaporization decreases the particle terminal fall velocity near the ends of the streaks. Under some conditions, virga is associated with dry microbursts, which are formed as a product of the vaporization.
See cloud classification.

Term edited 14 April 2015.