Virga
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- For the genus of grass skipper butterflies, see Virga (butterfly). See Virga (planetary geology) for virgae, a type of surface feature found on Titan.
In meteorology, virga is precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because the air pressure increases closer to the ground. It is very common in the desert and in temperate climates. It is also common in the Southern United States during summer.
Virga can cause very interesting weather effects, because as rain is changed from liquid to vapor form, it removes heat from the air due to the high heat of vaporization of water. In some instances, these pockets of colder air can descend rapidly, creating a dry microburst which can be extremely hazardous to aviation.
Virga also has a role in seeding storm cells whereby small particles from one cloud are blown into neighboring supersaturated air and act as nucleation particles for the next thunderhead cloud to begin forming.
Virga can produce dramatic and beautiful scenes, especially during a red sunset. The red light can be caught by the streamers of falling precipitation, while aloft, winds push the bottom ends of the virga so it falls at an angle, making the clouds appear to have commas attached.
[edit] Extraterrestrial versions
Sulfuric acid rain in the atmosphere of Venus evaporates before reaching the ground due to the immense heat near the surface.
[edit] See also
[edit] External links
cs:Virga de:Virga (Wolke) es:Virga (Meteorología) fr:Virga it:Virga he:וירגה hu:Virga no:Virga nn:Virga pl:Virga pt:Virga sl:Virga sv:Fallstrimmor zh:幡狀雲
