Show simple item record

contributor authorFraser, Alistair B.
contributor authorBohren, Craig F.
date accessioned2017-06-09T16:08:49Z
date available2017-06-09T16:08:49Z
date copyright1992/08/01
date issued1992
identifier issn0027-0644
identifier otherams-61986.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4202827
description abstractThe visual phenomenon called virga, a sudden change in the brightness of a precipitation shaft below a cloud, is commonly attributed to evaporation of raindrops. It is said to be rain that does not reach the ground. The optical thickness of an evaporating rain shaft, however, decreases gradually from cloud base to ground. Thus, it is more likely that virga results from snowflakes melting in descent. Horizontal optical-thickness decreases of more than ten can occur in the short distance over which a snowflake is transformed into a raindrop. This decrease is caused by two factors: a smaller number density of hydrometeors because of the greater fall velocity of raindrops than of equivolume snowflakes, and a smaller scattering cross section: the first of these is dominant. An alternative explanation of virga is that it is precipitation that has not yet reached (rather than does not reach) the ground. This is a plausible explanation given the long time periods it may take hydrometeors, especially snowflakes, to descend from cloud to ground.
publisherAmerican Meteorological Society
titleIs Virga Rain That Evaporates before Reaching the Ground?
typeJournal Paper
journal volume120
journal issue8
journal titleMonthly Weather Review
identifier doi10.1175/1520-0493(1992)120<1565:IVRTEB>2.0.CO;2
journal fristpage1565
journal lastpage1571
treeMonthly Weather Review:;1992:;volume( 120 ):;issue: 008
contenttypeFulltext


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record