Post by Icarus on Mar 24, 2008 11:15:14 GMT -5
Cloud Reading:
CIRRUS CLOUDS
These clouds may be leftover from thunderstorms, but usually indicate that an upper air disturbance is approaching, and the weather will change within 24 hours.
Cirrus clouds are characterized by thin, wisplike strands, often accompanied by tufts, leading to their common (non-standard) name of 'mare's tails'. Sometimes these brownish clouds are so extensive that they are virtually indistinguishable from one another, forming a veil or sheet called "cirrostratus". Sometimes convection at high altitudes produces another form of cirrus called "cirrocumulus", a pattern of small cloud tufts which include droplets of supercooled water.
Many cirrus clouds produce hairlike filaments made of the heavier ice crystals that precipitate from them. These "fall streaks", a form of virga, often indicate the difference in the motion of air (wind shear) between the upper part of the cirrus cloud and the air below it. Sometimes the top of the cirrus cloud is moving rapidly above a slower layer of air, or the streak is falling into a faster moving lower layer. The directions of these winds can also vary.
Cirrus usually form at altitudes above 8000 meters (26,000 feet). The fall streaks may appear straight when wind shear is absent, giving the clouds the appearance of a comma (cirrus uncinus), or tangled, an indication of high-level turbulence. The falling ice crystals evaporate before reaching the ground.
Cirrus clouds trap and reflect infrared radiation (heat) beneath them (greenhouse effect), but also reflect sunlight to some extent (albedo). It has not yet been determined for certain whether the net effect of cirrus clouds is to warm or cool the earth. Much of the difficulty lies in modelling the albedo effect of clouds composed of various size and shape crystals. Older models tended to underestimate the albedo effect of cirrus. Refinements of these models will improve climate predictions.
If there are many cirrus clouds in the sky it may be a sign that a frontal system or upper air disturbance is approaching; usually meaning the weather will change within the next 24 hours. Cirrus clouds can also be the remnants of a thunderstorm. A large shield of cirrus and cirrostratus typically accompanies the high altitude outflow of hurricanes/typhoons. Cirrus clouds have also been observed to develop after the persistent formation of contrails from aircraft.
en.wikipedia.org/wiki/Cirrus_clouds
CIRRUS CLOUDS
These clouds may be leftover from thunderstorms, but usually indicate that an upper air disturbance is approaching, and the weather will change within 24 hours.
Cirrus clouds are characterized by thin, wisplike strands, often accompanied by tufts, leading to their common (non-standard) name of 'mare's tails'. Sometimes these brownish clouds are so extensive that they are virtually indistinguishable from one another, forming a veil or sheet called "cirrostratus". Sometimes convection at high altitudes produces another form of cirrus called "cirrocumulus", a pattern of small cloud tufts which include droplets of supercooled water.
Many cirrus clouds produce hairlike filaments made of the heavier ice crystals that precipitate from them. These "fall streaks", a form of virga, often indicate the difference in the motion of air (wind shear) between the upper part of the cirrus cloud and the air below it. Sometimes the top of the cirrus cloud is moving rapidly above a slower layer of air, or the streak is falling into a faster moving lower layer. The directions of these winds can also vary.
Cirrus usually form at altitudes above 8000 meters (26,000 feet). The fall streaks may appear straight when wind shear is absent, giving the clouds the appearance of a comma (cirrus uncinus), or tangled, an indication of high-level turbulence. The falling ice crystals evaporate before reaching the ground.
Cirrus clouds trap and reflect infrared radiation (heat) beneath them (greenhouse effect), but also reflect sunlight to some extent (albedo). It has not yet been determined for certain whether the net effect of cirrus clouds is to warm or cool the earth. Much of the difficulty lies in modelling the albedo effect of clouds composed of various size and shape crystals. Older models tended to underestimate the albedo effect of cirrus. Refinements of these models will improve climate predictions.
If there are many cirrus clouds in the sky it may be a sign that a frontal system or upper air disturbance is approaching; usually meaning the weather will change within the next 24 hours. Cirrus clouds can also be the remnants of a thunderstorm. A large shield of cirrus and cirrostratus typically accompanies the high altitude outflow of hurricanes/typhoons. Cirrus clouds have also been observed to develop after the persistent formation of contrails from aircraft.
en.wikipedia.org/wiki/Cirrus_clouds