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MYSTERY
CLOUDS:
CLOUDS IN THE LOWER ATMOSPHERE
There are many types of clouds in the troposphere. They
are distinguished by their shapes and sizes and height. They can appear
bright white in color to very grey. Although it is possible for cloud ice
crystals to form without nucleation sites in the troposphere, this is not
usually the case. Aerosols, small airborne particles or
non cloud droplets, are common nucleation sites. Aerosols have sizes on
the order of 0.1 to micrometers. They come from a variety of sources including
wind generated dust, volcanic ejections, sea water spray and smoke. Aerosols
occur in concentrations of about 1000 particles per cubic centimeter and
so are widely available for cloud nucleation. Tropospheric clouds typically
occur at temperatures of -10C to -50C.
For more information:
http://www.weatherwizkids.com/cloud.htm
http://www.usatoday.com/weather/wcloud0.htm
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