<P> Cirrus clouds are formed when water vapor undergoes deposition at high altitudes where the atmospheric pressure ranges from 600 mbar at 4,000 m ( 13,000 ft ) above sea level to 200 mbar at 12,000 m ( 39,000 ft ) above sea level . These conditions commonly occur at the leading edge of a warm front . Because humidity is low at such high altitudes , this genus - type tends to be very thin . Cirrus clouds are composed of ice crystals that originate from the freezing of super cooled water droplets in regions where air temperature is lower than - 20 ° C or - 30 ° C. Cirrus usually occur in fair weather. They are formed when it is high enough to be cold and freeze the water drops into ice . They sometimes may be caused by turbulence and wind shear , or by upper - tropospheric convection . Sometimes they are like blown out ice - crystals spreading from the top of a dying cumulonimbus . </P>
<P> Cirrus clouds are formed when water vapor undergoes deposition at high altitudes where the atmospheric pressure ranges from 600 mbar at 4,000 m ( 13,000 ft ) above sea level to 200 mbar at 12,000 m ( 39,000 ft ) above sea level . These conditions commonly occur at the leading edge of a warm front . Because humidity is low at such high altitudes , this genus - type tends to be very thin . Cirrus clouds are composed of ice crystals that originate from the freezing of super cooled water droplets in regions where air temperature is lower than - 20 ° C or - 30 ° C. Cirrus usually occur in fair weather. They are formed when it is high enough to be cold and freeze the water drops into ice . They sometimes may be caused by turbulence and wind shear , or by upper - tropospheric convection . Sometimes they are like blown out ice - crystals spreading from the top of a dying cumulonimbus . </P>
high level clouds that are mainly composed of ice crystals
high level clouds that are mainly composed of ice crystals
Cirrus clouds
Cirrus clouds