Saturday, December 23, 2006

NASA Contrail Study

The Blanket Effect: NASA Contrail Study

Cirrus Cloud and Climate Modifications due to Subsonic Aircraft Exhaust

NASA has recently initiated a program to evaluate the potential effects
of current and future commercial aircraft fleets on atmospheric
chemical processes and climate.

As part of this program, we are modeling the effects of subsonic aircraft exhaust on upper tropospheric cirrus clouds.

sophisticated computer programs, we have developed a detailed ice cloud
microphysical model here at NASA Ames Research Center. The model
simulates cloud processes such as ice crystal formation, growth, and

formation and evolution of aircraft-generated contrails is simulated to
determine what processes and environmental conditions control the
growth, spreading, and dissipation of contrails.

addition, the formation of natural cirrus is simulated with and without
aircraft exhaust soot particles to predict the impact of commercial air
traffic on the frequency of cirrus occurrence and their impact on

Recent observations of cirrus clouds have shown that clear air in the
upper troposphere is often supersaturated with ice. Cirrus do not
always form in these regions due to the lack of natural nuclei to
provide a foundation on which ice crystals form.

If aircraft exhaust soot particles are efficient ice nuclei (as shown in Fig. 1) , then the frequency of cirrus may be significantly enhanced in regions with heavy air traffic

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