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Contrails

Contrails of different age seen with the MOMS-2P (on the PRIRODA Module of the MIR station) May 8th 1998 at 8:53 UTC over the Channel region

The impact of air-traffic on climate is not only restricted to the emission of combustion products like soot, HO2, CO2 and NOX. If the ambient air is cold and moist enough the aircraft engines also trigger the formation of clouds. As long as they are young, they are easily identified as contrails. Neither the amount of the additional cloud coverage nor the resulting effect on net radiation is known sufficiently. In contrast to lower level clouds these thin and high clouds are warming the earth-atmosphere system.

An algorithm to derive the amount of linear contrails from satellite data was developed at Institut für Physik der Atmosphäre at Oberpfaffenhofen. This method is used here to derive contrail statistics over Europe and Southeast- and East Asia. They are used at NASA for the continental USA.

Investigations on the details of contrail development have been performed by in-situ measurements and numerical models of the microscopic cloud physics. To estimate the global effect of contrails we use a climate model.

Aging contrails often cannot be discriminated from natural cirrus clouds and the combustion products of the air traffic might lead to changes in the cirrus formation process. Research is going on to determine the amount and effect of this additional cloudiness.