A review of satellite remote sensing of aircraft-induced contrails and investigation of their potential role in regional climate change

Condensation-trails, or 'contrails', have a net warming effect on the climate system. They form in the wake of jet aircraft, as exhaust-gases mix with cold and humid ambient air. The climate impact of contrails is largest at night and in winter; even though air-traffic densities are lowest at these times. Depending on ambient atmospheric conditions, contrails can; persist for several hours; grow to several kilometers in length, and trigger additional cirrus cloud formation as they spread. Cirrus cloud cover is increasing in flight corridors as they become increasingly congested. A small, but statistically significant, increase in cirrus coverage has been observed for the North Atlantic flight corridor; in contrast to small negative trends in cirrus elsewhere. Presently, a complete set of validation data for model studies of contrail-cirrus is missing. However, by building upon existing automated-contrail-detection techniques, a satellite-derived cloud and contrail climatology for Ireland will be compiled based on two decades of archived high-resolution satellite imagery. Combining meteorological measurements concurrent with satellite overpasses, the optimal meteorological conditions for contrail formation and persistence will be investigated. The radiative effect of contrails on the atmospheric column radiation budget, and their contribution to regional atmospheric warming, can then be assessed. This paper provides a review of different methods by which contrails and cirrus clouds have been observed from satellite imagery and a discussion of their potential role in climate change.