Contrail-Cirrus - Man-made Experiments on Complex Cloud Physics

Kurzfassung

Contrails represent reproducible prototypes of cirrus clouds which are easier to understand scientifically and offer better chances for experimental investigations than natural cirrus. Cirrus clouds are thin ice clouds covering about 50 % of the Earth. They affect climate by contributions to the Earth albedo and the natural Earth Greenhouse effect, with a net global warming effect. The physical and chemical effects of ice clouds are complex. Contrails are a specific type of cirrus clouds induced in cool and humid air masses by aircraft. Conrail cirrus contribute the largest and most uncertain part to the climate forcing from aviation. Contrail formation is predictable and controllable to some extent. Hence, contrail cirrus formation can be interpreted as a man-made experiment in the atmosphere. Since the first observations of contrails in 1915, the investigation of contrail formation led to important general insight into the atmosphere system, such as the detection of ice supersaturation, homogeneous and heterogeneous ice particle formation, and the Brewer-Dobson circulation. This talk will introduce cirrus and contrails and describe results from a recent field experiment ML-CIRRUS performed with a fully-instrumented research aircraft (HALO). For experiment planning, contrail cirrus has been predicted with a combination of numerical weather prediction (from ECMWF) and a contrail cirrus prediction model (CoCiP) which we developed in recent years. Model and measurement results will be presented and discussed.