Title : Contrail cirrus modeling, ongoing validation, and remarks on vertical air motions
Abstract : Contrails form behind aircraft from water vapor and soot engine emissions in sufficiently cold air and may persist for hours in ice supersaturated air masses. Contrail cirrus impacts the radiative budget of the Earth atmosphere system with positive longwave and negative shortwave radiative forcing (RF) contributions depending on sunshine, weather and aircraft routing. Aviation induced contrail cirrus may impact climate to a degree comparable to that of past aviation CO2 emissions. Aviation climate impact may be reduced by proper route selection leading to minimum energy forcing (time and space integrated RF). Here we describe the Contrail Cirrus Prediction model CoCiP which simulates the lifecycle of contrails and computes the time and space integrated RF for given weather and traffic information. The model results compare favorably with a wide set of in situ and remote sensing observation. The method has been applied to study various mitigation strategies (Teoh et al., 2020). In order to determine the total aviation induced shortwave and longwave RF, we started comparing model and satellite data for the periods with high and low traffic before after COVID 19. The formation of ice supersaturated airmasses requires vertical lifting motions. As an aside, a recent study (Schumann, 2019) on relating mesoscale vertical motions in the upper troposphere and lower stratosphere to horizontal divergent motions will be mentioned.