Abstract
Abstract. A new model to simulate and predict the properties of a large ensemble of contrails as a function of given air traffic and meteorology is described. The model is designed for approximate prediction of contrail cirrus cover and analysis of contrail climate impact, e.g. within aviation system optimization processes. The model simulates the full contrail life-cycle. Contrail segments form between waypoints of individual aircraft tracks in sufficiently cold and humid air masses. The initial contrail properties depend on the aircraft. The advection and evolution of the contrails is followed with a Lagrangian Gaussian plume model. Mixing and bulk cloud processes are treated quasi analytically or with an effective numerical scheme. Contrails disappear when the bulk ice content is sublimating or precipitating. The model has been implemented in a "Contrail Cirrus Prediction Tool" (CoCiP). This paper describes the model assumptions, the equations for individual contrails, and the analysis-method for contrail-cirrus cover derived from the optical depth of the ensemble of contrails and background cirrus. The model has been applied for a case study and compared to the results of other models and in-situ contrail measurements. The simple model reproduces a considerable part of observed contrail properties. Mid-aged contrails provide the largest contributions to the product of optical depth and contrail width, important for climate impact.
Highlights
Contrails are thin linear ice particle clouds which form in the atmosphere behind cruising aircraft because of mixing of the emitted water vapor with cold ambient air leading to local liquid saturation, condensation of water on aerosols, and subsequent freezing (Schmidt, 1941; Appleman, 1953; Schumann, 1996)
The formation of ice particles in the exhaust jet at time scales of 0.1 s to 20 s (Karcher et al, 1998; Paoli and Garnier, 2005; Paoli et al, 2008), their spreading and downwash (Scorer and Davenport, 1970) with the wake vortices forming behind aircraft at time scales of 1 min to 20 min (Lewellen and Lewellen, 2001) and their transition into widespread cirrus clouds and final decay at timescales of less than a hour to possibly days (Unterstrasser and Gierens, 2010a), are difficult to compute in one model
The initial number of ice particles is a result of liquid droplets which form by nucleation on emitted and ambient aerosols and which freeze shortly thereafter (Karcher et al, 1996; Fahey et al, 1999)
Summary
Contrails are thin linear ice particle clouds which form in the atmosphere behind cruising aircraft because of mixing of the emitted water vapor with cold ambient air leading to local liquid saturation, condensation of water on aerosols, and subsequent freezing (Schmidt, 1941; Appleman, 1953; Schumann, 1996). The formation of ice particles in the exhaust jet at time scales of 0.1 s to 20 s (Karcher et al, 1998; Paoli and Garnier, 2005; Paoli et al, 2008), their spreading and downwash (Scorer and Davenport, 1970) with the wake vortices forming behind aircraft at time scales of 1 min to 20 min (Lewellen and Lewellen, 2001) and their transition into widespread cirrus clouds and final decay at timescales of less than a hour to possibly days (Unterstrasser and Gierens, 2010a), are difficult to compute in one model. Simpler models with parameterized physics are required, providing proper results for the whole contrail life-cycle and for the global aircraft fleet under realistic meteorological conditions, with far less computing time. Such a model, the “Contrail Cirrus Prediction Tool” (CoCiP), is described in this paper. This paper describes the details of the basic model concept, presents global results for illustration, and compares results for a few special cases with other models and observations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
