Alexander Naiman

The effects of aircraft on climate and pollution. Part I: Numerical methods for treating the subgrid evolution of discrete size- and composition-resolved contrails from all commercial flights worldwide

This paper provides and evaluates mass conservative, positive-definite, unconditionally-stable, and non-iterative numerical techniques for simulating the evolution of discrete, size- and composition-resolved aerosol and contrail particles in individual aircraft exhaust plumes in a global or regional 3-D atmospheric model and coupling the subgrid exhaust plume information to the grid scale. Such treatment represents a new method of simulating the effects of aircraft on climate, contrails, and atmospheric composition. Microphysical processes solved within each plume include size-resolved coagulation among and between aerosol and contrail particles and their inclusions, aerosol-to-hydrometeor particle ice and liquid nucleation, deposition/sublimation, and condensation/evaporation. Each plume has its own emission and supersaturation, and the spreading and shearing of each plumes cross-section are calculated as a function of time. Aerosol- and contrail-particle core compositions are tracked for each size and affect optical properties in each plume. When line contrails sublimate/evaporate, their size- and composition-resolved aerosol cores and water vapor are added to the grid scale where they affect large-scale clouds. Algorithm properties are analyzed, and the end-result model is evaluated against in situ and satellite data.

Large Eddy Simulations of Persistent Aircraft Contrails

A three-dimensional large eddy simulation (LES) model has been used to study the development of persistent aircraft condensation trails (contrails) under a variety of atmospheric and initial conditions. The LES solves the incompressible Navier-Stokes equations with a Boussinesq approximation for buoyancy forces. Contrail ice particles are modeled using a Lagrangian tracking approach, with water mass and heat exchange coupled between the vapor and solid phases. Three sets of simulations vary the atmospheric turbulence environment, initial aircraft wake flow field, and ambient humidity to investigate the sensitivity of contrail properties to these parameters. Higher levels of turbulence and vertical shear, larger aircraft, and higher ambient humidity are all found to increase the ice mass present in the contrail to some extent. Each of these parameters also affects the optical properties and area coverage of the resulting contrail. These simulations provide sensitivity data that are used to improve a model of aircraft exhaust plume dynamics implemented in a global scale climate model.

A Low-Order Contrail Model for use with Global-Scale Climate Models

are incorporated in the model. We also show some examples of the application of this model and compare them to other computational contrail studies.