Exploring the Radiative Effect and Climate Impact of Contaminated Contrails

Abstract:

As an impact of human aviation activities, contrails have drawn a great deal of attention. There have been numerous investigations into the contrail properties, radiative effects, and climate impact. However, very little effort has been focused on the impact of contaminated contrails. Generated by the combustion process within the aircraft engine, the aerosols and exhaust gases frequently influence contrail formation. Contrail ice crystals contaminated by soot particles have been found to exhibit dramatically different light scattering properties from those of pristine crystals. In this study, we employ state-of-the-art light scattering computational capabilities to calculate the single-scattering properties of soot-contaminated contrails. The contaminated contrail particle is assumed to be a hexagonal ice column containing several soot particles. The invariant imbedding T-matrix method and the Ray-by-Ray geometry optics method are combined to construct a simplified yet novel set of contaminated contrail optical properties. The bulk optical properties are calculated based on the data set and are parameterized for use in the Community Atmospheric Model. Using global contrail retrievals from satellite remote sensing observations in 2006 and 2012, simulations are conducted using the general circulation model to analyze contaminated contrail radiative effects as well as their climatic sensitivities. Our results show that the contaminated contrail is significantly more absorbing than pristine contrail in the shortwave spectrum. As a result, much stronger contrail radiative impact and climate feedback are found. Several sensitivity studies are also implemented to quantify the effect of contrail contamination.