07/25/2014 - 2:30pm
Joyce E. Penner (University of Michigan, Ann Arbor)
Title: "The CAM/IMPACT/CoCiP Coupled Climate Model: Radiative forcing by aircraft in spreading contrails and large-scale cirrus"
Radiative forcing by aircraft soot in large-scale cirrus clouds has been estimated to be both positive and negative. Here, we study different model choices for the treatment of aerosols that have led to this positive and negative forcing. We also summarize results from the coupled CAM/IMPACT/CoCiP model, which is able to treat both the formation of contrails, spreading contrails (contrail cirrus), and the effects of aircraft soot on large-scale cirrus clouds. We use this model to examine the total forcing of aircraft soot within the climate system and we evaluate the effects of the coupling of the hydrological cycle within CAM with the CoCiP contrail model. The large-scale cloud effects assume that the fraction of soot particles that have been processed through contrails are good heterogeneous ice nuclei (IN).