Seminar: Monday, 14 April, 3:10 pm, CR214
Abstract: 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. Then we introduce 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). We also explore the effect of sulfate deposition on soot in decreasing the ability of contrail-processed soot to act as IN. The calculated total all-sky radiative climate forcing with and without coupling of CoCiP to the hydrological cycle within CAM and its range is reported. We discuss what is needed to narrow the range.
Biography: Joyce E. Penner is the Ralph J. Cicerone Distinguished University Professor of Atmospheric Science at the University of Michigan. Dr. Penner’s research focuses on improving climate models through the addition of interactive chemistry and the description of aerosols and their direct and indirect effects on the radiation balance in climate models. Dr. Penner has been a member of numerous advisory committees related to atmospheric chemistry, global change, and Earth science, and is currently Vice-Chair of the NRC Committee on Earth Science and Applications from Space, charged with overseeing NASA’s Earth Science Program. She was the lead editor and a report coordinator for the Intergovernmental Panel on Climate Change (IPCC) report on Aviation and the Global Atmosphere (1999), was coordinating lead author for 2001 IPCC report Chapter on “Aerosols, their direct and indirect effects”, was a lead author for the Chapter on Understanding and Attributing Climate Change for IPCC (2007), and a review editor for the 2013 IPCC report. She also serves as the Vice President, International Association of Meteorology and Atmospheric Science. She is a Fellow of American Geophysical Union and a Fellow of American Association for the Advancement of Science.