Contrail Cirrus and Cirrus Cloud Thinning: Intertwined Climate Strategies

Among the three widely known solar radiation management/modification (SRM) methods of stratospheric aerosol injection (SAI), marine cloud brightening (MCB), and cirrus cloud thinning (CCT), CCT is the least studied and most uncertain. CCT could have significant advantages relative to either SAI or MCB in terms of avoiding potential adverse effects on the hydrological cycle due to its action on outgoing longwave rather than incoming shortwave radiation. The study on CCT efficacy is very limited and has large uncertainties. Cirrus clouds not only form naturally but can also be induced anthropogenically as aviation contrails spread into cirrus clouds, which is a major contributor to aviation climate warming and with large uncertainties as well. CCT and the ongoing efforts in mitigating climate impacts of contrail cirrus are intertwined. Both face uncertainties primarily driven by microphysical processes and their representation in global models. By leveraging extensive field measurements related to contrail cirrus, we can address key knowledge gaps in both contrail cirrus mitigation and CCT efficacy. Our approach integrates measurement-informed/guided plume-scale, large-eddy, and global simulations to refine climate/radiative impact assessments, enhance contrail mitigation strategies, and obtain critical insights to better understand and improve CCT efficacy.

Fangqun Yu obtained his Ph.D. in 1998 from the University of California, Los Angeles in atmospheric science. Currently, he is a tenured faculty member of the Atmospheric Sciences Research Center at the University at Albany, State University of New York. His research has focused on the formation of particles and contrails in aircraft plumes, theories of new particle formation in the atmosphere, size-resolved particle microphysics, and climatic and environmental impacts of atmospheric particles. He develops and applies a size-resolved advanced particle microphysics (APM) model across plume, local, and global scales. The APM model has been coupled with widely used community models, including GESO-Chem, WRF-Chem, WRF-CMAQ, CESM2, and E3SM. His recent research employing APM at both plume and global scales has shed new insights into SRM via SAI. His group is also working on connecting the contrail cirrus study to CCT and shipping emissions to MCB, the other two proposed approaches of SRM. With over 180 peer-reviewed publications and a Google Scholar h-index of 57, his work spans fundamental particle microphysics, aerosol-cloud-climate interactions, contrail formation and climate implications, climate intervention, health effects of ultrafine particles, and machine learning applications in global aerosol modeling.

Bernd Kärcher has many years of experience in developing atmospheric process models, understanding the microphysical and chemical behavior and atmospheric impacts of airborne aerosol particles and ice-phase clouds, and integrating experimental data with cloud physical theory in order to develop parameterization schemes for large-scale models. His contributions to atmospheric ice formation processes and the physics of ice clouds have led to significant changes in cloud schemes within numerical weather prediction and climate models. He was involved in, and received outside funding from, numerous projects in EU framework programs, German Federal Ministry of Science and Education and Research (BMBF) collaborative programs, and the German Helmholtz Society (HGF). He acted as a responsible scientist and administrator of DLR-IPAs Aviation-Climate projects (1999-2009), securing significant internal funding that included several aircraft field campaigns on contrail- and cirrus-related problems.

Richard Moore is an airborne research scientist at NASA’s Langley Research Center. His research examines the role of atmospheric particles in influencing cloud formation, air quality, and climate. He has participated in more than 20 airborne field campaign deployments in both instrument and project scientist roles. He designs and executes airborne field campaigns to measure aircraft engine emissions and contrails at cruise altitudes. A particular research interest is to understand how sustainable aviation fuels, low-particle-emitting engine technologies, and hydrogen-burning engines might impact the formation of climate-altering contrail cirrus clouds. Moore received his Ph.D. in chemical and biomolecular engineering from Georgia Tech and B.S. and M.S. degrees in chemical engineering from Bucknell University. He is a member of the American Association for Aerosol Research, American Geophysical Union, and American Institute of Aeronautics and Astronautics.

Martin Rieth is a computational scientist specializing in computational fluid dynamics, with a focus on reacting and multiphase flows. He is presently a senior member of technical staff, Sandia National Laboratories. His research aims to uncover fundamental physical insights through large-scale direct numerical simulations and large eddy simulations of complex flow systems. His current interests include simulating atmospheric aerosol processes targeting solar radiation management strategies.