This is a past event.

This will be a hybrid event, the speaker will be remote while the audience is encouraged to gather in M&M U113.

The Richard E. Honrath Memorial Lecture

Bo Zhang, Senior Research Scientist at the National Institute of Aerospace will give a talk on:

Constraints From Airborne Radionuclides on Convective Transport and Aerosol Scavenging in GEOS and GEOS-Chem Global Models

Parameterizations of atmospheric chemical and physical processes in global models unavoidably introduce biases in simulating the lifecycles of tropospheric trace gases and aerosols. Addressing these biases is crucial for improving climate modeling. Airborne radionuclides serve as excellent tracers to provide unique constraints on convective transport and aerosol scavenging in global models. Rn-222, an inert gas emitted from soil, is particularly useful for assessing biases associated with convective transport, due to its relatively simple pathway in the atmosphere. The vertical distribution of Rn-222 primarily reflects the convective transport process due to the relatively short decay lifetime (a few days). Intercomparison of simulated Rn-222 distributions has been an efficient approach to compare transport characteristics with respect to boundary-layer turbulent mixing and convection. Pb-210, with a radioactive half-life of 22.3 years, is produced by the radioactive decay of Rn-222 in the atmosphere. It attaches to ambient submicron aerosols in the atmosphere, making it an excellent tracer for studying cloud scavenging of aerosols. Pb-210 measurements from ground sites, NASA aircraft campaigns, and balloons have been used to constrain cloud scavenging parameterization of aerosols. 

In “bulk” aerosol models, which lack aerosol microphysics, scavenging parameterizations for stratiform precipitation use fixed scavenging coefficients, leading to substantial uncertainties. We implemented an aerosol size-dependent below-cloud scavenging (washout) parameterization and developed a more physically based in-cloud scavenging (rainout) scheme coupled with two-moment cloud microphysics in GEOS/GOCART model. The new parameterizations calculate aerosol below-cloud scavenging coefficients based on a size-dependent collision efficiency between aerosol particles and raindrops (or snow crystals). In-cloud scavenging efficiency is derived from newly formed cloud droplet and ice crystal number concentrations in the two-moment cloud microphysics. These developments have led to reasonable simulations of global Pb-210 aerosol tracer and some improvements in simulated sea salt concentrations. 

The Richard E. Honrath Memorial Lecture is a Joint EPSSI/Environmental Engineering Graduate Seminar honoring the memory of Richard E. Honrath Jr., who was a faculty member in the Civil, Environmental, and Geospatial Engineering and Geological and Mining Engineering and Sciences Departments. Professor Honrath was a co-founder of Michigan Tech's Atmospheric Sciences Doctoral Degree Program. He died tragically in a kayaking accident in April 2009