Title: The Impact of Organic Aerosol Volatility on Aerosol Microphysics for Global Climate 
Modeling Applications

Presenter: Chloe Gao

Abstract: A newly developed box model, MATRIX-VBS [Gao et al., 2017], includes the volatility-
basis set (VBS) framework in an aerosol microphysical scheme MATRIX (Multiconfiguration 
Aerosol TRacker of mIXing state) [Bauer et al., 2008], which is a module within GISS ModelE 
that resolves aerosol mass and number concentrations and aerosol mixing state. By including 
the gas-particle partitioning and chemical aging of semi-volatile organic aerosol in MATRIX, we 
were able to examine its effects on the growth, composition and mixing state of particles. 
MATRIX-VBS is unique and advances the representation of organic aerosols in Earth system 
models by greatly improving the traditional and very simplistic treatment of organic aerosols as 
non-volatile and with a fixed size distribution. Idealized cases representing Beijing, Mexico City, 
a Finnish and a Southeast U.S. forest were simulated, and we investigated the evolution of mass 
concentrations and volatility distributions for organic species across the gas and particle 
phases, as well as their mixing state among aerosol populations. To test and simplify the model, 
a Monte-Carlo analysis is performed to pin point which processes affect organics the most 
under varied chemical and meteorological conditions. Since the modelŐs parameterizations 
have the ability to capture a very wide range of conditions, all possible scenarios on Earth 
across the whole parameter space, including temperature, humidity, location, emissions and 
oxidant levels, are examined. These simulations provide information on which parameters play 
a critical role in the aerosol distribution and evolution in the atmosphere and which do not, and 
that will facilitate the simplification of the box model, an important step in its implementation 
in the global model GISS ModelE as a module.