Abstract View
Process Level Modeling of Vertically Resolved New-particle Formation at the Southern Great Plains Observatory
O'DONNELL SAMUEL, James Smith, Ali Akherati, John Shilling, Fan Mei, Hubbe John, Stephen Springston, Joel A. Thornton, Siegfried Schobesberger, Emma D'Ambro, Ben H. Lee, Charles Long, Chongai Kuang, Jerome Fast, Anna Hodshire, Charles He, Michael J. Lawler, Jeffrey R. Pierce, Shantanu Jathar, Colorado State University
Abstract Number: 28
Working Group: Aerosol Physics
Abstract
New particle formation (NPF) is a significant source of cloud condensation nuclei and aerosol number concentrations in the atmosphere. Many studies investigate NPF at the surface, but fewer studies examine the vertical profile of NPF across the boundary-layer mixed layer (ML) and residual layer (RL). The upper ML and RL can have favorable conditions for NPF, such as low condensation/coagulation sinks, low temperatures, high relative humidity, rapid photochemistry, and elevated concentrations of precursor species.
To investigate the driving processes and vertical profile of NPF, we used a model of the boundary-layer column along with aircraft- and ground-based observations from the two Holistic Interactions of Shallow Clouds, Aerosols, and Land Ecosystems (HI-SCALE) campaign deployments in 2016 at the Atmospheric Radiation Measurement, Southern Great Plains observatory. During HI-SCALE, 8 sustained NPF events were observed at the ground, 2 of which were observed by the aircraft as starting near the top of the boundary-layer prior to being observed by surface instruments. The SOM-TOMAS column model simulates gas-phase oxidation reactions, thermodynamics, gas-particle partitioning, aerosol microphysics, vertical mixing, and nucleation using two state-of-the-art organic and inorganic nucleation schemes.
The model is able to predict the occurrence of nucleation and generally can predict the subsequent aerosol mass and number concentrations. Additionally, for several of the modeled nucleation events during HI-SCALE, vertical mixing of freshly nucleated particles from the upper ML or RL (where precursor concentrations were elevated) to the surface model layer was necessary to explain the observed aerosol size distribution at the surface. Finally, we find that the vertical profiles of temperature and precursor concentrations as well as the dynamic evolution of the ML with time can explain much of the vertical profile of nucleation in the model.