Look Up: Probing the Vertical Profile of New Particle Formation and Growth in the Planetary Boundary Layer With Models and Observations

• Published in: Journal of geophysical research. Atmospheres 2023-02, Vol.128 (3), p.n/a
• Main Authors: O’Donnell, Samuel E., Akherati, Ali, He, Yicong, Hodshire, Anna L., Shilling, John E., Kuang, Chongai, Fast, Jerome D., Mei, Fan, Schobesberger, Siegfried, Thornton, Joel A., Smith, James N., Jathar, Shantanu H., Pierce, Jeffrey R.
• Format: Article
• Language: English
• Subjects: Aerosol chemistry; Aerosol concentrations; Aerosol particles; Aerosols; Atmosphere; Atmospheric models; Boundary layers; Climate; Cloud condensation nuclei; Condensation nuclei; Diameters; Earth surface; ENVIRONMENTAL SCIENCES; Gases; Geophysics; Ground-based observation; Growth rate; Lower troposphere; Measuring instruments; Microphysics; Mixed layer; Modelling; new particle formation; NPF; nucleation; Particle formation; Planetary boundary layer; Radiative forcing; SOA; Temperature dependence; Troposphere; Vertical mixing; Vertical profiles
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2022JD037525

The processes of new particle formation (NPF) and growth are important contributors to cloud condensation nuclei (CCN) concentrations, and CCN are important for climate from their impact on planetary radiative forcing. While the general ubiquity and importance of NPF is understood, the vertical extent and governing mechanisms of NPF and growth in the lower troposphere are uncertain. We present an analysis of four NPF events and two non‐NPF events during the HI‐SCALE field campaign at the Southern Great Plains observatory in Oklahoma, USA. First, we analyzed airborne and ground‐based observations of aerosol and gas‐phase properties. Second, we used a column aerosol chemistry and microphysics model to probe factors that influence the vertical profile of NPF. During HI‐SCALE, we found several instances of enhanced NPF occurring several hundred meters above the surface; however, the spatio‐temporal characteristics of the observed NPF made comparisons between airborne‐ and ground‐based observations difficult. The model represented the observed NPF (or lack of NPF) and particle growth at the surface to final diameters within 10 nm. The model predicted enhanced NPF rates in the upper mixed layer, and this enhancement is primarily due to the temperature dependence in the NPF schemes, but this was also dependent on the vertical profile of gas‐phase precursors measured during HI‐SCALE. We found vertical mixing in the model either enhanced or suppressed NPF rates, aerosol number concentrations, and particle growth rates at the surface. Finally, our analysis provides insights for future field campaigns and modeling efforts investigating the vertical profile of NPF. Plain Language Summary Aerosol particles in the atmosphere are important for climate, weather, and human health. In our work, we are trying to understand some of the processes that create new aerosol particles in the atmosphere. To accomplish this, we looked at measurements of these aerosol particles taken from a measurement site located on the ground and in an airplane. We also looked at some of the different gases in the atmosphere that might contribute to creating, and growing, these new particles. Finally, we took the measurements and put them into a complex aerosol‐chemistry model in order to understand some of the processes “under the hood” that measurements alone cannot tell us. We had to make some educated guesses and assumptions about certain processes in the model; however, we found that the new p