Boundary Layer Gradients in New Particle Formation and Growth at Southern Great Plains

New particle formation followed by growth is a major source of cloud condensation nuclei

cloud condensation nuclei

Tiny airborne particles suspended in the atmosphere that serve as the seeds around which cloud droplets form.

Source: Source

and thus impacts our understanding how aerosols

aerosols

Small particles or droplets, such as wildfire smoke, volcanic gases, or salty sea spray, that float in the air. They are emitted by both natural events and human activities.

Source: NASA Global Climate Change Source

affect cloud lifecycle, properties, and processes. New particle formation and growth are known to occur throughout the troposphere, however, much of our knowledge of these processes is derived from surface-based measurements. Although few measurements of the vertical distribution of new particle formation and growth exist, emerging evidence from the available measurements suggests that the processes occur heterogeneously throughout the boundary layer. Moreover, the existing measurements highlight a critical need for additional measurements that probe both the vertical distribution of new particle formation and growth and the detailed chemical characteristics of the surface layer.

Here, we propose to connect ground-based measurements of atmospheric chemical composition and aerosol size distribution to vertically resolved measurements of 1-3 nm aerosol cluster concentration and meteorology. This project leverages existing measurements from fall (October 2021) and spring (April 2022) measurements at the Department of Energy Atmospheric Radiation Measurement Southern Great Plains user facility and will make new measurements involving the coordinated deployment of the tethered balloon system and surface-based instrumentation capable of measuring critical parameters for new particle formation and growth (i.e., sulfuric acid and highly oxidized organic molecules). The central hypothesis guiding this work is that new particle formation and growth at this site are modulated by vertical gradients that exist within the boundary layer, including gradients within the mixed layer. These critical measurements and analysis are needed: [1] because particle formation aloft followed by transport of grown particles to the surface may be a significant contribution to the cloud condensation nuclei budget, [2] to connect the atmospheric conditions that drive atmospheric particle formation with boundary layer processes and meteorology, and [3] to evaluate the extent to which surface-based aerosol measurements are representative of the atmospheric aerosol aloft.  Insights gained from the proposed work will ultimately contribute to improving our process-based understanding of aerosol processes that affect clouds.