Aerosol Fluxes and Boundary‑Layer Coupling in New Particle Formation: Case Studies from the ARM ArcticShark Measurements

RUOYU ZHANG, Fan Mei, Damao Zhang, Yang Wang, University of Miami

     Abstract Number: 213
     Working Group: Aerosols, Clouds and Climate

Abstract
New particle formation (NPF) significantly influences air quality and climate by affecting cloud condensation nuclei (CCN) production. Comprehensive NPF observations have largely been restricted to surface measurements, predominantly reflecting conditions within the lower mixed layer of the planetary boundary layer (PBL). However, emerging research indicates that NPF events may originate at various altitudes above the surface and are potentially linked to PBL dynamics. In this study, we analyzed upper‑PBL aerosol measurements obtained by the DOE ARM uncrewed aerial vehicle ArcticShark at the Southern Great Plains (SGP) observatory. We examined the vertical profile of aerosol properties and developed criteria for flight‑based aerosol flux measurements, which we integrated with PBL and ground‑based aerosol observations to evaluate specific NPF case studies.

From the flight‑based aerosol flux analysis, we found that during NPF periods, turbulence at medium frequency (timescales of 10–15 s) significantly influenced particle fluxes, and instrumentation response frequencies of at least 0.5 Hz were necessary to avoid substantial flux underestimation. Furthermore, a minimum flight‑leg duration of approximately 1,000 s was recommended to accurately capture representative aerosol fluxes when averaging over extended periods. In case study analyses, over half of the observed NPF events originated from higher altitudes. Notably, on May 24, we documented a sustained aerosol particle flux event lasting about 10 minutes, characterized by downward bursts exceeding 1,500 cm⁻³ s⁻¹ originating from the upper PBL. These fluxes were approximately 100–200 times higher than baseline aerosol fluxes recorded during stable atmospheric conditions, indicating significant turbulence‑driven downward transport of nanoparticles. These quantitative findings underscore the critical role of boundary‑layer evolution and upper‑air aerosol dynamics in shaping the vertical distribution and propagation of NPF events.