Abstract View
Turbulent Flux Measurements of the Near-surface and Residual-layer Nucleation Particles
NICHOLAS MESKHIDZE, Markus Petters, Mohammad Maksimul Islam, North Carolina State University
Abstract Number: 245
Working Group: Aerosols, Clouds and Climate
Abstract
New particle formation (NPF) events have been observed at various locations over the world. The main objective of the field campaign that was conducted at the DOE ARM SGP site in Oklahoma from 15 Oct. to 15 Nov. 2020, was to examine the feasibility to use the eddy-covariance flux measurement of >3 and >10 nm particles to distinguish between ground-level and residual-layer NPF events. Equipment deployed include a 10-m telescopic tower, multiple condensation particle counters, a sonic anemometer, an SMPS and POPS (for aerosol number size distribution from 10 to 300 nm and 180 nm to 3 mm, respectively), an HTDMA (for 15, 20, 30, 40, and 50 nm-sized particle hygroscopicity), and a mini SODAR (for wind profiles between 15 and 500 m).
Here we report results showing data of eddy-covariance particle flux superimposed with observed small particle events. Seven small particle events (defined as periods where 3 to 10 nm-sized particle number concentrations increased by greater than one order of magnitude above the background) were observed. Downward vertical turbulent fluxes of sub-10 nm-sized particles generally coincided with the small particle events, suggesting that the majority of the new sub-10 nm particles observed at the surface during the event originated aloft and were brought to the surface by convective mixing during the daytime evolution of the planetary boundary layer. Hygroscopic growth factor measurements indicated growth factors much smaller than those of ammonium sulfate, suggesting that organic compounds dominated the sub-50 nm sized particle chemical composition. Results of our study show that eddy covariance vertical turbulent flux measurements of 3 to 10 nm sized particles can provide an important constraint and help to understand the formation, origin, and evolution of nucleation mode particle number concentration and size distributions during ground-based observational campaigns.