The Contribution of Aerosol Formation and Growth to the Budget of Cloud Condensation Nuclei Observed at the ARM Southern Great Plains Site

Description

Atmospheric aerosol formation and growth is an important environmental nano-scale process, with field measurements and modeling studies indicating that freshly formed particles can contribute significantly to the global population of aerosol and cloud condensation nuclei (CCN). However, our understanding of aerosol formation and growth and its influence on climate is still limited as few ambient measurements have been made of either the formation rate (down to 1 nanometer in diameter) or the initial growth rate of newly formed aerosol clusters (from 1 to 3 nanometers), both of which are necessary to investigate the aerosol formation mechanism and to develop and constrain process-level models. To bridge this gap in understanding, aerosol formation and initial growth were investigated at the ARM Southern Great Plains (SGP) measurement site during the HISCALE field campaign in 2016 and during long-term measurements spanning 2017. Characterization of the aerosol size distribution was accomplished through the deployment of a conventional scanning mobility particle spectrometer, an ultra-high sensitivity aerosol spectrometer, and condensation particle counters of various cut-sizes. Measurements of trace gas precursors included sulfuric acid (during HISCALE IOP2) and sulfur dioxide (during long-term deployment). Aerosol measurements were analyzed to determine the frequency of aerosol formation, the associated aerosol formation and growth rates, and the contribution of newly formed aerosol to the population of potentially CCN-active aerosol. Together with the aerosol measurements, trace gas measurements were analyzed to estimate initial aerosol growth rates, to connect aerosol formation rates to precursor concentrations, and to determine the contribution of precursor species to observed aerosol formation and growth processes.