Abstract View
Effects of Cloud Conditions on Particle Size Distributions in the Southeast US
STEPHEN NOBLE, Savannah River National Laboratory
Abstract Number: 211
Working Group: Aerosols, Clouds and Climate
Abstract
Clouds can alter atmospheric particle concentrations and size through physical and chemical processing. This aerosol-cloud interaction is understudied but has implications for short wave cloud albedo. Bimodal distributions associated with cloud processing are prevalent in the marine environment (Hoppel et al. 1986; Hudson et al. 2015). Clouds have also been shown to influence particle size distributions (PSD) in continental air masses at the Southern Great Plains site in the central US (Noble & Hudson 2019). In the Southeastern US where influences from both maritime and continental airmasses are prevalent, PSDs were measured using a Scanning Particle Mobility Sizer at the Savannah River Site (near Aiken, SC). Preliminary data show PSDs vary with differing conditions. Bimodal PSDs with lower concentrations and larger accumulation mode sizes were found with persistent status clouds with cloud bases near 600 m above ground level. During a period of scattered shallow cumulus clouds with bases near 1100 m, PSDs were found to be only slightly bimodal with smaller accumulation mode sizes and higher total concentrations. PSD taken during clear skies showed the highest PSD total concentrations with a single mode peaking in the Aiken range (<100 nm). These measurements are consistent with Noble & Hudson (2019) which found PSDs associated with high cloud fractions and low cloud bases had reduced total concentrations, larger mean sizes, and increased concentrations in the accumulation mode. Thus, cloud processing of aerosols through widespread aerosol-cloud interactions is not limited to the marine environment. The tendency of clouds to modify particles that act as cloud condensation nuclei impacts subsequent cloud formation and cloud radiative properties.
[1] Hoppel, W.A., Frick, G.M., & Larson, R.E. (1986). GRL, 13(2), 125–128.
[2] Hudson, J.G., Noble, S., & Tabor, S. (2015). JGRA, 120, 3436–3452.
[3] Noble, S.R., & Hudson, J.G. (2019). JGRA, 124, 5479–5502.