AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Sensitivity of Cloud Droplet Number to Environmental Changes in Aerosol and Cloud Condensation Nuclei (CCN) during the NASA North Atlantic Aerosols and Marine Ecosystems Study (NAAMES)
RICHARD MOORE, Ewan Crosbie, Luke Ziemba, Mary Kacarab, Athanasios Nenes, Gao Chen, Michael Shook, Kenneth Thornhill, Edward Winstead, Bruce Anderson, NASA Langley
Abstract Number: 600 Working Group: Aerosols, Clouds, and Climate
Abstract It has been hypothesized that increased ocean biological activity translates into increased concentrations of submicron aerosol that can be transported over large distances (e.g., O’Dowd et al., Nature, 2004); however, the impact of these aerosols on CCN and the sensitivity of clouds to these aerosols in the local remote marine atmosphere remain highly uncertain. Model simulations suggest that clouds in these remote oceanic regions are highly CCN-limited as compared to continental clouds that are close to aerosol emissions sources (Moore et al., Atmos. Chem. Phys., 2013). Thus, it might be expected that these clouds would be highly sensitive to presence of these biogenic aerosols.
We present airborne in situ measurements of aerosol and cloud microphysical properties and cloud condensation nuclei (CCN) spectra carried out during 2015-2017 as part of the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). These field campaigns target distinct cycles in the annually-occurring North Atlantic phytoplankton bloom, and provide excellent opportunities to examine the influence of biogenic aerosols on CCN and clouds against a backdrop of both the presence and absence of anthropogenic pollution. Aerosol concentrations and cloud droplet number concentrations observed during November were extremely low, and while the addition of aerosol (by ~10-fold) during the Springtime increases cloud droplet number concentrations, the shape of the CCN supersaturation spectrum remains similar between both campaigns. Our interpretation of these findings as well as the cloud droplet sensitivity to aerosols in this unique, pristine regions will be discussed within the context of past airborne campaign datasets.