High Summertime Aerosol Organic Functional Group Concentrations from Marine and Seabird Sources at Ross Island, Antarctica, during AWARE

Abstract

Abstract.From November 2015 to December 2016, the ARM West Antarctic Radiation Experiment (AWARE) measured submicron 15 aerosol properties near McMurdo Station at the southern tip of the Ross Island. Submicron organic mass (OM), particle number, and cloud condensation nuclei concentrations were higher in summer than other seasons. The measurements included a range of compositions and concentrations that likely reflected both local anthropogenic emissions and natural background sources. We isolated the natural organic components by separating a natural factor and a local combustion factor. The natural OM was 150 times higher in summer than in winter. The local anthropogenic emissions were not 20 hygroscopic and had little contribution to the CCN concentrations. Natural sources that included marine sea spray and seabird emissions contributed 56 % of OM in the austral summer but only 3 % in the austral winter. The natural OM had high hydroxyl group fraction (55%), 6% alkane, and 6% amine group mass, consistent with marine organic composition. In addition, the Fourier transform infrared (FTIR) spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions from natural sources 25 were correlated to incoming solar radiation, indicating that some OM formed by secondary pathways.

Persistent Supercooled Drizzle at Temperatures Below −25 °C Observed at McMurdo Station, Antarctica

“…With the absence of aerosol concentration measurements aloft, and based on the model comparison with the observations, we suggest that the activated N IFN and N A values during the drizzle event should have been on the order of 0.2 L −1 and 20 cm −3 , respectively. These values are within the typical range of McMurdo wintertime N IFN (below −20 °C) and N A from surface‐based reports (Belosi et al, ; Liu et al, ). It is important to note that these number concentrations are rough estimates, because of numerous unexplored degrees of freedom in the model configuration as well as the many uncertainties associated with the comparison of the model results with the observations.…”

The hemispheric contrast in cloud microphysical properties constrains aerosol forcing

“…The latitudinal and seasonal patterns of MODIS N d are supported by the multiyear records of CCN from Antarctic ground sites at King Sejong Station (62°S) ( 47 ) and McMurdo Station (77°S) ( 48 ) ( Fig. 2 and SI Appendix , Fig.…”

“…Seasonal mean sea ice contours from OSTIA fractional sea ice are shown as dashed (1%) and solid blue lines (50%). Locations are shown for McMurdo Station ( 48 ) (solid square) and King Sejong Station ( 47 ) (empty square). The position of the DJF lower tropospheric storm track ( 74 ) is shown with a gray line.…”

“…Satellite-derived N d values in the SO are evaluated using observations from a variety of campaigns and ground stations. In situ CCN observations from McMurdo Station ( 48 ) and King Sejong Station ( 47 ) are drawn from the reported monthly and seasonal mean values in the literature. MODIS N d for these regions is shown averaged across a 4° box centered at the respective stations ( SI Appendix , Fig.…”

Predicting Frigid Mixed‐Phase Clouds for Pristine Coastal Antarctica

“…The seasonal cycle of aerosols is different in the Antarctic region than over the Arctic, as the winter Arctic haze does not have an analog in the Southern Hemisphere, and Antarctic nuclei number concentrations are an order of magnitude larger during summer than winter (Lachlan‐Cope et al., 2020; Liu et al., 2018). An adequate amount of cloud condensation nuclei (CCN) appears to be present to produce common liquid cloud droplet concentrations of 100 cm −3 or greater (e.g., Liu et al., 2018). The persistence of the supercooled liquid at McMurdo as observed by Silber et al.…”