Condensation particles (CP) comprise all atmospheric particles which can act as nuclei for condensation of low volatile gaseous compounds like organic species (biogenic or from any combustion process), organic and mineral acids which are both reaction products of atmospheric photooxidation processses and most notably water vapour. Generally particles >3 nm in diameter can act as condensation nuclei. Especially particles within the accumulation mode (particle diameter 0.1-2.5 µm) can act as efficient cloud condensation nuclei and play an important role in cloud formation. The latter fact emphasizes the crucial role of aerosols in determining atmospheric radiation transfer. CP concentrations at Neumayer exhibit a stepwise increase from polar winter (below 100 particles cm-3) to a maximum in late austral summer of around 1000 particles cm-3.
During summer the chemical composition of these particles is mainly MSA and nss-sulfate, thus CN are formed in the marine troposphere by photooxidation of DMS emitted by the phytoplankton. During winter and stormy weather conditions, however, sea salt dominates the aerosol mass. Interestingly, the maximum of condensation particle concentration typically appears in late February to early March, i.e. shifted by around 4-6 weeks compared to the MSA and nss-sulfate maxima. Our measurements suggest that during late summer the concentration of very small particles between 3-5 nm diameter (nucleation mode) is significantly enhanced, indicating new particle formation. DMS could act via its photooxidation product sulphuric acid as gaseous precursor for nucleation mode particles, a process known as gas to particle conversion.
Due to the relatively short atmospheric lifetime (a few hours) of nucleation mode particles, regional sources should dominate the measured signal. We believe that following the retreat of sea-ice in the nearby Atka Bay during late February, considerable amounts of DMS are released by the now emerging phytoplankton bloom in this area. Note that nucleation mode particles do not contribute much to the total aerosol mass due to their small size, therefore nss-sulfate and MSA concentration maxima do not necessarily coincide with the particle number concentration maximum! Details regarding the sampling method can be found here...
As an example, the particle size distribution in the range between 0.005 µm and 5 µm throughout the year 2018 is shown in the contour plot below. Put in a nutshell, austral summer is dominated by higher total aerosol number concentrations with mean particle diameters around 0.1 µm (mainly biogenic sulphur aerosol, i.e. non sea salt sulphate and methanesulphonate), while during polar night, very often larger particles (predominantly sea salt aerosol) between 200 nm and 2 µm, but lower total number concentrations are typical. The figure shows a 3D contour plot of the particle size distribution dN/dlogDp (cm-3) with a dlogN/dlogDp (cm-3) scale as z-axis (logarithmic colour scale to the right). Presented data are one-hour averages based on the originally size distribution spectra taken in 10-minute intervals; doy is day of the year 2018. Details regarding the sampling method can be found here. Data archived in PANGAEA are available here: for Scanning Mobility Particle Sizer (SMPS) and Laser Aerosol Spectrometer (LAS3340).
To give an impression on the dynamics of the size distribution, see this short video animation. Presented are the particle size distributions in the range from 5 nm to 5000 nm (0.005 µm to 5 µm; measured by the SMPS (blue) and LAS3340 (red); size resolution 64 bins per decade) in a double logarithmic plot for the period 1. January 2022 (doy = 1) through 28. April 2022 (doy = 118).
Weller, R., A. Minikin, D. Wagenbach, and V. Dreiling, Characterization of the inter‑annual, seasonal, and diurnal variations of condensation particle concentrations at Neumayer, Antarctica. Atmospheric Chemistry and Physics., Copernicus Publications, 11, pp. 13243‑13257. doi: 10.5194/acp‑11‑13243‑2011, 2011.
Weller, R., Schmidt, K., Teinilä, K., and Hillamo, R.: Natural new particle formation at the coastal Antarctic site Neumayer, Atmos. Chem. Phys., 15, 11399-11410, doi:10.5194/acp-15-11399-2015, 2015.