Properties of cloud condensation nuclei, ice nucleating particles, and cloud particle residuals in and around clouds of the Southern Ocean (HALO 2024, HALO-South)

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The Southern Hemisphere (SH) and particularly the Southern Ocean (SO) are locations on Earth which are understudied concerning atmospheric and specifically cloud related properties. Furthermore, over the SO, models such as general circulation models (GCMs) cannot correctly reproduce cloud coverage, cloud phase and atmospheric aerosols, although these are important parameters for the assessment of anthropogenic aerosol impacts and cloud feedbacks on climate. Compared to models, satellite data show higher fractions of supercooled liquid water in clouds in the SH, particularly over the SO, causing a radiation bias and hence errors in models estimating the radiation budget of the earth-atmosphere system. Aerosol particles in general, and cloud condensation nuclei (CCN) and ice nucleating particles (INP) in particular, influence cloud formation and glaciation, respectively, thereby affecting cloud microphysical and radiative properties. Information concerning the properties, as well as indications and hypotheses with respect to potential sources of aerosol particles in general, and CCN and INP, in particular, over the Southern Ocean do exits. However, both amount of data and quantitative process understanding are not sufficient for driving, evaluating, and even more important improving atmospheric models over the SO region. Therefore, in the framework of this proposal, we suggest the combined measurement of CCN, INP, and cloud particle residual properties, together with a thorough evaluation of their respective origins and sources. Applied instruments are a miniaturized Cloud Condensation Nucleus Counter (mCCNc), the high-volume flow aerosol particle filter sampler (HERA) and a Counterflow Virtual Impactor (HALO-CVI).