Characterization of the cloud microphysical and optical properties and aerosol-cloud interaction in the Arctic from in situ ground-based measurements during the CLIMSLIP-NyA campaign, Svalbard

Abstract. This study will focus on cloud microphysical and optical characterization of three different types of episodes encountered during the ground based CLIMSLIP-NyA campaign performed in Ny-Alesund, Svalbard: the Mixed Phase Cloud (MPC), snow precipitation and Blowing Snow (BS) events. These in situ cloud measurements will be combined with aerosol measurements and air mass backtrajectory simulations to qualify and parameterize the arctic aerosol cloud interaction and to assess the influence of anthropogenic pollution transported into the Arctic.

The results show a cloud bimodal distribution with the droplet mode at 10 µm and the crystal mode centered at 250 µm, for the MPC cases. The precipitation cases presents a crystal distribution centered around 350 µm with mostly of dendritic shape. The BS cases show a higher concentration but smaller crystals, centered between 150 and 200 µm, with mainly irregular crystals.

A polluted case, where aerosol properties are influenced by anthropogenic emission from Europe and East Asia, was compared to a clean case with local aerosol sources. These anthropogenic emissions seem to cause higher Black Carbon, aerosol and droplet concentrations, a more pronounced accumulation mode, smaller droplet sizes and a higher activation fraction F_a. Moreover, the activation diameter decreases as the droplet diameter increases and F_a increases showing that smaller particles are activated and droplets grow when the aerosol number decreases. This is in agreement with the first (Twomey) and second (Albrecht) aerosol indirect effect. The quantification of the variations of droplet concentration and size leads to IE (Indirect Effect) and NE (Nucleation Efficiency) coefficients values around 0.2 and 0.43, respectively. These values are close to those found by other studies in the arctic region which confirms these parameterizations of arctic aerosol-cloud interaction in climate models.