This study presented the long-term measurement results of particle number size distribution, CCN, chemical composition and hygroscopicity at an island observatory in Southeast Atlantic. It highlights how the biomass burning, sea salt aerosols influencing the particle hygroscopicity, as well the relationship between meteorological parameters, providing valuable datasets and scientific insights in understanding the aerosol-cloud interaction in marine boundary layer. This paper is well prepared. However, more robust analysis and comprehensive data are needed to enhance the credibility of the conclusion. For example, as there are a lot assumptions made to derive k values, why not use the chemical composition date to calculate a κ to constrain your method. More detailed comments are given below:

1. In section 2.1, please listed all the instrument model and manufacture in the experiment setup.
2. Line 100, the size range of SMPS is 10-500 nm, but you derive PNSD of 3-1000 nm by extrapolation, that will cause large bias especially on new particle formation cases. I think the comparison between 10-500 nm and 3-1000 nm is necessary. And with the large discrepancy caused by dp<10 nm and dp>500 nm, the reason should be analyzed and make sure if the extrapolation is reasonable. Otherwise, I recommend only 10-500 nm should be discussed.  
3. In section 2.2, it shows the CCN at ss of 1% was 30% higher than SMPS, it the counting efficiency of CPC is 1?
4. Figure 1. Would you please lower down the x- and y- axis to (0, 0), which helps to know if the blues dots at the bottom are zero. The zero data doesn’t make sense.
5. As you mentioned you also have ACSM measurement, why don’t you use chemical composition to estimate κ , or validate the method you modified?
6. In section 3.1, would you please give more detailed information about the mass fraction of sulfate corresponding to the extremely low and high κ , such as 0.3 and 0.78?
7. It is recommend giving the time series or the means of CCN and PNSD, as well as BC, for the both campaign in 2016 and 2017, respectively, to make the readers easily understood the general aerosol background level. It could be provided in the supplementary materials. As the observatory get more influence from sea salt aerosols in 2017, does the PNSD shifted to larger size as compared that of 2016?
8. In section 3.6, as the authors analyzed how the meteorological factors influencing the BB and sea salt transport, have you exclude the influence by precipitation?

Please find my full review report in th eattached file.