Dear authors,

I’m glad to accept your article for final publication in ACP. One minor comment from mys side concerning the last comment of reviewer #4 about the influence of hygroscopic growth. Here I like to add some experience from my own research. Below 40% RH, particles can and most probably will contain water which significantly may contribute to the overall particle light scattering properties. We have seen this at several of our measurements using a humidified nephelometer in the field (see e.g. Fig. 5 in Zieger et al., 2013 or Fig 1a in Zieger et al., 2014). Even pure inorganic sea salt will contain significant amounts of water at apparently “dry” conditions (see Fig. 2a and 2b in Zieger et al., 2017). This also means that they are more spherical rather than cubical, which may be relevant for your retrieval as well. In addition, the RH history of the particles has to be considered due to the hysteresis effects. Thus I would recommend to soften this statement in your final manuscript. Maybe also mention the average RH values inside your scattering cell.

Kind regards,

Paul.

Zieger et al., 2017: https://www.nature.com/articles/ncomms15883
Zieger et al., 2014: http://www.tandfonline.com/doi/abs/10.3402/tellusb.v66.24536
Zieger et al., 2013: https://www.atmos-chem-phys.net/13/10609/2013/

Dear authors,

Thanks for your fast response. I'm happy to accept your manuscript for final publication in ACP.

Kind regards

Paul.