Dear authors

One comment on page 6824 line 7-11: "Until recently, SOM was modeled as a low-viscosity liquid into which gas-phase species from the surrounding environment diffused quickly ... lower than would be consistent with a liquid material"

For the completeness, I would suggest to mention the “less solid” nature of sub-30 nm particles and potential influence of particle size and oxidation station on the viscosity of SOM (Saukko et al., 2012;Cheng et al., 2015).

Congratulations on your manuscript proceeding to ACP.

Best wishes,

Hang

Reference:

Saukko, E., Lambe, A. T., Massoli, P., Koop, T., Wright, J. P., Croasdale, D. R., Pedernera, D. A., Onasch, T. B., Laaksonen, A., Davidovits, P., Worsnop, D. R., and Virtanen, A.: Humidity-dependent phase state of SOA particles from biogenic and anthropogenic precursors, Atmos. Chem. Phys., 12, 7517-7529, 10.5194/acp-12-7517-2012, 2012.

Cheng, Y., Su, H., Koop, T., Mikhailov, E., and Pöschl, U.: Size dependence of phase transitions in aerosol nanoparticles, Nat Commun, 6, 10.1038/ncomms6923, 2015.