Based on the parameterisation of Heymsfield and Westbrook (2010) *J. Atmos. Sci.* **67** 2469-2482.

Air density estimated using ideal gas law for dry air.

Dynamic viscosity computed from temperature using the correlation: viscosity [Ns/m^{2}]=1.72x10^{-5}(393/(T[K]+120))*(T[K]/273)^{1.5}

using relationship of Brown and Francis (1995) JTech. **10** 579-590. Note that technically this study actually uses an 'average' diameter rather than maximum dimension, but most people apply it using maximum dimension anyway (as I am here). The original relationship comes from Locatelli and Hobbs (1974, JGR) who used the maximum dimension of the particle when it had settled onto a slide at the ground.

using the relationship for polycrystals/aggregates in table 1 of Mitchell (1996) * J. Atmos. Sci * **53** 1710-1723