Calculate fall speed of an arbitrary ice particle:

Enter temperature [C]:

Enter pressure [hPa]:

Enter maximum dimension of ice particle [microns]

Enter mass of ice particle [micrograms]

Enter area ratio of ice particle [dimensionless]

Click this button to do the sum:

Modified Best number (X*) is:

Reynolds number is:

Fall speed [m/s] is:

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/m2]=1.72x10-5(393/(T[K]+120))*(T[K]/273)1.5

Tool to calculate mass of an ice particle using Brown and Francis:

Enter maximum dimension [microns]:

Click this button to do the sum:

Mass [micrograms] is:

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.

Tool to calculate area ratio of an ice particle using Mitchell (1996):

Enter maximum dimension [microns]:

Click this button to do the sum:

Area ratio [dimensionless] is:

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