function critical_radius_ice,T,S ;----------------------------------------------------------------------------- ; Compute the critical radius, which is the smallest radii for a particle to ; exist under the input conditions. The expression is for ice particles from ; Rapp & Thomas [JASTP, 2006] ; ; In: ; T......temperature (K) ; S......saturation ratio (unitless) ; ; Out: ; rc....critical radius (nm) ; ; Source: Mark Hervig ;----------------------------------------------------------------------------- ;- some constants Bc = 1.380662e-23 ; Boltzmans constant, J/K Sti = 0.122 ; surface tension of ice in the presence of air, J/m2 Di = 0.93e6 ; ice density, g/m3 Mww = 18.0 ; molecular weight of H2O, g/mol Mwm = Mww*1.66056e-24 ; mass of h2o molecule, g ;- critical radius from Rapp & Thomas [2006] rc = 1e9 * 2. * Mwm * Sti / (Bc * T * Di * alog(S) ) ; nm ;- done return,rc end