Curvature Effect and Terminal Velocity in Cloud Droplets

Droplet Diameter [μm]

Relative Humidity for Droplet  Equilibrium* [%]

Terminal Velocity [m/s]

Required Time
to Fall 1.0 Meter

Type of Droplet

¥ 100.00 11 0.091 sec Larger than rain
100 100.00 0.27 3.7 sec Large Cloud
20 100.01 0.01 1 min 40 sec Typical
10 100.04 0.003 5.6 min  
2 100.1 0.0001 2.8 hr Small
1 100.2 0.00003 9.3 hr  
< 1 Increases rapidly with decreasing droplet size

           < 0.00003

 > 9.3 hr Tiniest

  *The relative humidity data are plotted in Table 7.3 on page 167 of the text.