Flat versus Curved Water
Surfaces
 given flat and curved water
surfaces where the air adjacent to each is
saturated >>
 more energy is required to
maintain the "curvature" of
the drop
 therefore, the water
molecules on the surface of the drop have more
energy
 therefore, they evaporate
more readily that from the flat water surface (compare the length of
the red arrows)
 therefore: evaporation rate
off curved surface > evaporation rate off of
flat surface
 since air above both surfaces is
saturated, then
 evaporation
rate = condensation rate
 therefore, condensation rate
onto droplet > condensation rate onto flat
water surface
 therefore, e_{sdrop}
> e_{sflat}
 therefore:
 if RH_{flat} =
100%, then RH_{drop} > 100%
 the air surrounding the
drop must be supersaturated!!
 This is called the curvature effect

