In Mason's formulation the changes in temperature across the boundary layer can be related to the changes in saturated vapour pressure by the Clausius–Clapeyron relation; the two energy transport terms must be nearly equal but opposite in sign and so this sets the interface temperature of the drop.
In Mason's framework, variations in temperature across the boundary layer are associated with changes in saturated vapour pressure through the Clausius–Clapeyron relation; the two energy transport components must balance each other out but have opposite signs, thus setting the interface temperature for the drop.