On Bouchetʹs complementary hypothesis

Mortonʹs proof of Bouchetʹs complementary hypothesis has been revisited. The proofʹs central assumption is that an increase in sensible heat from the surface to the air induces a similar increment in the sensible heat transfer from the air to a hypothetical potential evaporimeter. It is shown that this assumption is not necessary in the derivation. Instead, the complementary hypothesis under simplified conditions can be obtained with the help of the mass conservation equation for water vapor.