The Bowen ratio is used to describe the type of heat transfer for a surface that has moisture.
The ratio was named by Harald Sverdrup after Ira Sprague Bowen (1898–1973), an astrophysicist whose theoretical work on evaporation to air from water bodies made first use of it, and it is used most commonly in meteorology and hydrology.
The Bowen ratio is calculated by the equation: In this context, when the magnitude of
becomes unbounded making the Bowen ratio a poor choice of variable for use in formulae, especially for arid surfaces.
, through the equation, The Bowen ratio is an indicator of the type of surface.