Bowen ratio
Encyclopedia
In meteorology
and hydrology
, the Bowen ratio is used to describe the type of heat transfer in a water body. Heat transfer can either occur as sensible heat (differences in temperature without evapotranspiration) or latent heat (the energy required during a change of state, without a change in temperature). The Bowen ratio is the mathematical method generally used to calculate heat lost ( or gained ) in a substance; it is the ratio of energy fluxes from one state to another by sensible
and latent
heating respectively. It is calculated by the equation:
where
is sensible heating and 
is latent heating. The quantity 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
. In this context, when the magnitude of
is less than one, a greater proportion of the available energy at the surface is passed to the atmosphere as latent heat than as sensible heat, and the converse is true for values of 
greater than one. As 
, however, 
becomes unbounded making the Bowen ratio a poor choice of variable for use in formulae, especially for arid surfaces. For this reason the evaporative fraction is sometimes a more appropriate choice of variable representing the relative contributions of the turbulent energy fluxes to the surface energy budget.
The Bowen ratio is related to the evaporative fraction,
, through the equation,
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
and hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
, the Bowen ratio is used to describe the type of heat transfer in a water body. Heat transfer can either occur as sensible heat (differences in temperature without evapotranspiration) or latent heat (the energy required during a change of state, without a change in temperature). The Bowen ratio is the mathematical method generally used to calculate heat lost ( or gained ) in a substance; it is the ratio of energy fluxes from one state to another by sensible
Sensible heat
Sensible heat is the energy exchanged by a thermodynamic system that has as its sole effect a change of temperature.The term is used in contrast to a latent heat, which is the amount of energy exchanged that is hidden, meaning it cannot be observed as a change of temperature...
and latent
Latent heat
Latent heat is the heat released or absorbed by a chemical substance or a thermodynamic system during a process that occurs without a change in temperature. A typical example is a change of state of matter, meaning a phase transition such as the melting of ice or the boiling of water. The term was...
heating respectively. It is calculated by the equation:
-
,
where
is sensible heating and is latent heating. The quantity was named by Harald SverdrupHarald Sverdrup
Harald Ulrik Sverdrup was a Norwegian oceanographer and meteorologist who made a number of important theoretical discoveries in these fields. Having first worked in Bergen and Leipzig he was the scientific director of the North Polar expedition of Roald Amundsen aboard the Maud from 1918 to 1925...
after Ira Sprague Bowen
Ira Sprague Bowen
Ira Sprague Bowen was an American astronomer. In 1927 he discovered that nebulium was not really a chemical element but instead doubly ionized oxygen.-Life and work:...
(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
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
and hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
. In this context, when the magnitude of
is less than one, a greater proportion of the available energy at the surface is passed to the atmosphere as latent heat than as sensible heat, and the converse is true for values of greater than one. As , however, becomes unbounded making the Bowen ratio a poor choice of variable for use in formulae, especially for arid surfaces. For this reason the evaporative fraction is sometimes a more appropriate choice of variable representing the relative contributions of the turbulent energy fluxes to the surface energy budget.The Bowen ratio is related to the evaporative fraction,
, through the equation,-
.