Deuterium and oxygen-18 in precipitation and other natural waters Some theoretical considerations

In the paper an attempt is made to express the isotope concentration in precipitation as a function of the atmospheric process which transport water vapor. It is found that the fractionation which takes place is considerably less when the atmospheric transport is due to eddy motion than when transport is simply advective. In the latter case fractionation follows the Rayleigh condensation formula. In the case of eddy transport fractionation may under special circumstances follow the same formula although with a factor (√α − 1) instead of (ɑ − 1). More complicated transport patterns in the atmosphere are rather difficult to express mathematically.As to the vertically integrated transport it is at present difficult to derive explicit relations over ocean areas because of the exchange which takes place between air and water. Over continents, however, the relation can be formulated more explicit under certain conditions.Available data show a general relation between oxygen-18 and precipitable water which indicates that eddy transport is of major importance for distributing water vapor in the atmosphere.As to isotope concentrations in surface waters, exchange of water between air and liquid water is rather important and cannot be neglected in cases where data are applied to specific hydrologic problems.