Toward a Mechanistic Understanding of d-Excess as a Tracer for Evapotranspiration

An understanding of atmospheric water vapor content and its isotopic composition is important if we are to be able to model future water vapor dynamics and its potential feedbacks on future climate change. Here I investigate near-surface processes that influence the isotopic variation of water vapor. A simple water isotopologue mass balance model was developed to quantify diel changes in the deuterium-excess (d-excess) of the water vapor. Discussion include the need of a regular calibration procedure for in-situ, high resolution water vapor isotope ratio measurements using optical spectroscopy analyzers.