Water isotope ratios are valuable tracers of atmospheric processes associated with evaporation, condensation and moisture transport. As oxygen and hydrogen have multiple stable isotopes, heavy and light isotopologues of water are unequally partitioned during phase changes. This fractionation of isotopologues provides information on hydrologic processes in the atmosphere at scales ranging from understanding changes in the general circulation of the atmosphere all the way down to condensation within a single cloud. These properties of water isotope ratios make them useful metrics with which to evaluate hydrologic processes within an Earth system model. Moreover, water isotope ratio tracer code in atmospheric models can be extended to trace a wide range of properties associated with evaporation, condensation, and moisture transport, providing further insight into hydrological processes with these models (e.g., Fiorella et al. 2021).

We present progress on implementing isotope ratio and process-oriented water tracers in the next-generation atmosphere model component of E3SM, EAMxx. We also present progress on compiling new model validation datasets from remote sensing platforms as well as precipitation and water vapor measurements from distributed networks, such as the Global Network of Isotopes in Precipitation and the National Ecological Observatory Network.