The stable isotopes of oxygen, hydrogen and others have been used for decades in hydrology, palaeoclimatology, ecology, biogeochemistry etc. The variability of these isotopes in all natural systems have so far been traced back to the climatic imprint on their abundance in precipitation, but the intricacies of the acting processes and mechanisms are still not fully understood. Further, despite water vapor in the atmosphere being the most potent greenhouse gas relatively little is known about the physical processes influencing the absolute content in the atmosphere – that being the fluxes between the atmosphere and the biosphere, cryosphere, hydrosphere, and lithosphere, and the processes during cloud and precipitation formation and between boundary layer and free atmosphere. Furthermore, while present-day observations of stable isotope distribution in precipitation are relatively abundant (at least in parts of the world), they decrease exponentially back in time, making climate reconstructions more difficult and the dependence on modeling results ever increasing. The ability in recent years to make continuous in-situ water vapor isotope observations using spectroscopy analyzers has now made it is now possible to obtain detailed observations of unprecedented quality and quantity. In this context, this session aims to bring together scientists studying the abundance of oxygen and hydrogen stable isotopes in vapor and precipitation and their relationship with climate (and other controlling factors), based on observations and modeling results. We welcome papers dealing with i) present-day observations of oxygen and hydrogen isotopes in vapor and precipitation, ii) contributions in relation to past and present-day modeling experiments, and measurement techniques of vapor and precipitation isotopic composition.