MOTIV (MOisture Transport and Isotopologues of water Vapour) is funded by the DFG (Deutsche Forschungsgemeinschaft) as a collaborative project between Germany and Switzerland (in the context of the D-A-CH programme with DFG being the Lead Agency). The Swiss project partner is a group at the ETH Zürich (https://www.iac.ethz.ch/group/atmospheric-dynamics.html). The aim of MOTIV is to establish tropospheric water vapour isotopologues as an observational tool for testing the model representation of atmospheric moisture pathways.