Harald Sodemann
University of Bergen, Norway


Constraining the sources and transport history of atmospheric water vapour in models


Model simulations of the atmospheric water cycle contain many components that, due to lack of observational constraints, are difficult to validate. Diagnostic methods allow the extraction of properties such as moisture origin, lifetime and transport distance from model data. During precipitation extremes, these quantities can provide insight into the dynamical contributions that amplify an event. However, atmospheric moisture transport pathways and processes rely on model data and thus dependend also on model resolution and parameterisations. A comparison of two complementary approaches to diagnose moisture transport properties for selected events is presented. The Lagrangian diagnostic based on backward trajectories agrees well with the results from the Eulerian method based on water tracers in a regional model. This underpins the validity of the transport scales of water vapour, namely the atmospheric moisture residence time and the transport distance for a particular data set. In order to tie both model diagnostics to reality, stable water isotopes can be employed. The direct interpretation of stable water isotopes is however often complicated by the fact that they represent the integrated atmospheric transport history of water vapour. Using airborne field data from the recent HYMEX campaign in the Mediterranean it is outlined how stable water isotopes can support the interpretation of model-derived scales of water vapour transport.

Time and place
Thursday 1 December 2016, 14.15
Room C609, Arrhenius Laboratory, 6th floor