Validation of Mpi-Esm Decadal Hindcast Experiments with Terrestrial Water Storage Variations As Observed By the Grace Satellite Mission

Time-variations in the gravity field as observed by the GRACE mission launched in 2002 provide for the first time quantitative estimates of the terrestrially stored water masses at monthly resolution over more than one decade. TWS from GRACE is applied here to validate different sets of ensemble hindcasts performed with the coupled climate model MPI-ESM that have been prepared within the German Research Initiative on Decadal Climate Prediction (MiKlip) during recent years.

Moderately positive skill scores of the initialized hindcasts are obtained both with respect to the zero anomaly forecast and the uninitialized projections in particular for leadyear 1 in particular in moderate to high latitudes of the Northern Hemisphere. Skill scores gradually increase when moving in more recent experiments and also for experiments performed at higher spatial resolution, thereby documenting improvements of the MPI-ESM decadal prediction system during course of the Miklip project.

Analyses indicate that the skill changes obtained here reflect in particular changes in the large-scale precipitaiton pattern between the individual experiments, which itself is an important target quantity of the climate prediction. We will explain in this talk how GRACE-based TWS might contribute to the validation of precipitation changes in particular in regions of the world where reliable in-situ observations are sparse.