Atmosphere-Hydrosphere Dynamics

This topic focuses on the numerical simulation of transient dynamics and their complex interactions in atmosphere, oceans, cryosphere, and continental hydrosphere generally accompanied by mass, momentum, and energy transports within and exchanges between the individual subsystems. Signatures of these processes are routinely observed by means of various geodetic and geophysical observation techniques. In combination with the observed variability patterns (e.g., of the time-variable gravity and magnetic fields, seismic tomography images, surface deformation, sea-level variations and Earth orientation parameters), complementary model approaches are used to identify underlying physical processes and, consequently, to allow for broad interpretations of the global monitoring data principally reflecting the Earth’s response to a superposition of various processes in various subsystems caused by external and internal forces. The time scales of interest range from sub-daily to decadal, enabling the investigation of global change phenomena and their regional impact, such as sea-level rise, water resources, and the coupling of geomagnetic field variations with oceanic processes.

The surface model system will be complemented by model approaches for solid Earth dynamics providing a link between these subsystems at different time scales, such as a global thermomechanical ice-sheet model for present time ice-mass change including interactions with ocean circulation models.

The present version of the near-surface model system is based on the model combination ECMWF-OMCT (Ocean Model for Circulation and Tides) currently in use as background model within the standard GRACE de-aliasing procedure and on the Hydrological Discharge Model (HDM, "Earth System Model"). Atmospheric and oceanic mass anomalies derived from this model approach are calculated routinely with 3 days latency and are delivered to the GRACE project via ISDC data portal in order to minimize aliasing of short-term mass variations into monthly mean gravity fields "Geotechnologien II". Mass redistributions in atmosphere, oceans, and continental hydrosphere also affect rotational parameters of the Earth, i.e., polar motion and length of day FOR 584, project 2/ project 10, "Earth System Model").
Changes in Earth’s rotational parameters due to oceans are not only created by oceanic mass redistributions, but also by changes in oceanic currents (e.g. by tides).
Further advancements of the OMCT, by means of assimilation methods, will not only increase the model’s accuracy and forecasting ability, but will also allow more accurate calculation of mass- and motion terms of the oceanic angular momentum, by bringing the model closer to observational data.


Contact: Prof. Dr. Maik Thomas; Dr. Henryk Dobslaw