Hydrological information in gravity : observation and modelling
Hydrological variations represent significant, broadband, and integral information in temporal gravity observations. On the one hand, they need to be eliminated from high-precision time series as they interfere with small geodynamic signals. On the other hand, they are considered as a valuable supplement to traditional hydrological point measurements. Of particular interest is to what extent such information can be used to improve the understanding of hydrological process dynamics and to evaluate distributed hydrological models. In this context, a new application of temporal gravity observations has been emerging: the study of natural hydrological mass changes and their underlying processes. Interdisciplinary research has been carried out for the hilly and geologically inhomogeneous surroundings of the superconducting gravimeter at the Geodynamic Observatory Moxa, Germany. From repeated gravity observations on a local network as well as combined hydrological catchment and well-constrained gravimetric 3D modelling a high accuracy reduction for the local hydrological signal in the continuous recordings of the superconducting gravimeter was developed. Applying this reduction, the data of the superconducting gravimeter become suitable to be interpreted with regard to changes in continental water storage. Clear global seasonal variations are detected which were previously masked by the local hydrology. This seasonal signal is also found in variations based on global hydrological models and in GRACE satellite observations. The local hydrological model was evaluated. To further enhance its quality and improve the modelled effect of extreme hydrological events such as heavy rain or snow melt, the response time between different storages of the model may be shortened. In general, the methods developed and the results achieved for the surroundings of Moxa observatory can be transferred to other gravity stations and regions worldwide.