9:30 AM - 9:45 AM
[G04-1-05] Global and regional comparison of hydrological excitation functions of polar motion by GRACE data and climate models
Explaining the hydrological part of the observed polar motion excitation has been a major challenge over a dozen years. The terrestrial water storage (TWS) excitation of polar motion - hydrological angular momentum (HAM), has been investigated widely using global hydrological models, mainly at seasonal timescales. However, the results from the models do not agree among themselves and do not fully explain the role of hydrological signal in polar motion excitation. Throughout the past decade, the Gravity Recovery and Climate Experiment (GRACE) has given an unprecedented view on global variations in TWS.
Our investigation is focused on the influence of Terrestrial Water Storage (TWS) variations obtained from Gravity Recovery and Climate Experiment (GRACE) satellite mission as well as from hydrological and climate models on polar motion excitation functions at decadal, inter-annual and seasonal timescales. The global and regional trend, seasonal cycle as well as some extremes in TWS variations are considered here.
Here TWS are obtained from the monthly mass grids land GRACE Tellus data: GRACE CSR RL05, GRACE GFZ RL05 and GRACE JPL RL05. As a comparative dataset, we also use TWS estimates determined from the World Climate Research Programme's Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models and Global Land Assimilation Data System (GLDAS) hydrological models. The TWS is estimated in two ways: firstly, as a difference of total precipitation, evapotranspiration and total water runoff and secondly, as the sum of soil moisture in all layers, accumulated snow, and plant canopy surface water.
Our studies include two steps: first, the determination and comparisons of regional patterns of TWS obtained from GRACE data, climate and hydrological models, and second, comparison of the regional and global hydrological excitation functions of polar motion with a hydrological signal in the geodetic excitation function of polar motion.
Our investigation is focused on the influence of Terrestrial Water Storage (TWS) variations obtained from Gravity Recovery and Climate Experiment (GRACE) satellite mission as well as from hydrological and climate models on polar motion excitation functions at decadal, inter-annual and seasonal timescales. The global and regional trend, seasonal cycle as well as some extremes in TWS variations are considered here.
Here TWS are obtained from the monthly mass grids land GRACE Tellus data: GRACE CSR RL05, GRACE GFZ RL05 and GRACE JPL RL05. As a comparative dataset, we also use TWS estimates determined from the World Climate Research Programme's Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models and Global Land Assimilation Data System (GLDAS) hydrological models. The TWS is estimated in two ways: firstly, as a difference of total precipitation, evapotranspiration and total water runoff and secondly, as the sum of soil moisture in all layers, accumulated snow, and plant canopy surface water.
Our studies include two steps: first, the determination and comparisons of regional patterns of TWS obtained from GRACE data, climate and hydrological models, and second, comparison of the regional and global hydrological excitation functions of polar motion with a hydrological signal in the geodetic excitation function of polar motion.