Seasonal polar motion excitation from numerical models of atmosphere, ocean, and continental hydrosphere

Abstract

[1] Effective angular momentum functions from atmosphere, oceans, and terrestrial water storage are obtained from European Centre for Medium-Range Weather Forecasts atmospheric data and corresponding simulations with the Ocean Model for Circulation and Tides and the Land Surface and Discharge Model (LSDM). Mass exchanges among the subsystems are realized by means of freshwater fluxes, causing the total ocean mass to vary predominantly annually. Variations in total ocean mass affect the oceanic excitations of the annual wobble by almost 1 milliarc second (mas) for both prograde and retrograde components, whereas the motion term contributions of terrestrial water flow derived from LSDM are found to be 3 orders of magnitude smaller. Since differences to geodetic excitations are not substantially reduced and regional decompositions demonstrate the large spatial variability of contributions to seasonal polar motion excitation that compensate each other when integrated globally, it is concluded that the closure of the seasonal excitation budget is still inhibited by remaining model errors in all subsystems.Citation: Dobslaw, H., R. Dill, A. Grötzsch, A. Brzeziński, and M. Thomas (2010), Seasonal polar motion excitation from numerical models of atmosphere, ocean, and continental hydrosphere,

Determination of the Earth's pole tide Love number k2 from observations of polar motion using an adaptive Kalman filter approach

“…The previously applied atmosphere/ocean model combination NCEP/ECCO is replaced by atmosphere and ocean data from ECMWF (European Centre for Medium-Range Weather Forecasts) and OMCT (Ocean Model for Circulation and Tides). Respective variations of I(t) and h(t) were computed from ECMWF and OMCT effective angular momentum functions (see Dobslaw et al [2010] for details).…”

Monthly Crustal Loading Corrections for Satellite Altimetry

“…Boy (University of Strasbourg). Time-varying ocean mass is modeled with the Ocean Model for Circulation and Tides (OMCT) product (Dobslaw and Thomas 2007), which is supplied by the GRACE project team at GeoForschungsZentrum, Potsdam, Germany. OMCT is a 3D primitive equation ocean model forced by wind stress, atmospheric surface pressure, temperature, and freshwater fluxes from 6-h ECMWF operational analyses.…”

Observations of stratospheric sudden warmings in Earth rotation variations

“…For example, the seasonal variation in the extratropical tropospheric jets causes a change in the axial relative AAM, which causes the length of day to fluctuate by about 1 ms every year [Hide et al, 1997]. Likewise, the annual appearance of the Siberian high-pressure system causes a yearly fluctuation in the two equatorial components of AAM, which results in a polar wobble of several mas [Chao and Au, 1991;Nastula et al, 2009;Dobslaw et al, 2010].…”

“…All Rights Reserved. subseasonal time scales the atmosphere is the dominant source of axial angular momentum [Rosen and Salstein, 1983;Eubanks et al, 1985] and a major source, along with the ocean, of equatorial angular momentum [Dobslaw et al, 2010].…”