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Diurnal atmosphere‐ocean signals in Earth's rotation rate and a possible modulation through ENSO
Author(s) -
Schindelegger M.,
Salstein D.,
Einšpigel D.,
Mayerhofer C.
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl072633
Subject(s) - geodetic datum , earth's rotation , troposphere , angular momentum , diurnal cycle , physics , geodesy , atmospheric sciences , polar motion , climatology , inversion (geology) , geophysics , geology , environmental science , meteorology , classical mechanics , seismology , tectonics
Abstract Space geodetic determinations of a 6 μs length‐of‐day (LOD) anomaly at the diurnal S 1 frequency are reconciled with excitation estimates from geophysical fluid models. Preference is given to a hybrid excitation scheme that combines atmospheric torques with oceanic angular momentum (OAM) terms from hydrodynamic forward modeling. A joint inversion of all data sets yields an LOD in‐phase and quadrature estimate of (5.91, −0.22) μs, matching space geodetic S 1 terms well within their formal uncertainties. Non‐harmonic LOD excitations, while less than 30% of the time‐averaged rotation rate contribution, are conclusively linked to El Niño–Southern Oscillation (ENSO) as the main perturbation of diurnal cycle characteristics in the troposphere. ENSO modulations of particular relevance are those in OAM, associated with the barotropic ocean response to regional modifications in the diurnal atmospheric pressure wave. The study thus highlights previously unexplored aspects of non‐tidal mass‐field variability in the Earth system.