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Long-Period Tidal Variations in the Length of DayA new model of long-period tidal variations in length of day is developed. The model comprises 80 spectral lines with periods between 18.6 years and 4.7 days, and it consistently includes effects of mantle anelasticity and dynamic ocean tides for all lines. The anelastic properties followWahr and Bergen; experimental confirmation for their results now exists at the fortnightly period, but there remains uncertainty when extrapolating to the longest periods. The ocean modeling builds on recent work with the fortnightly constituent, which suggests that oceanic tidal angular momentum can be reliably predicted at these periods without data assimilation. This is a critical property when modeling most long-period tides, for which little observational data exist. Dynamic ocean effects are quite pronounced at shortest periods as out-of-phase rotation components become nearly as large as in-phase components. The model is tested against a 20 year time series of space geodetic measurements of length of day. The current international standard model is shown to leave significant residual tidal energy, and the new model is found to mostly eliminate that energy, with especially large variance reduction for constituents Sa, Ssa, Mf, and Mt.
Document ID
20160005756
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ray, Richard D. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Erofeeva, Svetlana Y. (Oregon State Univ. Corvallis, OR, United States)
Date Acquired
May 3, 2016
Publication Date
February 27, 2014
Publication Information
Publication: Journal of Geophysical Research: Solid Earth
Volume: 119
Issue: 2
ISSN: 2169-9313
Subject Category
Geosciences (General)
Report/Patent Number
GSFC-E-DAA-TN21215
GSFC-E-DAA-TN31861
Distribution Limits
Public
Copyright
Other
Keywords
LOD tidal oscillations
tidal variance
anelastic mantle effects