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- Title
Atmospheric angular momentum and the length of day: a common fluctuation with a period near 50 days.
- Authors
Langley, Richard B.; King, Robert W.; Shapiro, Irwin I.; Rosen, Richard D.; Salstein, David A.
- Abstract
Semiannual, annual and some longer period changes in the rotation of the Earth have long been attributed to meteorological causes1-3. More recently some higher frequency variations in the length of day (l.o.d.) were shown to be strongly correlated with variations of the polar component of the angular momentum of the atmosphere4,5. However, fluctuations in l.o.d. with periods near 50 days were not definitely identified, because either the sampling was too coarse4 or it extended over too short an interval5. Fluctuations in tropical wind speeds with periods in this range have, nevertheless, been studied4,6,7, but their counterparts, although expected4, had not been identified in the Earth's rotation. Last year, four astronomical measures of changes in l.o.d. obtained in 1979 were shown to exhibit nearly the same ∼50-day fluctuation8. To find out whether this fluctuation was persistent and of meteorological origin we analysed lunar laser ranging (LLR) observations from the McDonald Observatory in Texas and zonal (east-west) wind data deduced from sources distributed over the globe. The relevant data were available for the common period 1976-79. We describe these analyses in turn and then compare the results.
- Publication
Nature, 1981, Vol 294, Issue 5843, p730
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/294730a0