The annual variation in the rotation of the earth, 1951-54.

Abstract

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The annual variation in the rotation of the earth, 1951-54. Markowitz, Wm. Abstract Variations in the rate of rotation of the earth with periods of a year or less can be determined with the aid of quartz-crystal clocks. Solutions were made for each of the three years from September 1951 to October 1954. The astronomical observations were made with the photographic zenith tubes at Washington, D. C., and Richmond, Florida, on a total of over 1500 nights. Two resonator clocks of the National Bureau of Standards, R2 and R3, which had uninterrupted runs, were used. These clocks are of remarkably high precision, and separate solutions were made for each clock. The deviation of either clock from the mean was less than 2 milliseconds for the entire three years. The variation in rotation of the earth was fairly regular from year to year. The earth was about 35 ms fast on October 1 and about 35 ms slow on June 1. Harmonic analysis gives a i-year term of 30 ms amplitude and a 0.5-year term of 10 ms amplitude. There were also found two new terms of about I ms each, which had been predicted. The periods are 13.6 days and 27.6 days, respectively. Values for these four terms were computed by Y. Mintz and W. Munk from meteorological and tidal considerations. The agreement with those given by observation is so good that we may consider the causes of the annual variation to be known. The I-year term, apparently, is due principally to meteorological causes. The 0.5-year term is due principally to the solar tide Ssa and the other two terms are due to the lunar tides Mf and Mm, respectively. Tides affect the moment of inertia of the earth and, hence, its rate of rotation. U. S. Naval Observatory, Washington 25, D. C. Publication: The Astronomical Journal Pub Date: 1955 DOI: 10.1086/107137 Bibcode: 1955AJ.....60Q.171M full text sources ADS |