大気圧による極運動励起について

抄録

The excitation functions for the Earth's polar motion due to the variation of the atmos pheric pressure distribution are calculated from the three kinds of materials, labeled here by A, B and C, of the meteorological data which were published by the Japan Meteorological Agency. The material A has the normals of the monthly atmospheric pressure at the mean sea level for both of the northern and southern hemispheres. Its average year values in latitude range 80°N-0° are taken over the period 1881-1935 and those in latitude range 0-60°S over the period 1931-1960. The material B has the average year values of the monthly atmospheric pressure in the northern hemisphere (80°N-10°N), which are taken over the true periods 1909-1914 and 1924-1937. The material C includes the monthly mean values of the atmospheric pressure at the mean sea level and the height of the isobaric surface of 500 mb from 1947 Mar. to 1975 Feb. in the northern hemisphere with mesh interval 10° in both of latitude and longitude. It turns out that the excitation function can be fairly described by the data of the atmospheric pressure on only the northern hemisphere. The amplitude of the annual component of the excitation function shows the secular variation with the rate of 0.1610×10⁰ radian/yr.. The turning points of the annual change in summer appear almost stationarly on July, but the turning point in winter varies from year to year ranging from November to February and the double peaks appear over about one third of years with data. The differential excitation function on each latitude zone with mesh 10° shows irregular variations at the higher latitude zone while stable annual changes at the lower latitude zone. It is, however, at the intermediate latitude zones that the amplitude of the annual component and the irregular variations are large. It is shown that the atmospheric pressure change gives rise to the annual term in the polar motion of the order of 0″.l with its secular variations of 0″.01.