HR: 0800h
AN: G41C-0366    [Abstracts]
TI: Time-varying Annual Signals in Geodetic Observation and in Atmospheric and Oceanic Excitations during 1980-2001
AU: * Masaki, Y
EM: ymasaki@gsi.go.jp
AF: Geographical Survey Institute, 1, Kitasato, Tsukuba, Ibaraki, 305-0811 Japan
AB: The polar motion is composed of two modes: The annual wobble and the Chandler wobble. The Chandler wobble, containing information on the Earth interior, is extracted from the observed polar motion by removing seasonal signals. However, since the seasonal variations are excited by geophysical fluids (e.g. the atmosphere, the oceans, the land water), the seasonal signals show different patterns year by year. In this study, we examined the time-variations of the annual signals in the observed polar motion and in the atmospheric and oceanic excitations (i.e. AAM and OAM functions) over 22 years. We extracted 7-yr data from these time-series in order to estimate the seasonal variations. We calculate the AAM functions from three meteorological reanalysis data sets available today, with IB hypothesis. The OAM values used in this study are downloaded from the website of the IERS Global Geophysical Fluids Center, Special Bureau for the Oceans. We found that the time-variations of the annual AAM+OAM signals have similar patterns to that of the observed annual signals. That means, on the other hand, the annual terms do not show constant amplitude/phase during the period. We will discuss its effects on the retrieved Chandler signals.
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1239 Earth rotation variations
SC: Geodesy [G]
MN: Fall Meeting 2005