Redetermination of the precise gravity fields around the Japanese Antarctic Station, Syowa, and evaluation of GOCE EGMs
Abstract:We have been conducting the precise gravity field determination around the Japanese Antarctic Station, Syowa in Lützow-Holm Bay, East Antarctica. So far, we employed GOCE (Gravity field and steady-state Ocean Circulation Explorer) RL-4 and earlier versions of the EGMs and the in-situ gravity data obtained by the Japanese Antarctic Research Expedition (JARE), i.e., land gravity data since 1967, surface ship data since 1985 and airborne gravity data in 2006. Using these data sets, we calculated the precise gravity fields by means of Least Squares Colocations (LSC) and evaluated the GOCE EGMs by comparing with the in-situ gravity data.
Recently, new GOCE EGMs, TIM RL-5 and DIR RL-5 have been released. In addition, JARE ship borne gravity data have been reprocessed following a more unified procedure and some land gravity data have been added. Accordingly, we have recalculated the gravity fields using all the data combined. Practically, using those data sets, we estimated gravity anomalies and geoid heights in the area of 60-80S and 20-60E by means of LSC using a GOCE EGM as the long wave-length gravity fields and an empirical covariance function estimated from the airborne gravity data. In this procedure as well as using the obtained gravity field data, we also evaluated GOCE EGMs and other recent EGMs.