Global mean sea surface and marine gravity anomaly from multi-satellite
altimetry: applications of deflection-geoid and inverse Vening Meinesz formulae
Cheinway Hwang, Dept. of Civil Engineering, National Chiao Tung University, 1001 Ta Hsueh
Road, Hsinchu 300, Taiwan. hwang@geodesy.cv.nctu.edu.tw. Phone: +886-3-5724739. Fax:
+886-3-5716257
Hsin-Ying Hsu, Dept. of Civil Engineering, National Chiao Tung University, 1001 Ta Hsueh Road,
Hsinchu 300, Taiwan. patri@geodesy.cv.nctu.edu.tw. Phone: +886-3-5712121ext54990. Fax:
+886-3-5716257.
Rung-Jie Jang, Dept. of Civil Engineering, National Chiao Tung University, 1001 Ta Hsueh Road,
Hsinchu 300, Taiwan. bryan@geodesy.cv.nctu.edu.tw Phone: +886-3-5724739. Fax:
+886-3-5716257
Global mean sea surface heights (SSHs) and gravity anomalies on a 2´×2´ grid were determined
from Seasat, Geosat (ERM and GM), ERS-1 (1.5-year mean of 35-day, and GM),
TOPEX/POSEIDON (T/P) (5.6-year mean) and ERS-2 (2-year mean) altimeter data over the region
0°-360° longitude and –80°-80° latitude. To reduce ocean variabilities and data noises, SSHs from
non-repeat missions were filtered by Gaussian filters of various wavelengths. A Levitus oceanic
dynamic topography was subtracted from the altimeter-derived SSHs, and the resulting heights were
used to compute along-track deflection of the vertical (DOV). Geoidal heights and gravity anomalies
were then computed from DOV using the deflection-geoid and inverse Vening Meinesz formulae.
The Levitus oceanic dynamic topography was added back to the geoidal heights to obtain a
preliminary sea surface grid. The difference between the T/P mean sea surface and the preliminary
sea surface was computed on a grid by a minimum curvature method and then was added to the
preliminary grid. The comparison of the NCTU01 mean sea surface height (MSSH) with the T/P and
the ERS-1 MSSH result in overall RMS differences of 5.0 and 3.1 cm in SSH, respectively, and 7.1
and 3.2 μrad in SSH gradient, respectively. The RMS differences between the predicted and
shipborne gravity anomalies range from 3.0 to 13.4 mgals in 12 areas of the world oceans.
Oral presentation
Geodesy