ESTIMATION OF DYNAMIC OCEAN TOPOGRAPHY IN THE GULF-STREAM AREA USING THE HOTINE FORMULA AND ALTIMETRY DATA

Two modifications of the Hotine formula using the truncation theory an d marine gravity disturbances with altimetry data are developed and us ed to compute a marine gravimetric geoid in the Gulf Stream area. The purpose of the geoid computation from marine gravity information is to derive the absolute dynamic ocean topography based on the best estima te of the mean surface height from recent altimetry missions such as G eosat, ERS-1, and Topex. This paper also tries to overcome difficultie s of using Fast Fourier Transformation (FFT) techniques to the geoid c omputation when the Hotine kernel is modified according to the truncat ion theory. The derived absolute dynamic ocean topography is compared with that from global circulation models such as POCM4B and POP96. The RMS difference between altimetry-derived and global circulation model dynamic ocean topography is at the level of 25 cm. The corresponding mean difference for POCM4B and POP96 is only a few centimeters. This s tudy also shows that the POP96 model is in slightly better agreement w ith the results derived from the Hotine formula and altimetry data tha n POCM4B in the Gulf Stream area. In addition, Hotine formula with mod ification (II) gives the better agreement with the results from the tw o global circulation models than the other techniques discussed in thi s paper.