Record Details
An Inversion Method to Determine Ocean Surface Currents Using Irregularly Sampled Satellite Altimetry Data
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | An Inversion Method to Determine Ocean Surface Currents Using Irregularly Sampled Satellite Altimetry Data |
| Names |
Mesias, Jorge M.
(creator) Strub, P. Ted (creator) |
| Date Issued | 1995-08 (iso8601) |
| Abstract | An inversion method is presented that determines mesoscale sea surface currents using satellite altimeter data. The method directly uses geostrophic cross-track velocity components, expands the unknown velocity components with spline functions, and includes weighted constraints for divergence and kinetic energy. The success of this method is measured by the misfit between input and output velocities and depends on the weights of the constraints, the irregular space-time data distribution of the altimeter data, and the nonstationary character of mesoscale oceanic features. Negative effects of the irregular spatial distribution of the altimeter data are overcome by partitioning the larger regions of interest into smaller subareas to make independent inversions. The relatively weak effects of subtrack temporal separations in the presence of slowing evolving fields are addressed by temporal interpolations, which provide the more important benefit of filling in missing data. The procedure is evaluated for the Geosat, Topex-Poseidon, and ERS-1 altimeter sampling geometries determining their “oceanic” resolutions by using simulated stationary and nonstationary velocity fields. As expected for stationary fields the best spatial resolutions correspond to altimeters with the densest data distributions, that is, the longest repeat periods. The smallest scale resolved is approximately 100 km for Geosat (17-day repeat) and ERS-1 (35-day repeat) and is approximately 150 km for Topex-Poseidon (10-day repeat). Tests with simulated nonstationary “eddies” show that the propagation at typical Rossby wave phase speeds (<0.04 m s⁻¹) degrades the solutions only slightly if scales are greater than approximately 200 km for Topex-Poseidon and 150 km for Geosat and ERS-1 17-day periods, even without temporal interpolation. Combination of Topex-Poseidon and ERS-1 data over 17 days provides the best resolution, allowing eddy spatial scales of 100 km to be resolved at the same propagation speeds. Applications of the inverse method to data from the Geosat and Topex-Poseidon missions indicate that application of the method results in spatial resolution similar to the synthetic experiments. Qualitative comparisons to acoustic Doppler current profilers, satellite surface temperature, and dynamic height fields show that application of the method to Geosat data resolves the larger mesoscale structures of a meandering jet in the California Current. Use of temporal interpolation provides little benefit, due to the slow propagation times of the 100–200-km scale features resolved by the method, but it does help fill in missing data for Geosat. Application of the method to Topex-Poseidon data is not as successful but still resolves the largest-scale structure. The results of application to the synthetic data suggest that it is possible to achieve greater resolution by combining two or more satellite altimeter datasets such as Topex-Poseidon and ERS-1. |
| Genre | Article |
| Identifier | Mesias, Jorge M., P. Ted Strub, 1995: An Inversion Method to Determine Ocean Surface Currents Using Irregularly Sampled Satellite Altimetry Data. Journal of Atmospheric and Oceanic Technology, 12, 830–849. |
