OTIS - OSU Tidal Inversion Software
Gary D. Egbert and Lana Erofeeva
OTIS is a package of programs for tidal data assimilation based on methods used by Egbert, Bennet, Foreman in [EBF] for the global inverse solution TPXO ( TPXO.7.1) is current version of the global solution). Major changes to the software have been made to significantly improve computational efficiency and ease of use for regional tidal modeling constrained by altimetry data (other kinds of data, such as tide gauges, current meters, CODAR, ship mounted ADCP data are also allowed). As in EBF, a modified or reduced basis representer approach is used. That is, representers are calculated for a subset of data locations, and a solution to the variational problem is sought within the space of linear combinations of calculated representers. With this approach it is quite feasible to fit all available altimetry data in a modest sized area (e.g., 20 degrees by 20 degrees, with data at several thousand locations) using a few hundred representers per constituent. In this version representers are calculated by solving the linearized frequency domain shallow water equations (SWE) after factoring the matrix of coefficients for the elevation wave equation (on details see Efficient inverse modeling of barotropic ocean tides , Journal of Atmospheric and Oceanic Technology, vol.19,N2, February 2002). This approach allows for a decrease in computational time (relative to the time stepping approach used for the representer calculation of EBF) by a factor of 100 or more. Combined with the reduced basis approach this allows solution of moderate size problems on a high-end workstation with 500Mb of RAM. OTIS has been developed and tested on a single processor IBM RS6000, and then adapted for several other computer platforms, including DEC Alpha and Sun Ultra 10. It is written in FORTRAN-90, FORTRAN-77 and MATLAB to be compiled and run under UNIX.
See OTIS documentation for details on the package.
OTIS has been applied to get tidal solutions for various local areas. Regional solutions for these areas are available.
OTIS software is available through anonymous ftp coas.oregonstate.edu in dist/tides/OTIS.