tidal_forcing module reference¶
Code by Robert Hallberg, August 2005, based on C-code by Harper Simmons, February, 2003, in turn based on code by Brian Arbic.
Detailed Description¶
The main subroutine in this file calculates the total tidal contribution to the geopotential, including self-attraction and loading terms and the astronomical contributions. All options are selected with entries in a file that is parsed at run-time. Overall tides are enabled with the run-time parameter ‘TIDES=True’. Tidal constituents must be individually enabled with lines like ‘TIDE_M2=True’. This file has default values of amplitude, frequency, Love number, and phase at time 0 for the Earth’s M2, S2, N2, K2, K1, O1, P1, Q1, MF, and MM tidal constituents, but the frequency, amplitude and phase ant time 0 for each constituent can be changed at run time by setting variables like TIDE_M2_FREQ, TIDE_M2_AMP and TIDE_M2_PHASE_T0 (for M2).
In addition, the approach to calculating self-attraction and loading is set at run time. The default is to use the scalar approximation, with a coefficient TIDE_SAL_SCALAR_VALUE that must be set in the run-time file (for global runs, 0.094 is typical). Alternately, TIDAL_SAL_FROM_FILE can be set to read the SAL from a file containing the results of a previous simulation. To iterate the SAL to convergence, USE_PREVIOUS_TIDES may be useful (for details, see Arbic et al., 2004, DSR II). With TIDAL_SAL_FROM_FILE or USE_PREVIOUS_TIDES,a list of input files must be provided to describe each constituent’s properties from a previous solution.
This module also contains a method to calculate self-attraction and loading using spherical harmonic transforms. The algorithm is based on SAL calculation in Model for Prediction Across Scales (MPAS)-Ocean developed by Los Alamos National Laboratory and University of Michigan (Barton et al. (2022) and Brus et al. (2022)).
Barton, K.N., Nairita, P., Brus, S.R., Petersen, M.R., Arbic, B.K., Engwirda, D., Roberts, A.F., Westerink, J., Wirasaet, D., and Schindelegger, M., 2022: Performance of Model for Prediction Across Scales (MPAS) Ocean as a Global Barotropic Tide Model. Journal of Advances in Modeling Earth Systems, in review.
Brus, S.R., Barton, K.N., Nairita, P., Roberts, A.F., Engwirda, D., Petersen, M.R., Arbic, B.K., Wirasaet, D., Westerink, J., and Schindelegger, M., 2022: Scalable self attraction and loading calculations for unstructured ocean models. Ocean Modelling, in review.