The Python 3 script tidal_potential.py calculates the tidal forcing for a given year and saves it in hourly increments. The script calculates the potential from knowledge of the position of the sun and moon at a given moment, and it corrects for the solid-earth tide. See, for example, Wunsch: Modern Observational Physical Oceanography, 2015, chapter 6 for the relevant theory.

This script makes use of the NASA software SPICE. The script requires the package spiceypy, which is a Python wrapper to SPICE. The script also requires the kernels listed in meta_kernel, which can be downloaded from NASA's Navigation and Ancillary Information Facility.

To generate the tidal forcing for the year 2018, execute the script with:

./tidal-potential.py 2018 IAU_EARTH

or

python3 tidal-potential.py 2018 IAU_EARTH

The forcing fields that can be read into the ocean model are written to input/.

SPICE uses Earth orientation data provided by a PCK kernel. The IAU_EARTH orientation model has relatively low accuracy but extends into the future indefinitely. Should higher accuracy be needed, use ITRF93 instead. To use this, be sure to add either earth_070425_370426_predict.bpc or earth_latest_high_prec.bpc to meta_kernel, depending on whether you need prediction or not. See the documentation of the IAU_EARTH kernel for a discussion of its accuracy and the documentation of the high-accuracy kernels for which one to use.