44. Horizontal friction discretization

The purpose of this appendix is to present a derivation of MOM's discretized horizontal friction operator. Much here follows the functional approach used for the isoneutral diffusion discretization in Appendix C. However, the present discussion is considerably simpler because of the need to only discretize a two dimensional (x-y plane) operator, and because there are no subtleties associated with neutral directions. The approach here is therefore a straightforward application of the functional formalism outlined in Section 9.7 for the continuum friction, and Appendix C for the diffusion operator.

Brief history of this method in MOM:

• Summer 1999: Discretization derived and tested on one-processor and only for fully opened memory window. This scheme will not be made available for use in MOM 3 as it is motivated largely by the desire to introduce generalized horizontal coordinates, which is being considered for MOM 4 but not MOM 3.