Relax

Domain-independent source code for interpolation of a climatology to a HYCOM model grid for use in boundary relaxation zones or for model initialization.

HYCOM-tools/relax/src

All programs read regional.grid.b at run-time to get idm and jdm for the particular region being processed. They may also read regional.grid.a to find the grid location.

The Makefile is configured to key on ../../config/$(ARCH)_setup for machine-dependent definitions, see the Config Setup wiki page. When running on (say) a Linux PC, ARCH is "intel*" and an individual make command for gfortran might be:
make rmu ARCH=intelGF >& Make_rmu.log

Typically all executables are created just once by editing Make_all.src for the correct ARCH and then issuing the command csh Make_all.csh.

The climatology data sets are input on their native grid. The HYCOM-tools/bin/clim_stat command lists the contents of the *.d native climatology file (Levitus climatology). All fields must be defined at all grid points (including over land and below the ocean floor), and the potential density vertical profile must be stable at all locations.

The climatology is first interpolated to the HYCOM grid at its native fixed z-levels, e.g., by z_levitus.f, z_woa13.f, etc. The result is then converted to the "isopycnal" climatology required for a particular HYCOM simulation via relaxi.f. Splitting the process into two phases saves time, because the z-level climatology does not depend upon the isopycnals chosen by a particular HYCOM simulation. Also relaxi.f does not depend on which climatology is being used (providing all the native climatologies use the same number of z-levels in the vertical).

The output data sets are climatological interface depth, and potential temperature and salinity fields, for the specified set of isopycnal layers and the specified set of minimum near-surface thicknesses.

These programs handle a single set of climatology fields. Since HYCOM expects six bi-monthly or twelve monthly sets of fields in a single file, the individual output climatology files must be concatenated before use.

The HYCOM climatology can be used for initializing the model (iniflg=2), for surface relaxation to augment surface atmospheric forcing (trelax=1 and/or srelax=1), and for lateral boundary nudging (relax=1). In the latter case, a relaxation mask is required to specify where and how much relaxation to apply. It can be generated by rmu_linear.f.