Tools for Displaced-PoleOcean Grid Generation for CCSM2

Steve Yeager Rick SmithEsther Brady John Davis

What needs to be modified?1. OCN

horiz_grid : ieee r8, {ulat,ulng,htn,hte,hus,huw,utan}topography : ieee i4, {kmt}region_mask : ieee i4 {regionmask}other input_template files…

2. CPLmap_ATM_to_OCN_aave.ncmap_ATM_to_OCN_bilin.ncmap_OCN_to_ATM_aave.ncmap_RUNOFF_to_OCN.nc

Tools

ns_dipole.F generates a dipole mesh grid, (R Smith et al)

topography.F Generates a kmt based on etopo5 data, (R Smith et al)

paleotopo.F90 Generates a kmt based on paleo data

display_hgrid_land.F Grid display with land mask, (R Smith et al)

eCubed (C++ package) Interactive grid display & kmt edit, (J Davis et al)

grid_bin2nc.F90 Creates a netcdf file of grid info

gridkmt_nc2bin.F90 Writes kmt in netcdf back into binary

ncview (C++ package) All-purpose netcdf viewer (D Pierce) (http://meteora.ucsd.edu/~pierce/ncview_home_page.html)

SCRIP (F90 package) Remapping between grids (P Jones) (http://climate.acl.lanl.gov/software/SCRIP/scrip_frames.htm) (http://www.cgd.ucar.edu/csm/models/ocn-pop/scrip.shtml)

mk_grid.csh Automates grid generation procedure, including grid & kmt

mk_ocninput.csh Automates ocn input file modification, including region mask

mk_remap.csh Automates atmosphereocean map generation

mk_runoff_remap.csh Automates runoffocean map generation

map_runoff (F90 package) Correction routines for runoffocean map

1. a. Generating a Grid

• ns_dipole* generates a dipole mesh grid with user-specified north/south pole locations.

• Equator is always a grid line• Enhanced meridional

resolution at the equator• Code tries to make aspect

ratio 1 • Nx is independent variable

(sets the order of the resolution); Ny requires iteration

Created using display_hgrid* (R Smith et al)

1. b. Generating a kmt • topography* assigns topography/kmt

to a grid based on the 1/12 degree etopo5 dataset.

Created using display_hgrid_land*

• paleotopo* assigns topography/kmt to a grid based on a paleo bathymetry dataset in netcdf format.

Iterate grid/kmt generation until

… for a given Nx and equatorial gaussian function, Ny is sufficient to extend the grid into the polar continents without wasting resolution,

… grid has acceptable min/max cell sides & aspect ratios for active ocean points (when compared to standard grids)

1. c. Hand Edit Kmt

• eCubed* enables interactive grid-viewing/kmt-editing using a mouse & keyboard

• Reads/writes a grid netcdf file created with grid_bin2nc*

• Convert kmt back into POP input binary with gridkmt_nc2bin*

Created using display_hgrid_land*Created using eCubed*

2. a. Maps between ATM & OCN

• mk_remap.csh creates atmosphereocean mappings using SCRIP (Spherical Coordinate Remapping and Interpolation Package) developed by Phil Jones.

2. b. Mapping Runoff to OCN

• mk_runoff_remap.csh calls SCRIP; generates a conservative runoffocean mapping netcdf.

• BUT, it does not guarantee global water conservation• ALSO, it may require additional smoothing to prevent

excessively low ocean salinities in high runoff regions.

• Use map_runoff/*.F90 for – runoff map conservation correction– map matrix testing– ocean smoothing map generation & testing– map matrix multiplication.

Why are conservation corrections needed?

Potential flux loss

…where an active source grid cell does not overlap any (a) or only partially overlaps (b) a destination cell.

…where an active source grid cell maps into an inactive destination cell (c)

runoff_conserve_mod.F90 applies corrections

Runoff Smoothing

• runoff_smooth_mod.F90 contains routines for generating an ocean-to-ocean smoothing map

• Input parameters maxradius (km) & efold (km)

• test_smooth generates netcdf output of smoothing effects for select source points

efold = 100km, maxradius = 500km

Runoff-to-Ocean Map with Smoothing

• runoff_map_mod.F90 contains routines for matrix multiplication & testing:

=

runoff grid ocean grid runoff grid

Final Map Smoothing Map Corrected SCRIP Map

o ce a

n g r

id

o ce a

n g r

id

o ce a

n g r

id

efold = 100km, maxradius = 500km

efold = 2000km, maxradius = 500km

Surface Salinity Effect of Smoothing Runoff