1.  summary: 		gx3v5 grid

2.  created by:		Steve Yeager
 
3.  date and time:	August 6, 2003

4.  created on: 	n/a
 
5.  dataset format: 	n/a
 
6.  endian:		n/a
 
7.  archival copy location:
    archival read password: CCSMPOP
 
8.  creation summary:

	The gx3v5 grid was developed in response to complaints that
	low-resolution CCSM coupled solutions (ie, T31-gx3v4) were
	characterized by excessively weak Atlantic meridional 
	overturning in the ocean, making such solutions inadequate
	for paleo work.

	In creating gx3v5, a new set of grid generation tools was employed
	which had not been used for either gx1v3 or gx3v4.  The 'ns_dipole'
	grid code from LANL, modified locally, was used for generating
	a horizontal dipole mesh grid (see /fs/cgd/csm/inputdata/ocn/pop/gx3v5/grid/
	horiz_grid_20030806.readme).  A new vertical grid was also
	created (see /fs/cgd/csm/inputdata/ocn/pop/gx3v5/grid/
	topography_20030806.readme), and a new kmt editing tool was used
	to excavate model topography by hand in key locations.   

	While the new gx3v5 has the same resolution as the old gx3v4 (100x116x25),
	there are many important differences which are summarized below:
	
	* new horizontal grid (generated with 'ns_dipole') has a north pole location
	  slightly further south, and the distribution of grid points is different,
	  with more resolution focused near the poles and away from midlatitudes 
	  (compare /fs/cgd/data0/yeager/POP_GRIDS/gx3v5.012/grid.ps with
	  /fs/cgd/data0/yeager/POP_GRIDS/gx3v4/grid.ps).  Wasted grid points over
	  land near the poles have been minimized.  The new grid mesh generator
	  maintains near unity aspect ratio over more of the globe than in gx3v4.

	* new vertical grid (generated with /home/dataproc/yeager/CCSM/lowres/pop_depths.f)
	  has smaller DZ in the top 200m than was used with the old gx3v4 (view comparison
	  at http://www.cgd.ucar.edu/oce/yeager/ccsm_data/gx3v5.010/L25.gif).  Consequently,
	  the new vertical grid for gx3v5 has larger DZ in the deep ocean, with max DZ =
	  500m.

	* The new gx3v5 kmt array (computed from horizontal grid, vertical grid, & etopo5
	  data) has been hand edited so that now the Canadian archipelago has been
	  opened up (made possible because of enhanced northern resolution).  Other 
	  inherent differences & edits mean that the gx3v5 kmt is substantially different
	  from the gx3v4 kmt.

 
9.  derived from:
 
10. code, scripts, namelists, etc, used to create this file:

	See all code and scripts in the gx3v5 directory
	/fs/cgd/data0/yeager/POP_GRIDS/gx3v5.012/

	(named for the case gx3v5.012 which represented the definitive
	 test case for gx3v5).

	See low-res CCSM page http://www.cgd.ucar.edu/oce/yeager/gx3v5.html
	for comparisons which led to this gx3v5 version.