1.  summary:		conservative runoff mapping between r19 and gx3v5

2.  created by:		Steve Yeager
 
3.  date and time:	 August 23, 2004

4.  created on: 	dave
 
5.  dataset format: 	nc
 
6.  endian:		n/a
 
7.  archival copy location:
      /CCSM/csm/inputdata/cpl/cpl6/map_r19_to_gx3v5_20040823.nc
      /CCSM/csm/inputdata/cpl/cpl6/map_r19_to_gx3v5_20040823.readme
 
8.  creation summary:
 
The following is a description of how the netcdf mapping file
between r19 and gx3v5 grids was produced.

First, created a "template" of a r19->gx3v5 SCRIP mapping file
with the following scrip_in:
&remap_inputs
    num_maps = 1
    grid1_file = '/fis/cgd/cseg/csm/mapping/grids/r19.nc'
    grid2_file = '/fis/cgd/cseg/csm/mapping/grids/gx3v5_031205.nc'
    interp_file1 = '/ptmp/yeager/template_r19_to_gx3v5.nc'
    map1_name = 'r19 to gx3v5_031205 Conservative Mapping'
    map_method = 'conservative'
    normalize_opt = 'fracarea'
    output_opt = 'ncar-csm'
    restrict_type = 'latlon'
    num_srch_bins = 10
/

In dave:/cgd/oce/yeager/POP_tools/runoff/, compiled main.F90.dummyr19
(cp main.F90.dummyr19 main.F90; domake.csh) with the following settings:
   runfile   = 'runoff.dat01'   ! 19-basin runoff data file (Large)
   garrfile   = 'garray.ieeer8' ! (nx,ny,nbasin) garray (kg/s/m^2)
   efold = 750000.              ! in meters
   imt = 100
   jmt = 116
   mapf = 'template_r19_to_gx3v5.nc'
   ocngridf = 'horiz_grid_20030806.ieeer8'
   tareaf = 'tarea_gx3v5.ieeer8'
   newmap = 'map_r19_to_gx3v5_20040823.nc'
   newaroff = 'runoff.b19.20040823.nc'

Running the above code produces 3 outputs:
	*) garrfile, a ieeer8 binary which contains the 3D time-independent
	runoff flux field (kg/s/m^2) appropriate for the POP grid.  Dimensions
	are (imt,jmt,basin).  Sums of the POP area-weighted global flux
	will be equal to the basin totals given in runfile.
	*) runoff.b19.20040823.nc & map_r19_to_gx3v5_20040823.nc:
	These files are a pair.  The former, input to dlnd6, is
	19 basin runoff totals (k/s) from runfile normalized by the area of
	1/19 of the globe.  The latter is the cpl6 mapping which, when 
	used with runoff.b19.20040823.nc, will result in the correct 
	flux in (kg/s/m^2) into the ocean (ie, the garrfile field).   

The conservation can be tested using the routine test_r19toOCN_remapping.run.