1.  summary: 		19-Basin Runoff Totals
			for gx3v5 grid.

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

4.  created on: 	dave
 
5.  dataset format: 	netcdf
 
6.  endian:		N/A
 
7.  archival copy location:
       /CCSM/csm/inputdata/lnd/dlnd6/runoff.b19.20040823.nc
       /CCSM/csm/inputdata/lnd/dlnd6/runoff.b19.20040823.readme
 
8.  creation summary:
	
	runoff.b19.20040823.nc is the "data.runoff.nc" file
	described below, for gx3v5 grid settings.

	The information below can be found in 
	/fis/cgd/oce/yeager/POP_tools/runoff/runoff_smooth_mod.F90

	(see also map_r19_to_gx3v5_20040823.readme)

!-------------------------------------------------------------------------------
! o Based on M. Hecht's /fs/cgd/home0/hecht/csm/runoff/transfer_matrix.ncl
! o Compute correct weights to map 19-element 'normalized' runoff flux vector
!   (kg/s/m^2) onto the POP ocean grid.
!
!       R(j)  = net runoff (kg/s) into basin j
!       dA(j) = fictitious area (m^2) associated with basin j (1/19 of globe)
!               from scrip
!       F(j)  = "flux" sent to cpl by dlnd = R(j)/dA(j) (kg/s/m^2)
!               (This flux is stored in the data_aroff netcdf file)
!       garr(i)  = flux which should go into ocean cell i, as determined by
!                routine dummyflux (sum over i is known to preserve R when
!                multiplied by ocean areas!)
!       dA_o(i) = area (m^2) associated with ocean cell i, from POP
!       dA_s(i) = area (m^2) associated with ocean cell i, from scrip
!
!   Then in order to preserve R(i), the mapping weights should be
!       s(i,j) = dA(j)*[garr(i)/R(j)]*[dA_o(i)/dA_s(i)]
!
!   The "flux" mapping, then will be:
!       Fo(i) = sum_over_j{s(i,j)*F(j)}
!             = sum_over_j{dA(j)   garr(i)    dA_o(i)   R(j)  }
!                         {     * --------- * ------- * ----  }
!                         {        R(j)       dA_s(i)   dA(j) }
!             = garr(i) * dA_o(i)/dA_s(i)
!
!   Before sending to the ocean, the couple will multiply Fo(i) by
!   an area correction factor, so that
!       F*o(i) = runoff flux received by ocean model (kg/s/m^2)
!              = Fo(i) * dA_s(i)/dA_o(i)
!              = garr(i), by definition the correct flux into ocean cell i
!
!   Therefore, sum_over_i{F*o(i)*dAo(i)} = sum_over_j{R(j)}
!
!-------------------------------------------------------------------------------

!-------------------------------------------------------------------------------
! o Once garr has been defined after a call to dummyflux, this routine
!   will output a data.runoff.nc file for 19-basin data runoff.  This
!   file is needed by dlnd6, and both "domain.runoff.nc" and "data.runoff.nc"
!   get softlinked to this file in the dlnd buildnml script.  The dlnd
!   namelist parameter data_aroff will get set to this file.
!
! o The contents of the netcdf are fictitious 19-basin grid information (derived
!   from the r19.nc file through the sMatrix "map") and runoff values for each
!   basin in kg/s/m^2.  These values are computed as the total runoff for each
!   basin as specified in srcfile (kg/s) normalized by a fictitious area
!   (1/19 of the globe) in m^2.
!-------------------------------------------------------------------------------
 
9.  derived from:
	see # 8
 
10. code, scripts, namelists, etc, used to create this file:
	/fis/cgd/oce/yeager/POP_tools/runoff/main.F90.dummyr19
	with settings:
	   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'