wgrib2: new_grid_ipopt
Introduction
The new_grid option interpolates from one grid into another.
The new_grid_interpolation option selects the interpolation method.
The new_grid_ipopt option modifies the parameters used by
the interpolation method.
The new_grid_ipopt option MUST FOLLOW
the new_grid_interpolation option because the latter will
overwrite the IPOPT values with the default values for that interpolation method.
 bilinear: ipopt is not used
 bicubic:
 ipopt(1) = 0: straight bicubic
 ipopt(1) = 1: constrained to range of 4 neighboring points
 ipopt(2) = %data converage for output point, default=50%
 nearest neighbor: ipopt is not used
 budget: ipopt is not used
 spectral: (alpha)
 ipopt(1) = 0: triangular truncation
 ipopt(1) = 1: rhomboidal truncation
 ipopt(2) = N: truncation number
 ipopt(2) = 1: sensible truncation number, based on grid
(default for now, will be changed)
note: should specify these values by new_grid_interpolation
when ipopt(2) == 1, sensible trunction number
IROMB = ipopt(1)
IDRT=4 FOR GAUSSIAN GRID
IDRT=0 FOR EQUALLYSPACED GRID INCLUDING POLES
IDRT=256 FOR EQUALLYSPACED GRID EXCLUDING POLES
IF(IROMB.EQ.0.AND.IDRTI.EQ.4) MAXWV=(JMAXI1)
IF(IROMB.EQ.1.AND.IDRTI.EQ.4) MAXWV=(JMAXI1)/2
IF(IROMB.EQ.0.AND.IDRTI.EQ.0) MAXWV=(JMAXI3)/2
IF(IROMB.EQ.1.AND.IDRTI.EQ.0) MAXWV=(JMAXI3)/4
IF(IROMB.EQ.0.AND.IDRTI.EQ.256) MAXWV=(JMAXI1)/2
IF(IROMB.EQ.1.AND.IDRTI.EQ.256) MAXWV=(JMAXI1)/4
Note: The values are appropriate for the spectral GFS Gaussian grid
because the grid values were derived from the spherical harmonics.
The values are not appropriate for the FV3 GFS Gaussian grid
because the grid values were derived by a bilinear interpolation
(mostly) from the cubed sphere grid.
Since NCEP is transitioning to a FV3 model, the grid point values
are not the exact representation of the model fields but rather
a bilinear interpolation from the cubed sphere. So a highwavenumber
noise is being added to the grid values. So the appropriate spectral
representation will have filter applied to the spectral represenation.
The math hasn't been worked out.
 neighborbudget: not enabled by wgrib2
Usage
new_grid_ipopt X
X = integer or integer:integer
See also: new_grid,
new_grid_winds
new_grid_vectors
new_grid usage
if
fi
