GDVINT performs interpolation between vertical coordinates.
INPUT PARAMETERS
GDFILE *Grid file
GDOUTF *Output grid file
GDATTIM *Grid date/time
GVCORD *Grid vertical coordinate
GLEVEL *Grid level
MAXGRD *Maximum number of grids
GAREA *Graphics area
VCOORD *Vertical coordinate type
PROGRAM DESCRIPTION
This program performs vertical interpolations from one
input vertical coordinates to another. The output grid
file may be the same as the input file or be a separate
file. If areal subsetting is specified, output must be
to another GEMPAK file.
The input file is specified in GDFILE and the output file
in GDOUTF. If GDOUTF does not exist, then a new file
will be created with the maximum number of grids given
in MAXGRD. GDATTIM specifies the time at which to
perform the interpolation.
GVCORD specifies the input and output vertical
coordinates separated by a slash. The coordinates
supported are:
PRES -- pressure
THTA -- potential temperature
HGHT -- height above sea level
SGMA -- sigma p
ETA -- eta (coordinate is not supported by GEMPAK)
ZAGL -- height above ground level
When SGMA or ETA is specified, the pressure on SGMA or
ETA =0 is given following a semicolon. For example, if
the pressure at SGMA=0 is 50 mb, the specification in
GVCORD is
SGMA:50
GLEVEL specifies the vertical coordinate levels to
interpolate. This may be a single level, a list of
levels separated by semicolons or a range with an
increment separated by dashes (see examples below).
GAREA specifies areal subsetting. It can be specified
as either lower-left and upper-right grid
coordinates, separated by semicolons and preceded by
a single @, or as lower-left and upper-right latitude
and longitude coordinates separated by semicolons.
In the latter case, the locations are rounded to the
nearest grid points. The navigation projection and its
parameters are used along with the specified corner
points to set the navigation in the output grid file.
If areal subsetting is used, the output file must be
different from the input file.
VCOORD specifies a list of GEMPAK coordinate names.
All grids at the specified time having one of these
coordinate names will be transfered to the output
file with no interpolation performed. This allows
surface grids with vertical coordinate types NONE
or ESFC to be transfered into the output file. It
also allows subsetting of grids in other vertical
coordinates to be put into the output file. VCOORD
is also used to specify the Lorenz condition for
interpolation into THTA coordinate. To specify
the Lorenz condition, conclude the VCOORD input
with /L.
If the output vertical coordinate is THTA and
the Lorenz condition is specified, underground
isentropic surfaces are assigned surface values,
and PSYM is built down hydrostatically using the
surface pressure in the Exner function. In all
other cases, underground surfaces are assigned
missing values.
If surface values of the interpolated parameters
are not available, GDVINT extrapolates values to the
surface from two levels above the surface. These
values are used in the interpolation and are placed
in the output file where they are assigned the
output vertical coordinate and GLEVEL=0.
If heights are not available in the input grid file,
a hydrostatic integration is done in the input coordinate
to generate values for the interpolation.
EXAMPLES
1. Interpolate from pressure to theta levels from
256K to 412K with an interval of 4K for the entire
grid. Write the output to a new file. Also
transfer grids with vertical coordinates of NONE
from the input to the output file. Don not apply
the Lorenz condition for underground surfaces.
Thus, underground surfaces will be assigned missing
values.
GDFILE = z00jun16.ngmpres
GDOUTF = z00jun16.ngmthta
GDATTIM = f24
GLEVEL = 256-412-4
GVCORD = pres/thta
MAXGRD = 2000
GAREA =
VCOORD = none
2. Interpolate from sigma, with P(SGMA=0) = 0 to
theta over a subgrid defined by the latitude
and longitude bounds. The actual subgrid will
be defined by the grid points closest to the
latitude longitude bounds. Also transfer all
grids with vertical coordinates NONE, MSLV and
ESFC into the output file. Apply the Lorenz
condition for underground surfaces.
GDFILE = z00jun16.ngmsgm
GDOUTF = z00jun16.ngmtht
GDATTIM = f24
GLEVEL = 256-412-4
GVCORD = sgma:0/thta
MAXGRD = 2000
GAREA = 30;-100;45;-70
VCOORD = none;mslv;esfc/L
3. Interpolate from pressure to the height above
ground coordinate over a subset of the grid
specified by grid index bounds. The data is
only interpolated to the 10,000 ft AGL level.
GDFILE = z00jun16.ngmprs
GDOUTF = z00jun16.ngmzag
GDATTIM = f36
GLEVEL = 10000
GVCORD = pres/zagl
MAXGRD = 3200
GAREA = @12;23;34;78
VCOORD = mslv;esfc
4. Interpolate from isentropic coordinates to sigma
(ptop=50) over the entire grid. The data is
interpolated to the 0.1, 0.3, and 0.6 sigma levels,
since the values are scaled by 10000. Put the
output in the same file as the input. In this example,
maxgrd is ignored.
GDFILE = z00jun16.ngm
GDOUTF = z00jun16.ngm
GDATTIM = f48
GLEVEL = 1000;3000;6000
GVCORD = thta/sgma:50
MAXGRD = 3200
GAREA = grid
VCOORD = none;esfc
ERROR MESSAGES
[gdvint +3] No pressure on this level.
[gdvint +2] No output vertical coordinate value on this level.
[gdvint +1] All values are missing.
[gdvint -1] Fatal error initializing TAE.
[gdvint -2] Fatal error reading TAE parameters.
[gdvint -3] Fatal error initializing GEMPLT.
[gdvint -4] No thermodynamic data in the input file.
[gdvint -5] Navigation blocks are different.
[gdvint -6] Required surface pressure is absent.
[gdvint -7] Required surface elevation is absent.
[gdvint -8] Too few levels to interpolate this parameter.
[gdvint -9] No parameters to interpolate -- check GVCORD, GDATTIM.
[gdvint -10] Top pressure for SGMA or ETA missing.
[gdvint -11] Subset region is invalid.
[gdvint -12] File ... cannot be opened.
[gdvint -13] User specified coordinates are invalid.
[gdvint -14] Levels not correctly specified.