Rotated equidistant cylindrical GRIB decoder and grid coordinate transformations for Arakawa grid E. More...

Data Types
type	ip_rot_equid_cylind_egrid

Functions/Subroutines
subroutine	gdswzd_rot_equid_cylind_egrid (self, IOPT, NPTS, FILL, XPTS, YPTS, RLON, RLAT, NRET, CROT, SROT, XLON, XLAT, YLON, YLAT, AREA)
	Calculates Earth coordinates (iopt = 1) or grid coorindates (iopt = -1) for rotated equidistant cylindrical grids. More...

subroutine	init_grib1 (self, g1_desc)
	Initializes a rotated equidistant cylindrical grid given a grib1_descriptor object. More...

subroutine	init_grib2 (self, g2_desc)
	Initializes a rotated equidistant cylindrical grid given a grib2_descriptor object. More...

subroutine	rot_equid_cylind_egrid_error (IOPT, FILL, RLAT, RLON, XPTS, YPTS, NPTS)
	Error handler. More...

subroutine	rot_equid_cylind_egrid_grid_area (FILL, AREA)
	Computes the grid box area for a rotated equidistant cylindrical grid. More...

subroutine	rot_equid_cylind_egrid_map_jacob (FILL, RLON, XLON, XLAT, YLON, YLAT)
	Computes the map jacobians for a rotated equidistant cylindrical grid. More...

subroutine	rot_equid_cylind_egrid_vect_rot (RLON, CROT, SROT)
	Computes the vector rotation sines and cosines for a rotated equidistant cylindrical grid. More...

Variables
real(kind=kd)	clat
	Cosine of the latitude. More...

real(kind=kd)	clat0
	Local copy of clat0. More...

real(kind=kd)	clatr
	Cosine of the rotated latitude. More...

real(kind=kd)	clon
	Cosine of the difference between rlon and rlon0. More...

real(kind=kd)	dlats
	Local copy of dlats. More...

real(kind=kd)	dlons
	Local copy of dlons. More...

integer	irot
	Local copy of irot. More...

integer, parameter	kd = real64
	Kind of reals. More...

real(kind=kd)	rerth
	Radius of the Earth. More...

real(kind=kd)	rlon0
	Local copy of rlon0. More...

real(kind=kd)	slat
	Sine of the latitude. More...

real(kind=kd)	slat0
	Local copy of slat0. More...

real(kind=kd)	slatr
	Sine of the rotated latitude. More...

Detailed Description

Rotated equidistant cylindrical GRIB decoder and grid coordinate transformations for Arakawa grid E.

(To handle the A through D grids, see ip_rot_equid_cylind_grid_mod).

The E stagger is a bit odd because the 'wind' points shift by half a grid box in each row. That makes the logic tricky. So the routine does its computations by rotating the grid by 45 degrees.

See more info about Awakawa grids.

Octet numbers refer to GRIB2 - GRID DEFINITION TEMPLATE 3.1 Rotate Latitude/Longitude.

Author: George Gayno, Mark Iredell, Kyle Gerheiser

Date: July 2021

Function/Subroutine Documentation

◆ gdswzd_rot_equid_cylind_egrid()

subroutine ip_rot_equid_cylind_egrid_mod::gdswzd_rot_equid_cylind_egrid	(	class(ip_rot_equid_cylind_egrid), intent(in)	self,
		integer, intent(in)	IOPT,
		integer, intent(in)	NPTS,
		real, intent(in)	FILL,
		real, dimension(npts), intent(inout)	XPTS,
		real, dimension(npts), intent(inout)	YPTS,
		real, dimension(npts), intent(inout)	RLON,
		real, dimension(npts), intent(inout)	RLAT,
		integer, intent(out)	NRET,
		real, dimension(npts), intent(out), optional	CROT,
		real, dimension(npts), intent(out), optional	SROT,
		real, dimension(npts), intent(out), optional	XLON,
		real, dimension(npts), intent(out), optional	XLAT,
		real, dimension(npts), intent(out), optional	YLON,
		real, dimension(npts), intent(out), optional	YLAT,
		real, dimension(npts), intent(out), optional	AREA
	)

private

Calculates Earth coordinates (iopt = 1) or grid coorindates (iopt = -1) for rotated equidistant cylindrical grids.

Works for e-staggered rotated equidistant cylindrical projections. The scan mode determines whether this is an "h" or "v" grid.

If the selected coordinates are more than one gridpoint beyond the the edges of the grid domain, then the relevant output elements are set to fill values.

The actual number of valid points computed is returned too. Optionally, the vector rotations, the map jacobians and the grid box areas may be returned as well.

To compute the vector rotations, the optional arguments 'srot' and 'crot' must be present.

To compute the map jacobians, the optional arguments 'xlon', 'xlat', 'ylon', 'ylat' must be present.

To compute the grid box areas, the optional argument 'area' must be present.

Parameters

[in]	self	The grid object gdswzd was called on.
[in]	iopt	option flag +1 to compute earth coords of selected grid coords. -1 o compute grid coords of selected earth coords.
[in]	npts	Maximum number of coordinates.
[in]	fill	Fill value to set invalid output data. Must be impossible value; suggested value: -9999.
[in,out]	xpts	Grid x point coordinates if iopt>0.
[in,out]	ypts	Grid y point coordinates if iopt>0.
[in,out]	rlon	Earth longitudes in degrees e if iopt<0 (Acceptable range: -360. to 360.)
[in,out]	rlat	Earth latitudes in degrees n if iopt<0 (Acceptable range: -90. to 90.)
[out]	nret	Number of valid points computed.
[out]	crot	Optional clockwise vector rotation cosines.
[out]	srot	Optional clockwise vector rotation sines.
[out]	xlon	Optional dx/dlon in 1/degrees.
[out]	xlat	Optional dx/dlat in 1/degrees.
[out]	ylon	Optional dy/dlon in 1/degrees.
[out]	ylat	Optional dy/dlat in 1/degrees.
[out]	area	Optional area weights in m**2.

Author: Mark Iredell, George Gayno, Kyle Gerheiser

Date: Jan 2015

Definition at line 267 of file ip_rot_equid_cylind_egrid_mod.F90.

References clat, clat0, clatr, clon, dlats, dlons, irot, rerth, rlon0, rot_equid_cylind_egrid_error(), rot_equid_cylind_egrid_grid_area(), rot_equid_cylind_egrid_map_jacob(), rot_equid_cylind_egrid_vect_rot(), slat, slat0, and slatr.

◆ init_grib1()

subroutine ip_rot_equid_cylind_egrid_mod::init_grib1	(	class(ip_rot_equid_cylind_egrid), intent(inout)	self,
		type(grib1_descriptor), intent(in)	g1_desc
	)

private

Initializes a rotated equidistant cylindrical grid given a grib1_descriptor object.

Parameters

[in,out]	self	The grid to initialize
[in]	g1_desc	A grib1_descriptor

Author: Kyle Gerheiser

Date: July 2021

Definition at line 86 of file ip_rot_equid_cylind_egrid_mod.F90.

References ip_constants_mod::dpr.

◆ init_grib2()

subroutine ip_rot_equid_cylind_egrid_mod::init_grib2	(	class(ip_rot_equid_cylind_egrid), intent(inout)	self,
		type(grib2_descriptor), intent(in)	g2_desc
	)

private

Initializes a rotated equidistant cylindrical grid given a grib2_descriptor object.

Parameters

[in,out]	self	The grid to initialize
[in]	g2_desc	A grib2_descriptor

Author: Kyle Gerheiser

Date: July 2021

Definition at line 163 of file ip_rot_equid_cylind_egrid_mod.F90.

◆ rot_equid_cylind_egrid_error()

subroutine ip_rot_equid_cylind_egrid_mod::rot_equid_cylind_egrid_error	(	integer, intent(in)	IOPT,
		real, intent(in)	FILL,
		real, dimension(npts), intent(out)	RLAT,
		real, dimension(npts), intent(out)	RLON,
		real, dimension(npts), intent(out)	XPTS,
		real, dimension(npts), intent(out)	YPTS,
		integer, intent(in)	NPTS
	)

private

Error handler.

UPON AN ERROR, THIS SUBPROGRAM ASSIGNS A "FILL" VALUE TO THE OUTPUT FIELDS.

Program History Log

Date	Programmer	Comments
2015-07-13	GAYNO	Initial version
2015-09-17	GAYNO	Rename as "rot_equid_cylind_egrid_error"

Parameters

[in]	iopt	option flag 1 to compute earth coords of selected grid coords -1 to compute grid coords of selected earth coords
[in]	fill	fill value to set invalid output data (must be impossible value; suggested value: -9999.)
[out]	rlat	(npts) earth latitudes in degrees n if iopt<0
[out]	rlon	(npts) earth longitudes in degrees e if iopt<0
[out]	xpts	(npts) grid x point coordinates if iopt>0
[out]	ypts	(npts) grid y point coordinates if iopt>0
[in]	npts	maximum number of coordinates

Author: GAYNO

Date: 2015-07-13

Definition at line 482 of file ip_rot_equid_cylind_egrid_mod.F90.

Referenced by gdswzd_rot_equid_cylind_egrid().

◆ rot_equid_cylind_egrid_grid_area()

subroutine ip_rot_equid_cylind_egrid_mod::rot_equid_cylind_egrid_grid_area	(	real, intent(in)	FILL,
		real, intent(out)	AREA
	)

private

Computes the grid box area for a rotated equidistant cylindrical grid.

Parameters

[in]	fill	Fill value for undefined points.
[out]	area	Area weights in m^2.

Author: George Gayno

Date: Jan 2015

Definition at line 587 of file ip_rot_equid_cylind_egrid_mod.F90.

References clatr, dlats, dlons, and rerth.

Referenced by gdswzd_rot_equid_cylind_egrid().

◆ rot_equid_cylind_egrid_map_jacob()

subroutine ip_rot_equid_cylind_egrid_mod::rot_equid_cylind_egrid_map_jacob	(	real, intent(in)	FILL,
		real, intent(in)	RLON,
		real, intent(out)	XLON,
		real, intent(out)	XLAT,
		real, intent(out)	YLON,
		real, intent(out)	YLAT
	)

private

Computes the map jacobians for a rotated equidistant cylindrical grid.

Parameters

[in]	fill	Fill value for undefined points.
[in]	rlon	Longitude in degrees.
[out]	xlon	dx/dlon in 1/degrees.
[out]	xlat	dx/dlat in 1/degrees.
[out]	ylon	dy/dlon in 1/degrees.
[out]	ylat	dy/dlat in 1/degrees.