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C Copyright 1981-2007 ECMWF
C
C Licensed under the GNU Lesser General Public License which
C incorporates the terms and conditions of version 3 of the GNU
C General Public License.
C See LICENSE and gpl-3.0.txt for details.
C
INTEGER FUNCTION HGENGG(AREA,POLE,KGNNEW,HGTYPE,KNPTS,GNLATS,
X IGSIZE,RLAT,RLON,NUMPTS)
C
C---->
C**** HGENGG
C
C Purpose
C -------
C
C This routine calculates the original latitude and longitude
C values (before rotation) for a rotated gaussian grid.
C
C
C Interface
C ---------
C
C IRET = HGENGG(AREA,POLE,KGNNEW,HGTYPE,KNPTS,IGSIZE,
C X RLAT,RLON,NUMPTS)
C
C
C Input parameters
C ----------------
C
C AREA - Limits of area (N/W/S/E)
C POLE - Pole of rotation (lat/long)
C KGNNEW - Gaussian number for field
C HGTYPE - Type of new gaussian field
C 'F' = full, ie regular
C 'R' = reduced, ie quasi-regular
C KNPTS - Array containing number of points at each latitude
C GNLATS - Array containing list of gaussian latitudes
C IGSIZE - The size of the array to fill with the gaussian field
C NUMPTWE - Calculate number of grid pts in range from west to east
C
C
C Output parameters
C -----------------
C
C RLAT - Vector of orginal latitude values for the points in
C the rotated grid.
C RLON - Vector of orginal longitude values for the points in
C the rotated grid.
C NUMPTS - Number of points in new field
C
C Returns 0 if function successful, non-zero otherwise.
C
C
C Common block usage
C ------------------
C
C None.
C
C
C Method
C ------
C
C The vector of points runs from West to East in rows, the rows
C run from North to South.
C
C
C Externals
C ---------
C
C INTLOG - Log error message.
C JDEBUG - Tests if debug output required.
C HLL2XYZ - Converts a latitude/longitude position to (x,y,z)
C wrt axes through the centre of the globe. The z-axis
C runs from the south to north pole. The x- and y-axes
C are in the plane of the equator with the x-axis
C pointing out through lat/long (0,0).
C YROTATE - Rotates the globe about the new y-axis.
C XYZ2LL - Converts an (x,y,z) position to a latitude/longitude.
C JMALLOC - Dynamically allocate memory
C JFREE - Free dynamically allocated memory
C
C
C Reference
C ---------
C
C None.
C
C
C Comments
C --------
C
C None.
C
C
C Author
C ------
C
C J.D.Chambers ECMWF February 2001
C
C
C Modifications
C -------------
C
C None.
C
C----<
C -----------------------------------------------------------------|
C* Section 0. Definition of variables.
C -----------------------------------------------------------------|
C
IMPLICIT NONE
C
#include "parim.h"
#include "nofld.common"
C
C Parameters
C
INTEGER JNORTH, JSOUTH, JWEST, JEAST, JW_E, JN_S, JLAT, JLON
REAL JSCALE
PARAMETER (JNORTH = 1 )
PARAMETER (JWEST = 2 )
PARAMETER (JSOUTH = 3 )
PARAMETER (JEAST = 4 )
PARAMETER (JW_E = 1 )
PARAMETER (JN_S = 2 )
PARAMETER (JLAT = 1 )
PARAMETER (JLON = 2 )
PARAMETER (JSCALE = 1000.0 )
C
C Function arguments
C
CHARACTER*1 HGTYPE
INTEGER KGNNEW,KNPTS(KGNNEW*2),IGSIZE,NUMPTS
REAL AREA(4),POLE(2),RLAT(*),RLON(*), GNLATS(KGNNEW*2)
C
C Local variables
C
INTEGER LOOP, LOOPI, LOOPO, IGRIDNI, NLON
INTEGER ISIZE, ISIZOLD, NBYTES
REAL GRID, X(1), Y(1), Z(1)
REAL RX(1), RY(1), RZ(1)
POINTER( IPX, X )
POINTER( IPY, Y )
POINTER( IPZ, Z )
POINTER( IPRX, RX )
POINTER( IPRY, RY )
POINTER( IPRZ, RZ )
C
DATA ISIZOLD/-1/
SAVE ISIZOLD,IPX,IPY,IPZ,IPRX,IPRY,IPRZ
C
C Externals
C
INTEGER NUMPTWE
#ifdef POINTER_64
INTEGER*8 JMALLOC
#else
INTEGER JMALLOC
#endif
C
C Statement functions
C
REAL A, B
LOGICAL SOUTHOF
SOUTHOF(A,B) = ((A) - (B)).GT.-1E-4
C
C -----------------------------------------------------------------|
C Section 1. Initialise.
C -----------------------------------------------------------------|
C
100 CONTINUE
C
HGENGG = 0
C
CALL JDEBUG()
C
C -----------------------------------------------------------------|
C Section 2. Calculate current grid latitudes and longitudes
C -----------------------------------------------------------------|
C
200 CONTINUE
C
GRID = 360.0 / REAL(KGNNEW*4)
IGRIDNI = NINT(GRID*JSCALE)
C
NUMPTS = 0
NOPCNT = 0
NONS = 0
NOWE = 0
NO1NS = 0
C
DO LOOPO = 1, KGNNEW*2
C
C Generate points inside the area only.
C
IF( SOUTHOF(AREA(JNORTH),GNLATS(LOOPO)).AND.
X SOUTHOF(GNLATS(LOOPO),AREA(JSOUTH)) ) THEN
C
IF( NO1NS.EQ.0 ) NO1NS = LOOPO
NONS = NONS + 1
C
C Grid step varies for a reduced (quasi-regular) gaussian grid
C
IF( HGTYPE.EQ.'R' ) THEN
GRID = 360.0 / REAL(KNPTS(LOOPO))
IGRIDNI = NINT(GRID*JSCALE)
ENDIF
C
NLON = NUMPTWE(AREA(JWEST),AREA(JEAST),GRID)
NOWE = NLON
DO LOOPI = 1, NLON
NUMPTS = NUMPTS + 1
RLAT(NUMPTS) = GNLATS(LOOPO)
RLON(NUMPTS) = AREA(JWEST)+REAL((LOOPI-1)*IGRIDNI)/JSCALE
ENDDO
ENDIF
ENDDO
C
C -----------------------------------------------------------------|
C Section 3. Get some space for rotating the lat/longs
C -----------------------------------------------------------------|
C
300 CONTINUE
C
NOPCNT = NUMPTS
ISIZE = NUMPTS
IF( ISIZE.GT.ISIZOLD ) THEN
C
IF( ISIZOLD.GT.0 ) CALL JFREE(IPX)
C
NBYTES = 6*ISIZE*JPRLEN
C
IPX = JMALLOC(NBYTES)
#ifdef hpR64
IPX = IPX/(1024*1024*1024*4)
#endif
IF( IPX.EQ.0 ) THEN
CALL INTLOG(JP_WARN,'HGENGG: Memory allocate fail',JPQUIET)
HGENGG = 1
GOTO 900
ENDIF
C
IPY = IPX + (ISIZE*JPRLEN)
IPZ = IPY + (ISIZE*JPRLEN)
IPRX = IPZ + (ISIZE*JPRLEN)
IPRY = IPRX + (ISIZE*JPRLEN)
IPRZ = IPRY + (ISIZE*JPRLEN)
C
ISIZOLD = ISIZE
C
ENDIF
C
C -----------------------------------------------------------------|
C Section 4. Calculate the lat/longs before rotation
C -----------------------------------------------------------------|
C
400 CONTINUE
C
C Convert the rotated row points lat/longs to (x,y,z) coordinates
C
CALL HLL2XYZ(RLAT,RLON,X,Y,Z,ISIZE)
C
C Rotate the rotated row points back through the original latitude
C rotation
C
CALL YROTATE(-(90.0+POLE(JLAT)),X,Y,Z,RX,RY,RZ,ISIZE)
C
C Convert the rotated row points adjusted (x,y,z) coordinates to
C lat/long in the original grid (but still containing the
C longitude rotation)
C
CALL XYZ2LL(RX,RY,RZ,RLAT,RLON,ISIZE)
C
C Adjust the rotated line longitudes to remove the longitude
C rotation
C
DO LOOP = 1, ISIZE
RLON(LOOP) = RLON(LOOP) + POLE(JLON)
IF( RLON(LOOP).LT.0.0 ) RLON(LOOP) = RLON(LOOP) + 360.0
IF( RLON(LOOP).GE.360.0 ) RLON(LOOP) = RLON(LOOP) - 360.0
ENDDO
C
C -----------------------------------------------------------------|
C Section 9. Return
C -----------------------------------------------------------------|
C
900 CONTINUE
C
RETURN
END
|
