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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 IGPOLEW(PIFELD, KIWE, POFELD, KOWE, KWEIND,
1 KWEDIST, KPR, KERR)
C
C---->
C**** *IGPOLEW*
C
C Purpose
C -------
C
C Calculates the values at the pole of a regular
C latitude/longitude wind field when the input is a Gaussian field.
C
C This routine is only used for a wind field.
C
C Interface
C ---------
C
C IERR = IGPOLEW(PIFELD, KIWE, POFELD, KOWE, KWEIND, KWEDIST,
C 1 KPR, KERR)
C
C Input parameters
C ----------------
C
C PIFELD - A "polar" row of the input field provided by the
C calling routine.
C
C KIWE - The number of points in the West-East direction in
C the input field.
C
C KOWE - The number of points in the West-East direction in
C the output field.
C
C KWEIND - This array contains the array offsets of the West
C and East points in the input array required for
C interpolation.
C
C KWEDIST - This array holds the distances to longitude values
C in the input field from the associated longitude
C values in the output field.
C
C KPR - The debug print switch.
C 0 , No debugging output.
C 1 , Produce debugging output.
C
C KERR - The error control flag.
C -ve, No error message. Return error code.
C 0 , Hard failure with error message.
C +ve, Print error message. Return error code.
C
C Output parameters
C -----------------
C
C POFELD - The corresponding "polar" row of the output field
C returned to the calling routine.
C
C Return value
C ------------
C
C The error indicator (INTEGER).
C
C Error and Warning Return Values
C
C None
C
C Common block usage
C ------------------
C
C None
C
C Externals
C ---------
C
C INTLOG(R) - Logs messages.
C
C Method
C ------
C
C A Gaussian field does not have a line of latitude at the pole
C so this routine performs a linear interpolation of points on the
C nearest Gaussian line and then puts these values into the output
C array. The intention is to provide U and V values at the pole
C which have a "directional" value.
C
C This method was originally implemented by
C
C K. RIDER * ECMWF * OCTOBER 1991.
C
C Reference
C ---------
C
C None
C
C Comments
C --------
C
C Program contains sections 0 to 2 and 9
C
C Author
C ------
C
C K. Fielding *ECMWF* Oct 1993
C
C Modifications
C -------------
C
C Allow for missing data values
C J.D.Chambers ECMWF August 2000
C
C----<
C -----------------------------------------------------------------|
C* Section 0. Definition of variables.
C -----------------------------------------------------------------|
C
IMPLICIT NONE
C
#include "parim.h"
#include "nifld.common"
C
C Function arguments
C
INTEGER KIWE, KOWE, KPR, KERR
INTEGER KWEIND(2, KOWE), KWEDIST(2, KOWE)
REAL PIFELD(KIWE), POFELD(KOWE)
C
C Local variables
C
INTEGER JOLON, COUNT
REAL ZLOW, ZHIGH
C
C Statement function
C
REAL A, B
LOGICAL NOTEQ
NOTEQ(A,B) = (ABS((A)-(B)).GT.(ABS(A)*1E-3))
C
C -----------------------------------------------------------------|
C* Section 1. Initialisation
C -----------------------------------------------------------------|
C
100 CONTINUE
C
IF( KPR.GE.1 ) CALL INTLOG(JP_DEBUG,'IGPOLEW: Section 1.',JPQUIET)
C
IGPOLEW = 0
C
IF( KPR.GE.1 ) THEN
CALL INTLOG(JP_DEBUG,'IGPOLEW: No.input fld longs = ',KIWE)
CALL INTLOG(JP_DEBUG,'IGPOLEW: No.output fld longs = ',KOWE)
ENDIF
C
C -----------------------------------------------------------------|
C* Section 2. Interpolation code for winds
C -----------------------------------------------------------------|
C
200 CONTINUE
C
IF( KPR.GE.1 ) CALL INTLOG(JP_DEBUG,'IGPOLEW: Section 2.',JPQUIET)
C
DO JOLON = 1, KOWE
C
C Compute weigths for west and east neighbours
C
ZLOW = REAL(KWEDIST(JP_I_E,JOLON)) /
X REAL(KWEDIST(JP_I_E,JOLON) + KWEDIST(JP_I_W,JOLON) )
C
ZHIGH = PPONE - ZLOW
C
C Count non-missing data values
C
IF( LIMISSV ) THEN
COUNT = 0
IF( NOTEQ(PIFELD(KWEIND(JP_I_W,JOLON)),RMISSGV) )
X COUNT = COUNT + 1
IF( NOTEQ(PIFELD(KWEIND(JP_I_E,JOLON)),RMISSGV) )
X COUNT = COUNT + 1
ELSE
COUNT = 2
ENDIF
C
C Interpolate using both neighbours if neither is missing
C
IF( COUNT.EQ.2 ) THEN
POFELD(JOLON) = ZLOW * PIFELD(KWEIND(JP_I_W,JOLON)) +
X ZHIGH * PIFELD(KWEIND(JP_I_E,JOLON))
C
C Set missing if all neighbours are missing
C
ELSE IF( COUNT.EQ.0 ) THEN
POFELD(JOLON) = RMISSGV
C
C Otherwise, use the nearest neighbour
C
ELSE IF( ZLOW.GT.ZHIGH ) THEN
POFELD(JOLON) = PIFELD(KWEIND(JP_I_W,JOLON))
ELSE
POFELD(JOLON) = PIFELD(KWEIND(JP_I_E,JOLON))
ENDIF
C
ENDDO
C
C -----------------------------------------------------------------|
C* Section 9. Return to calling routine. Format statements
C -----------------------------------------------------------------|
C
900 CONTINUE
C
IF( KPR.GE.1 ) CALL INTLOG(JP_DEBUG,'IGPOLEW: Section 9.',JPQUIET)
C
RETURN
END
|
