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compute_sections.f90 in trunk/NEMOGCM/TOOLS/SECTIONS_DIADCT/src – NEMO

source: trunk/NEMOGCM/TOOLS/SECTIONS_DIADCT/src/compute_sections.f90 @ 3294

Last change on this file since 3294 was 3294, checked in by rblod, 13 years ago

Merge of 3.4beta into the trunk
  • Property svn:executable set to *
File size: 33.7 KB
Line 
1MODULE compute_sections
2   !!=====================================================================
3   !!                       ***  MODULE  diadct  ***
4   !! Ocean diagnostics: Compute the transport through a section
5   !!
6   !! History: 2011: Clement Bricaud, Mercator-Ocean
7   !!
8   !!===============================================================
9   !! * Modules used
10   USE declarations 
11   USE sections_tools
12 
13   IMPLICIT NONE
14   PRIVATE
15
16   !! * Routine accessibility
17   PUBLIC compsec
18   
19   !! * Module variables
20 
21CONTAINS
22
23  SUBROUTINE compsec(jsec,sec,lkdebug)         
24     !!---------------------------------------------------------------------
25     !!                     ***  ROUTINE compsec  ***
26     !!
27     !!  ** Purpose : Compute the series of mesh points that represent the section
28     !!               defined by its extremities.
29     !!
30     !!  ** Method  :
31     !!          I.   Find which cells of the mesh the section is crossing
32     !!          II.  Classification of the intersections mesh/section
33     !!                  -first  classification west to east         
34     !!                  -second classification south to north
35     !!          III. Find extremities of section in the mesh
36     !!          IV.  Find the series of mesh points that form the section
37     !!  ** Input: sec : the section to compute
38     !!
39     !!  ** Output:
40     !!---------------------------------------------------------------------
41     !! * Arguments
42     INTEGER,INTENT(IN)           :: jsec    ! number of the section
43     TYPE(SECTION), INTENT(INOUT) :: sec     ! information about the section
44     LOGICAL ,INTENT(IN)          :: lkdebug ! debug or not debug this section
45
46     !! * Local variables
47     INTEGER :: &
48        ji,jj            ,     & ! dummy loop argument
49        jseg             ,     & ! loop on segments that form the section   
50        nb_inmesh        ,     & ! number of intersections between the section and the mesh
51        nmesh                    ! number of cells in processor domain
52     INTEGER :: itest , jtest    ! dummy integer
53     REAL(wp)      :: &
54        zdistEst   , zdistNorth , zdistWest , zdistSouth ,  &! temporary scalars
55        zdistEst2  , zdistNorth2, zdistWest2, zdistSouth2,  &! temporary scalars
56        zdistEst3  , zdistNorth3, zdistWest3, zdistSouth3,  &! temporary scalars
57        zdistFirst , zdistLast  , zdistref  ,               &! temporary scalars
58        zdistante  , zdistante2 , zdistnew  , zdistnew2  ,  &! temporary scalars
59        zdeltai    , zdeltaj                                 ! temporary scalars
60     LOGICAL :: & 
61        ll_overlap_sec_left = .FALSE. , ll_overlap_sec_right = .FALSE. ,&! temporary logical
62        ll_date_domain_left = .FALSE. , ll_date_domain_right = .FALSE. ,&! temporary logical
63        ll_overlap_sec      = .FALSE. , ll_date_domain       = .FALSE. ,&! temporary logical
64        ll_test             = .FALSE.                                    ! temporary logical
65     LOGICAL :: lest, lwest, lnorth, lsouth
66     LOGICAL :: l_oldmethod
67     CHARACTER(len=120) :: cltmp
68     TYPE(COORD_SECTION) :: &
69        coord_a   , coord_b  , coord_d ,  coord_t ,               &!temporary point (long/lat)
70        coordFirst, coordLast, coordTemp                           !        "
71     TYPE(COORD_SECTION), DIMENSION(nb_point_max) :: coordSec      !intersections mesh/section   
72     TYPE(POINT_SECTION) :: &
73        endingPoint, prevPoint , nextPoint,           &!temporary point (I/J)
74        SouthPoint , NorthPoint, EstPoint , WestPoint  !        "
75     !!---------------------------------------------------------------------
76     IF( jsec==1 )THEN
77          PRINT*,'                '
78          PRINT*,'COMPUTE SECTIONS'
79          PRINT*,'----------------'
80     ENDIF
81
82     !debug
83     CALL write_debug(jsec,'compute section:')
84     CALL write_debug(jsec,'================')
85
86
87     !==================!
88     !0. Initializations!
89     !==================!
90     
91     nmesh       = jpi*jpj          ! number of cells in processor domain
92     nb_inmesh   = 0                ! initialize number of intersections between section and the mesh
93     zdistEst  =0. ; zdistNorth=0. ; zdistWest=0. ; zdistSouth=0.   ! temporary scalars
94     zdistFirst=0. ; zdistLast =0.                                  ! temporary scalars
95     zdistante =0. ; zdistante2=0. ; zdistnew=0.  ; zdistnew2=0.    ! temporary scalars
96     zdeltai=0.    ; zdeltaj=0. 
97     coord_a     = COORD_SECTION( 0., 0. ) ; coord_b    = COORD_SECTION( 0., 0. )
98     coord_d     = COORD_SECTION( 0., 0. ) ; coord_t    = COORD_SECTION( 0., 0. ) 
99     coordFirst  = COORD_SECTION( 0., 0. ) ; coordLast  = COORD_SECTION( 0., 0. )
100     coordTemp   = COORD_SECTION( 0., 0. ) ; coordSec   = COORD_SECTION( 0., 0. )
101     endingPoint = POINT_SECTION( -1, -1 ) 
102     prevPoint   = POINT_SECTION( -1, -1 ) ; nextPoint   = POINT_SECTION( -1, -1 )
103     SouthPoint  = POINT_SECTION( -1, -1 ) ; NorthPoint  = POINT_SECTION( -1, -1 )
104     EstPoint    = POINT_SECTION( -1, -1 ) ; WestPoint   = POINT_SECTION( -1, -1 )
105
106     !===========================================================!   
107     !I. Find which cells of the mesh the section is  crossing  !
108     !===========================================================!
109
110     !loop on the mesh
111     DO jj=2,jpj
112        DO ji=2,jpi
113           !-----------------------------------------------------------
114           !For each cell of the mesh, we find the intersection between
115           !the section and the cell as described below:
116           !The cell is defined by 4 points A B C D
117           !and the section by S1 and S2
118           !
119           !Section\    ________
120           !        \ B|        |
121           !         \ |        |
122           !          \|one cell|
123           !      .....\        |
124           !           |\       |
125           !           | \      |
126           !          A|__\_____|D
127           !       ........\
128           !----------------\-------------------------------------------
129
130           !definition of points A,B,D (we don't need C)
131           coord_a = COORD_SECTION( glamf(ji-1,jj-1) ,gphif(ji-1,jj-1) )
132           coord_b = COORD_SECTION( glamf(ji-1,jj)   ,gphif(ji-1,jj)   )
133           coord_d = COORD_SECTION( glamf(ji,jj-1)   ,gphif(ji,jj-1)   )
134 
135           !size of the cell
136           zdeltai= glamf(ji-1,jj) - glamf(ji-1,jj-1) !zdeltai=[AB]
137           zdeltaj= gphif(ji,jj-1) - gphif(ji-1,jj-1) !zdeltaj=[AD]
138           
139           !intersection section/[AB]=?
140           coordTemp     = intersec(sec,coord_a,coord_b)     !compute intersection
141 
142           IF( coordTemp%lon .NE. -9999 )THEN
143              IF( nb_inmesh+1 .GT. nb_point_max )THEN
144                 PRINT*,"WARNING diadct: nb_point_max needs to be greater than ", nb_inmesh
145              ELSE   
146                 nb_inmesh=nb_inmesh+1             
147                 coordSec(nb_inmesh) = coordTemp    !store the intersection's coordinates
148
149                 !We need to know if the section crosses the overlapping band.
150
151                 !Fist we look if there is an intersection mesh/section
152                 !just on the left of the overlapping band:
153                 IF( coordTemp%lon .GT. glamf(1,1)-5  .AND. coordTemp%lon .LT. glamf(1,1) ) & 
154                    & ll_overlap_sec_left  = .TRUE.
155                 !And we look if there is an intersection mesh/section
156                 !just on the right of the overlapping band:
157                 IF( coordTemp%lon .GT. glamf(jpi,1) .AND. coordTemp%lon .LT. glamf(1,1)+5 ) &
158                    & ll_overlap_sec_right = .TRUE.
159              ENDIF
160           ENDIF
161             
162           !intersection section/[AD]=?
163           coordTemp=intersec(sec,coord_a,coord_d)       !compute intersection
164           coordTemp%lon = coordTemp%lon !* zmask(ji,jj)-9999.*(1-zmask(ji,jj))
165           coordTemp%lat = coordTemp%lat !* zmask(ji,jj)-9999.*(1-zmask(ji,jj))
166
167           IF( coordTemp%lon .NE. -9999 )THEN
168              IF( nb_inmesh+1 .GT. nb_point_max )THEN
169                 PRINT*, "WARNING diadct: nb_point_max needs to be greater than ", nb_inmesh
170              ELSE 
171                 nb_inmesh=nb_inmesh+1
172                 coordSec(nb_inmesh)=coordTemp
173                   
174                 !We need to know if the section crosses the overlapping band:
175                 !same test as above
176                 IF( coordTemp%lon .GE. glamf(1,1)-3  .AND. coordTemp%lon .LE. glamf(1,1) ) &
177                      & ll_overlap_sec_left  = .TRUE.
178                 IF( coordTemp%lon .GE. glamf(jpi,1) .AND. coordTemp%lon .LE. glamf(jpi,1)+3) & 
179                      & ll_overlap_sec_right = .TRUE. 
180              ENDIF
181           ENDIF
182         
183           !We need to know if the domain crosses the date line:
184           !Fist, we search a mesh point that is just one the left of date line:
185           IF( glamf(ji-1,jj-1) .GT.  175 .AND. glamf(ji-1,jj-1) .LT.  180 ) &
186              & ll_date_domain_left = .TRUE.
187           !And we search a mesh point that is just one the right of date line:
188           IF( glamf(ji-1,jj-1) .GT. -180 .AND. glamf(ji-1,jj-1) .LT. -175 ) & 
189              & ll_date_domain_right = .TRUE.
190 
191        ENDDO
192     ENDDO !End of the loop on the mesh
193
194 
195     !Crossing section/overlapping band (we need to know it for later):
196     !-----------------------------------------------------------------
197     !If there is one intersection mesh/section just on the left of
198     !the overlapping band (ll_overlap_sec_left  = .TRUE.)
199     !AND there is one just the right of the overlapping band
200     !(ll_overlap_sec_right  = .TRUE.),
201     !so the section crosses the overlapping band.
202     ll_overlap_sec = ll_overlap_sec_left .AND. ll_overlap_sec_right 
203
204     !Crossing of the domain and the date line (we need to know it for later):
205     !------------------------------------------------------------------------
206     !If there is one point of the domain that is just on the left of the date line
207     !(ll_date_domain_left = .TRUE.) AND one point that is just on the right of the
208     !date line (ll_date_domain_right = .TRUE. )
209     !So the domain crosses the date line:
210     ll_date_domain = ll_date_domain_left .AND. ll_date_domain_right
211
212     !=====================================================!
213     ! II. Classification of the intersections mesh/section!
214     !=====================================================!
215
216     !   -first classification  west to east         
217     !   -second classification south to north       
218     !CAUTION: routine qcksrt doesn't work in the same way if the section
219     !and the domain crosse the date line (sec%ll_date_line=T and ll_date_domain=T)
220
221     IF( sec%ll_date_line .AND. ll_date_domain )THEN
222
223        !we add 360° to negative longitudes to have a good classification
224        DO jseg=1,nb_inmesh
225           IF( coordSec(jseg)%lon .LT. 0 ) coordSec(jseg)%lon=coordSec(jseg)%lon+360.
226        ENDDO
227        IF( sec%coordSec(1)%lon .NE. sec%coordSec(2)%lon ) THEN
228           CALL qcksrt(coordSec(:)%lon,coordSec(:)%lat,nb_inmesh)
229        ELSE
230           CALL qcksrt(coordSec(:)%lat,coordSec(:)%lon,nb_inmesh)
231        ENDIF
232        DO jseg=1,nb_inmesh
233           IF( coordSec(jseg)%lon .GT. 180 ) coordSec(jseg)%lon=coordSec(jseg)%lon-360.
234        ENDDO
235
236     ELSE     
237
238        IF( sec%coordSec(1)%lon .NE. sec%coordSec(2)%lon )THEN
239           CALL qcksrt(coordSec(:)%lon,coordSec(:)%lat,nb_inmesh)
240        ELSE
241           CALL qcksrt(coordSec(:)%lat,coordSec(:)%lon,nb_inmesh)
242        ENDIF
243
244     ENDIF
245
246     !debug
247     WRITE(cltmp,'(A20,i3.3)')'number intersections = ',nb_inmesh ; CALL write_debug(jsec,cltmp)
248     CALL write_debug(jsec,'List of intersections between grid and section: ')
249     DO jseg=1,nb_inmesh
250        WRITE(cltmp,'(i4.4,1X,2(f8.3,1X) )')jseg,coordSec(jseg) ;  CALL write_debug(jsec,cltmp)
251     ENDDO
252 
253     !=====================================================!
254     ! III. Find extremities of section in the mesh        !
255     !=====================================================!
256     !we can find section's extremities in the mesh only if
257     !there is intersection between section and mesh (nb_inmesh .ne. 0)
258
259     IF( nb_inmesh .ne. 0 )THEN
260        coordFirst       = coordSec(1)
261        coordLast        = coordSec(nb_inmesh) 
262        sec%nb_point     = nb_inmesh
263        sec%listPoint(1) = POINT_SECTION(-1,-1)
264        zdistante        = 1000.
265        zdistante2       = 1000.
266
267        !First, we find the point of the mesh that is the closest
268        !to the first intersection section/mesh (=coordFirst=coordSec(1)):
269        !this point will be called sec%listPoint(1).
270        !Then, we find the point of the mesh that is the closest
271        !to the last intersection section/mesh (coordLast=coordSec(nb_inmesh))
272        !this point will be called endingPoint.
273
274        DO jj=1,jpj
275           DO ji=1,jpi 
276              coord_t=COORD_SECTION(glamf(ji,jj),gphif(ji,jj))
277              zdistFirst = distance2(coord_t,coordFirst)
278              zdistLast = distance2(coord_t,coordLast)
279              IF( zdistFirst .LT. zdistante )THEN
280                 sec%listPoint(1) = POINT_SECTION(ji,jj)
281                 zdistante=zdistFirst
282              ENDIF
283              IF( zdistLast .LT. zdistante2 )THEN
284                 endingPoint = POINT_SECTION(ji,jj)
285                 zdistante2=zdistLast
286              ENDIF
287           ENDDO
288        ENDDO
289
290        IF( sec%listPoint(1)%I == endingPoint%I .AND. sec%listPoint(1)%J == endingPoint%J )THEN
291           sec%listPoint(1) = POINT_SECTION(-1,-1)
292           endingPoint      = POINT_SECTION(-1,-1)
293           coordFirst       = coordSec(1)
294           coordLast        = coordSec(2)
295           sec%nb_point     = 0
296        ENDIF
297
298     ELSE
299        !If there is no intersection section/mesh
300        sec%listPoint(1) = POINT_SECTION(-1,-1)
301        endingPoint      = POINT_SECTION(-1,-1)
302        coordFirst       = coordSec(1)
303        coordLast        = coordSec(2)
304        sec%nb_point     = 0
305     ENDIF 
306
307     !debug
308     CALL write_debug(jsec,"extremities of section in the grid : ")
309     ji=sec%listPoint(1)%I ; jj=sec%listPoint(1)%J
310     IF( sec%nb_point .ne. 0 )THEN
311        ji=sec%listPoint(1)%I ; jj=sec%listPoint(1)%J
312        WRITE(cltmp,'(A15,X,i4.4,X,i4.4,X,f8.3,X,f8.3)')'First point: ',sec%listPoint(1),glamf(ji,jj),gphif(ji,jj) 
313        CALL write_debug(jsec,cltmp)
314        ji=endingPoint%I ; jj=endingPoint%J
315        WRITE(cltmp,'(A15,X,i4.4,X,i4.4,X,f8.3,X,f8.3)')'Last  point: ',endingPoint,glamf(ji,jj),gphif(ji,jj)
316        CALL write_debug(jsec,cltmp)
317        !
318        coord_a=pointToCoordF(sec%listPoint(1)) ; coord_b=pointToCoordF(endingPoint)
319        ll_test = .FALSE.
320        IF ( ll_date_domain .AND. ABS( coord_a%lon - coord_b%lon ).GT. 180) ll_test= .TRUE.
321        zdistante=distance2(coord_a,coord_b ,ll_test )
322        WRITE(cltmp,'(A20,f10.3)' )'distance between IJ-extremities : ',zdistante
323        CALL write_debug(jsec,cltmp)
324        !
325        CALL write_debug(jsec,"Initial extremities : ") 
326        WRITE(cltmp,'( 2(f9.3),A3,2(f9.3) )')coordFirst,'---',coordLast
327        CALL write_debug(jsec,cltmp)
328        ll_test = .FALSE.
329        IF( ll_date_domain .AND. ABS(coordFirst%lon - coordLast%lon).GT. 180)ll_test= .TRUE.
330        zdistante=distance2(coordFirst,coordLast,ll_test)
331        WRITE(cltmp,'(A30,f10.3)')' distance between initial extremities : ',zdistante
332        CALL write_debug(jsec,cltmp)
333        CALL write_debug(jsec,"                  ")
334     ELSE
335        WRITE(cltmp,'(A50)' )"no intersection between section and mesh"
336     ENDIF
337
338     !==========================================================!
339     ! IV. Find the series of mesh points that form the section !
340     !==========================================================!
341     CALL write_debug(jsec,"Find the serie of mesh's points that form the section")
342
343     IF( sec%nb_point .ne. 0 )THEN
344
345        !The series of mesh points that form the section will 'link'
346        !sec%listPoint(1) to endingPoint: it will be stored in
347        !sec%listPoint(jseg)
348        !
349        !We take place on the first point (sec%listPoint(1))
350        ! a.  We find the 4 adjacent points (North, South, East, West)
351        ! b.  Compute distance between current point and endingPoint
352        ! c.  Compute distance between the 4 adjacent points and endingPoint
353        ! d.  Select the points which are closer to end-point than current point
354        ! e.1 If at least one point is selected, select the point which is closest to original section among selected points
355        ! e.2 If no point is selected, select the point which is the closest to end-point
356        ! f. save next point and direction of velocity.
357        ! g. Save nextPoint and go to nextPoint
358        !
359        !We get out of this loop if:
360        !    - we are on endingPoint
361        !    - the number of points (jseg) that link sec%listPoint(1) to endingPoint is
362        !      twice greater than number of section/mesh intersection (nb_inmesh):
363        !      it could be possible if thr algorithm can't link endingPoint (bug).
364
365        !initialize distnew value (with distance between section's extremities)
366        zdistnew  = distance2(coordFirst,coordLast,sec%ll_date_line) 
367        prevPoint  = POINT_SECTION(0,0)
368        jseg       = 1
369
370        DO WHILE ( (  sec%listPoint(jseg)%I .NE.  endingPoint%I    &
371                 .OR. sec%listPoint(jseg)%J .NE. endingPoint%J   ) &
372                 .AND. jseg .LT. nb_inmesh + 1 .AND. sec%listPoint(jseg)%I .GT. 0  )         
373   
374           ! a. find the 4 adjacent points (North, South, East, West)
375           !---------------------------------------------------------
376           SouthPoint = POINT_SECTION(sec%listPoint(jseg)%I,sec%listPoint(jseg)%J-1)
377           NorthPoint = POINT_SECTION(sec%listPoint(jseg)%I,sec%listPoint(jseg)%J+1)
378           WestPoint  = POINT_SECTION(sec%listPoint(jseg)%I-1,sec%listPoint(jseg)%J)
379           EstPoint   = POINT_SECTION(sec%listPoint(jseg)%I+1,sec%listPoint(jseg)%J)
380
381           !debug
382           CALL write_debug(jsec,"---------------")
383           WRITE(cltmp,100)'Current points: ',sec%listPoint(jseg), & 
384                         glamf(sec%listPoint(jseg)%I,sec%listPoint(jseg)%J), &
385                         gphif(sec%listPoint(jseg)%I,sec%listPoint(jseg)%J)
386           CALL write_debug(jsec,cltmp)
387           CALL write_debug(jsec,"E/W/N/S points")
388           WRITE(cltmp,102)EstPoint,WestPoint,NorthPoint,SouthPoint
389           CALL write_debug(jsec,cltmp)
390           itest=MIN(MAX(EstPoint%I,0),jpi+1) ; jtest=MIN(MAX(EstPoint%J,0),jpj+1)
391           IF( itest .NE. 0 .AND. itest .NE. jpi+1 .AND. jtest .NE. 0 .AND. jtest .NE. jpj+1 )THEN
392              WRITE(cltmp,101)'Est',glamf(itest,jtest),gphif(itest,jtest)
393              CALL write_debug(jsec,cltmp)
394           ELSE
395              CALL write_debug(jsec,"Est point out of domain")
396           ENDIF
397           !
398           itest=MIN(MAX(WestPoint%I,0),jpi+1) ; jtest=MIN(MAX(WestPoint%J,0),jpj+1)
399           IF( itest .NE. 0 .AND. itest .NE. jpi+1 .AND. jtest .NE. 0 .AND. jtest .NE. jpj+1 )THEN
400              WRITE(cltmp,101)'West',glamf(itest,jtest),gphif(itest,jtest)
401              CALL write_debug(jsec,cltmp)
402           ELSE
403              CALL write_debug(jsec,"West point out of domain")
404           ENDIF
405           !
406           itest=MIN(MAX(NorthPoint%I,0),jpi+1) ; jtest=MIN(MAX(NorthPoint%J,0),jpj+1)
407           IF( itest .NE. 0 .AND. itest .NE. jpi+1 .AND. jtest .NE. 0 .AND. jtest .NE. jpj+1 )THEN
408              WRITE(cltmp,101)'North',glamf(itest,jtest),gphif(itest,jtest)
409              CALL write_debug(jsec,cltmp)
410           ELSE
411              CALL write_debug(jsec,"North point out of domain")
412           ENDIF
413           !
414           itest=MIN(MAX(SouthPoint%I,0),jpi+1) ; jtest=MIN(MAX(SouthPoint%J,0),jpj+1)
415           IF( itest .NE. 0 .AND. itest .NE. jpi+1 .AND. jtest .NE. 0 .AND. jtest .NE. jpj+1 )THEN
416              WRITE(cltmp,101)'South',glamf(itest,jtest),gphif(itest,jtest)
417              CALL write_debug(jsec,cltmp)
418           ELSE
419              CALL write_debug(jsec,"South point out of domain")
420           ENDIF
421           !
422           !
423100 FORMAT ( A15,2(i4.4," "),2(f8.3," ") )
424101 FORMAT ( A6,2(f7.3," "))
425102 FORMAT ( "E ",i4.4,' ',i4.4,"//W ",i4.4,' ',i4.4,"//N ",i4.4,' ',i4.4,"//S ",i4.4,' ',i4.4 )
426
427               
428           !Either we are at an end-point
429           !--------------------
430           IF(      SouthPoint%I==endingPoint%I .AND. SouthPoint%J==endingPoint%J )THEN
431               jseg = jseg+1 ; sec%listPoint(jseg) = SouthPoint
432           ELSE IF( NorthPoint%I==endingPoint%I .AND. NorthPoint%J==endingPoint%J )THEN
433               jseg = jseg+1 ; sec%listPoint(jseg) = NorthPoint
434           ELSE IF(  WestPoint%I==endingPoint%I .AND.  WestPoint%J==endingPoint%J )THEN
435               jseg = jseg+1 ; sec%listPoint(jseg) = WestPoint
436           ELSE IF(   EstPoint%I==endingPoint%I .AND.   EstPoint%J==endingPoint%J )THEN
437               jseg = jseg+1 ; sec%listPoint(jseg) = EstPoint
438
439           ELSE
440           !Else we are NOT on end-point
441           !------------------------
442
443              ! b. distance between current point and endingPoint
444              !--------------------------------------------------
445              zdistante = zdistnew
446
447              ! c. compute distance between the 4 adjacent points and endingPoint
448              !------------------------------------------------------------------
449              ! BE CAREFUL! When the domain crosses the date line (ll_date_domain):
450              !
451              ! When we will compute distances between W/E/S/N points and endingPoint,
452              ! we have to check if theses 4 lines crosses the date line
453              ! (test: ABS(coordTemp%lon - coordLast%lon).GT. 180)
454              !
455              ! If one of these lines crosses the date line, we have to add 360°
456              ! to the longitudes of the extremities to compute the distance through
457              ! the date line and not around the Earth.
458       
459              ! c.1 compute distWest: distance between west point and endingPoint
460              !----------------------
461              zdistWest2 = 99999999.9 ;  zdistWest3 = 99999999.9 
462              IF( sec%listPoint(jseg)%I .NE. 1 )THEN
463                 !When we are on the west side of the mesh (i=1),we can't go to the west.
464                 coordTemp = pointToCoordF(WestPoint) 
465                 ll_test = .FALSE.
466                 IF( ll_date_domain .AND. ABS(coordTemp%lon - coordLast%lon).GT. 180 )ll_test = .TRUE.
467                 zdistWest2  = distance2(pointToCoordF(WestPoint) ,coordLast ,ll_test)
468              ENDIF
469
470              ! c.2 compute distEst: distance between east point and endingPoint
471              !---------------------
472              zdistEst2 = 99999999.9 ;  zdistEst3 = 99999999.9
473              IF( sec%listPoint(jseg)%I .EQ. jpi )THEN
474                 !We test if the current point is on the east side of the mesh
475                 ! The method is done such that we go toward east to link
476                 ! sec%listPoint(1) to endingPoint.
477                 ! So, if the section crosses the overlapping band (ll_overlap_sec=T),
478                 ! we won't have to stop if the current point is on the EAST side of the mesh:
479                 ! we have to follow the construction of the section on the
480                 ! WEST side of the mesh
481                 IF( ll_overlap_sec  )THEN
482                    !section crosses the overlapping band
483                    !So EastPoint is on the west side of the mesh
484                    EstPoint = POINT_SECTION(3,sec%listPoint(jseg)%J)
485                    zdistEst2= distance2(pointToCoordF(EstPoint)  ,coordLast ,.FALSE.)
486                 ENDIF
487              ELSE
488                 coordTemp = pointToCoordF(EstPoint) 
489                 ll_test = .FALSE.
490                 IF( ll_date_domain .AND. ABS(coordTemp%lon - coordLast%lon).GT. 180 )ll_test= .TRUE.
491                 zdistEst2 = distance2(pointToCoordF(EstPoint)  ,coordLast ,ll_test )
492              ENDIF
493
494              ! c.3 compute distSouth: distance between south point and endingPoint
495              !-----------------------
496              zdistSouth2 = 99999999.9 ; zdistSouth3 = 99999999.9
497              IF( sec%listPoint(jseg)%J .NE. 1 )THEN
498                 !When we are on the south side of the mesh (j=1),we can't go to the south.
499                 coordTemp=pointToCoordF(SouthPoint)
500                 ll_test = .FALSE.
501                 IF( ll_date_domain .AND. ABS(coordTemp%lon - coordLast%lon).GT. 180 )ll_test= .TRUE.
502                    zdistSouth2 = distance2(pointToCoordF(SouthPoint),coordlast ,ll_test )
503              ENDIF
504
505              ! c.4 compute distNorth: distance between north and endingPoint
506              !-----------------------
507              zdistNorth2 = 99999999.9 ; zdistNorth3 = 99999999.9 
508              IF( sec%listPoint(jseg)%J .NE. jpj )THEN
509                 !When we are on the north side of the mesh (j=jpj),we can't go to the south.
510                 coordTemp=pointToCoordF(NorthPoint)
511                 ll_test = .FALSE.
512                 IF( ll_date_domain .AND. ABS(coordTemp%lon - coordLast%lon).GT. 180 )ll_test= .TRUE.
513                 zdistNorth2 = distance2(pointToCoordF(NorthPoint),coordlast ,ll_test )
514              ENDIF
515
516              ! d. select the points which are closer to end-point than current point
517              !----------------------------------------------------------------------
518              zdistref=distance2(pointToCoordF(sec%listPoint(jseg)),coordlast ,ll_test )
519              WRITE(cltmp,'( A56,f10.3 )' )'distance between actual point and last point: zdistref = ',zdistref
520              CALL write_debug(jsec,cltmp)
521              lest   = .FALSE. ; IF( zdistEst2   .LE. zdistref ) lest  = .TRUE.
522              lwest  = .FALSE. ; IF( zdistwest2  .LE. zdistref ) lwest = .TRUE.
523              lnorth = .FALSE. ; IF( zdistnorth2 .LE. zdistref ) lnorth= .TRUE.
524              lsouth = .FALSE. ; IF( zdistsouth2 .LE. zdistref ) lsouth= .TRUE.
525
526              !debug
527              IF( .NOT. lest   )CALL write_debug(jsec,'Est   point eliminated')
528              IF( .NOT. lwest  )CALL write_debug(jsec,'West  point eliminated')
529              IF( .NOT. lnorth )CALL write_debug(jsec,'North point eliminated')
530              IF( .NOT. lsouth )CALL write_debug(jsec,'South point eliminated')
531
532              l_oldmethod = .FALSE.
533
534              IF( ( COUNT((/lest/))+COUNT((/lwest/))+COUNT((/lnorth/))+COUNT((/lsouth/)) ) .NE. 0 )THEN
535
536                 ! e.1 If at least one point is selected, select the point
537                 !     which is the closest to original section among selected points
538                 !-------------------------------------------------------------------
539
540                 zdistWest3  = 9999999.9
541                 IF( lwest )zdistWest3  = &
542                    distance3(pointToCoordF(sec%listPoint(1)),pointToCoordF(WestPoint) ,pointToCoordF(endingPoint) ,lkdebug )
543                 zdistEst3   = 9999999.9
544                 IF( lest )zdistEst3   =  &
545                    distance3(pointToCoordF(sec%listPoint(1)),pointToCoordF(EstPoint)  ,pointToCoordF(endingPoint) ,lkdebug )
546                 zdistSouth3 = 9999999.9
547                 IF( lsouth )zdistSouth3 = &
548                    distance3(pointToCoordF(sec%listPoint(1)),pointToCoordF(SouthPoint),pointToCoordF(endingPoint) ,lkdebug )
549                 zdistNorth3 = 9999999.9
550                 IF( lnorth )zdistNorth3 = &
551                    distance3(pointToCoordF(sec%listPoint(1)),pointToCoordF(NorthPoint),pointToCoordF(endingPoint) ,lkdebug )
552
553                 zdistEst3   = zdistEst3   + (1-COUNT((/lest/))  )*9999999.9
554                 zdistWest3  = zdistWest3  + (1-COUNT((/lwest/)) )*9999999.9
555                 zdistNorth3 = zdistNorth3 + (1-COUNT((/lnorth/)))*9999999.9
556                 zdistSouth3 = zdistSouth3 + (1-COUNT((/lsouth/)))*9999999.9
557
558                 zdistnew = MIN(zdistEst3,zdistWest3,zdistnorth3,zdistSouth3)
559
560              ELSE 
561
562                 ! e.2 If no point is selected, select the point which is the closest to end-point
563                 !--------------------------------------------------------------------------------
564                 l_oldmethod = .TRUE.
565
566                 !debug
567                 WRITE(cltmp,'(A30,i3.3)' )'SEARCH NEW POINT WITH OLD METHOD: ',jsec
568                 CALL write_debug(jsec,cltmp)
569                   
570                 !be careful! we can't go backward.
571                 zdistNorth = zdistNorth2    ; zdistSouth = zdistSouth2
572                 zdistEst   = zdistEst2      ; zdistWest  = zdistWest2 
573
574                 IF(     prevPoint%I .EQ. NorthPoint%I .AND. prevPoint%J .EQ. NorthPoint%J) THEN
575                     zdistnew = MIN(zdistEst,zdistWest,zdistSouth)
576                 ELSE IF(prevPoint%I .EQ. SouthPoint%I .AND. prevPoint%J .EQ. SouthPoint%J) THEN
577                    zdistnew = MIN(zdistEst,zdistWest,zdistNorth)
578                 ELSE IF(prevPoint%I .EQ. WestPoint%I  .AND. prevPoint%J .EQ. WestPoint%J ) THEN
579                    zdistnew = MIN(zdistEst,zdistNorth,zdistSouth)
580                 ELSE IF(prevPoint%I .EQ. EstPoint%I   .AND. prevPoint%J .EQ. EstPoint%J  ) THEN
581                    zdistnew = MIN(zdistWest,zdistNorth,zdistSouth)
582                 ELSE
583                    zdistnew = MIN(zdistEst,zdistWest,zdistNorth,zdistSouth)
584                 ENDIF             
585
586              ENDIF
587
588              !debug
589              WRITE(cltmp,'(A11, f8.3)')'zdistref = ',zdistref
590              CALL write_debug(jsec,cltmp)
591              WRITE(cltmp, 103         )'distance2 :',zdistEst2,zdistWest2,zdistNorth2,zdistSouth2 
592              CALL write_debug(jsec,cltmp)
593              WRITE(cltmp, 103         )'distance3 :',zdistEst3,zdistWest3,zdistNorth3,zdistSouth3
594              CALL write_debug(jsec,cltmp)
595              WRITE(cltmp,'(A11, f8.3)')"zdistnew = ",zdistnew
596              CALL write_debug(jsec,cltmp)
597
598103 FORMAT (A12,"E",f12.3," W",f12.3," N",f12.3," S",f12.3)
599
600              !f. save next point and direction of velocity.
601              !---------------------------------------------
602              !nextPoint will be the one which is the closest to endingPoint.
603              !sec%direction will be direction between current point and nextPoint:
604              !It will be used to compute velocity through the segment [CurrentPoint,nextPoint}:
605              !                 
606              !A:Current Point    NorthPoint(I,J+1)   Nextpoint=NorthPoint(I,J+1) => sec%direction=3
607              !                   |                   Nextpoint=SouthPoint(I,J-1) => sec%direction=2   
608              !                   |                   Nextpoint=WestPoint(I-1,J)  => sec%direction=0   
609              !                   |==>V(I,J+1)        Nextpoint=EastPoint(I+1,J)  => sec%direction=1
610              !            U(I,J) |       U(I+1,J)
611              !            ^      |       ^
612              !   West_____|______A_______|_____EstPoint
613              !   Point           |(I,J)        (I+1,J) 
614              !   (I-1,J)         |               
615              !                   |==>V(I,J)
616              !                   |
617              !              SoutPoint(I,J-1)
618              IF( l_oldmethod )THEN
619                 IF( zdistnew == zdistWest )      THEN
620                      sec%direction(jseg)=0 ; nextPoint = WestPoint
621                 ELSE IF( zdistnew == zdistEst )  THEN
622                      sec%direction(jseg)=1 ; nextPoint = EstPoint
623                 ELSE IF( zdistnew == zdistSouth )THEN
624                      sec%direction(jseg)=2 ; nextPoint = SouthPoint
625                 ELSE IF( zdistnew == zdistNorth )THEN
626                      sec%direction(jseg)=3 ; nextPoint= NorthPoint
627                 ENDIF
628              ELSE
629                 IF( zdistnew == zdistWest3 )      THEN
630                      sec%direction(jseg)=0 ; nextPoint = WestPoint
631                 ELSE IF( zdistnew == zdistEst3 )  THEN
632                      sec%direction(jseg)=1 ; nextPoint = EstPoint
633                 ELSE IF( zdistnew == zdistSouth3 )THEN
634                      sec%direction(jseg)=2 ; nextPoint = SouthPoint
635                 ELSE IF( zdistnew == zdistNorth3 )THEN
636                      sec%direction(jseg)=3 ; nextPoint= NorthPoint
637                 ENDIF
638              ENDIF
639
640              WRITE(cltmp,'(A11, 2(i4.4,1X) )')'nextPoint = ', nextPoint
641              CALL write_debug(jsec,cltmp)
642       
643              !f. Save nextPoint and go to nextPoint
644              !-------------------------------------
645              prevPoint = sec%listPoint(jseg)
646              jseg = jseg+1                   !increment of number of segments that form the section
647              sec%listPoint(jseg) = nextPoint !Save next point
648   
649           ENDIF ! southP/northP/WestP/EstP == endingpoint ?
650
651        ENDDO                  !End of loop on jseg
652        sec%nb_point = jseg    !Save the number of segments that form the section
653
654
655     ELSE ! isec%nb_point == 0
656        DO jseg=1,nb_point_max 
657           sec%listPoint(:)=POINT_SECTION(0,0)
658        ENDDO
659        sec%direction(:)=0.
660        sec%nb_point = 0
661     ENDIF
662
663     !debug     
664     IF( sec%nb_point .ne. 0 )THEN
665        CALL write_debug(jsec,"-------------------------------------")
666        CALL write_debug(jsec,"list of points in the grid : ")
667        DO jseg=1,sec%nb_point 
668           ji=sec%listPoint(jseg)%I ; jj=sec%listPoint(jseg)%J
669           WRITE(cltmp, '(i4.4,X,i4.4,X,i4.4,X,f8.3,X,f8.3)' )jseg,ji,jj,glamf(ji,jj),gphif(ji,jj)
670           CALL write_debug(jsec,cltmp)
671        ENDDO
672   
673        !test if we are an end-point
674        IF( sec%listPoint(sec%nb_point)%I .NE. endingPoint%J .AND. sec%listPoint(sec%nb_point)%J .NE. endingPoint%J )THEN   
675           PRINT*,TRIM(sec%name)," NOT ARRIVED TO endingPoint FOR jsec =  ",jsec
676        ENDIF
677     ENDIF
678
679     !now compute new slopeSection with ij-coordinates of first and last point
680     sec%slopeSection = 0  ! default value
681     IF( sec%nb_point .ne. 0 )THEN
682        IF (  sec%listPoint(sec%nb_point)%I .NE.  sec%listPoint(1)%I ) THEN
683           sec%slopeSection = ( sec%listPoint(sec%nb_point)%J - sec%listPoint(1)%J ) /  &
684                              ( sec%listPoint(sec%nb_point)%I - sec%listPoint(1)%I )     
685        ELSE
686           sec%slopeSection = 10000._wp
687        ENDIF
688     ENDIF
689 
690  END SUBROUTINE compsec
691
692END MODULE compute_sections 
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