source: LMDZ6/trunk/libf/phylmd/rrtm/cpledn_mod.F90 @ 3312

Last change on this file since 3312 was 1990, checked in by Laurent Fairhead, 11 years ago

Corrections à la version r1989 pour permettre la compilation avec RRTM
Inclusion de la licence CeCILL_V2 pour RRTM


Changes to revision r1989 to enable RRTM code compilation
RRTM part put under CeCILL_V2 licence

  • Property copyright set to
    Name of program: LMDZ
    Creation date: 1984
    Version: LMDZ5
    License: CeCILL version 2
    Holder: Laboratoire de m\'et\'eorologie dynamique, CNRS, UMR 8539
    See the license file in the root directory
File size: 3.8 KB
Line 
1MODULE CPLEDN_MOD
2CONTAINS
3SUBROUTINE CPLEDN(KN,KDBLE,PX,DDX,KFLAG,PW,PXN,DDXN,PXMOD)
4
5!**** *CPLEDN* - Routine to compute the Legendre polynomial of degree N
6
7!     Purpose.
8!     --------
9!           Computes Legendre polynomial of degree N
10
11!**   Interface.
12!     ----------
13!        *CALL* *CPLEDN(KN,KDBLE,PX,DDX,KFLAG,PW,PXN,DDXN,PXMOD)*
14
15!        Explicit arguments :
16!        --------------------
17!              KN       :  Degree of the Legendre polynomial
18!              KDBLE    :  0, single precision
19!                          1, double precision
20!              PX       :  abcissa where the computations are performed
21!              DDX      :  id in double precision
22!              KFLAG    :  When KFLAG.EQ.1 computes the weights
23!              PW       :  Weight of the quadrature at PXN
24!              PXN      :  new abscissa (Newton iteration)
25!              DDXN     :  id in double precision
26!              PXMOD    :  PXN-PX
27
28!        Implicit arguments :
29!        --------------------
30!       None
31
32!     Method.
33!     -------
34!        See documentation
35
36!     Externals.
37!     ----------
38!        None
39
40!     Reference.
41!     ----------
42!        ECMWF Research Department documentation of the IFS
43
44!     Author.
45!     -------
46!        Mats Hamrud and Philippe Courtier  *ECMWF*
47
48!     Modifications.
49!     --------------
50!        Original : 87-10-15
51!        Michel Rochas, 90-08-30 (Lobatto+cleaning)
52!     ------------------------------------------------------------------
53
54
55
56USE PARKIND1  ,ONLY : JPIM     ,JPRB
57USE PARKIND2  ,ONLY : JPRH
58
59IMPLICIT NONE
60
61
62!     DUMMY INTEGER SCALARS
63INTEGER(KIND=JPIM) :: KDBLE
64INTEGER(KIND=JPIM) :: KFLAG
65INTEGER(KIND=JPIM) :: KN
66
67!     DUMMY REAL SCALARS
68REAL(KIND=JPRB) :: PW
69REAL(KIND=JPRB) :: PX
70REAL(KIND=JPRB) :: PXMOD
71REAL(KIND=JPRB) :: PXN
72
73
74REAL(KIND=JPRH) :: DDX,DDXN,DLX,DLK,DLKM1,DLKM2,DLLDN,DLXN,DLMOD
75REAL(KIND=JPRH) :: DLG,DLGDN
76
77INTEGER(KIND=JPIM), PARAMETER :: JPKS=KIND(PX)
78INTEGER(KIND=JPIM), PARAMETER :: JPKD=KIND(DDX)
79
80!     LOCAL INTEGER SCALARS
81INTEGER(KIND=JPIM) :: IZN, JN
82
83!     LOCAL REAL SCALARS
84REAL(KIND=JPRB) :: ZG, ZGDN, ZK, ZKM1, ZKM2, ZLDN, ZMOD, ZX, ZXN
85
86
87!      -----------------------------------------------------------------
88
89!*       1. Single precision computations.
90!           ------------------------------
91
92IZN = KN
93
94ZK = 0.0_JPRB
95DLK = 0.0_JPRB
96DLXN = 0.0_JPRB
97IF(KDBLE == 0)THEN
98
99!*       1.1   NEWTON ITERATION STEP.
100
101  ZKM2 = 1
102  ZKM1 = PX
103  ZX   = PX
104  DO JN=2,IZN
105    ZK = (REAL(2*JN-1,JPRB)*ZX*ZKM1-REAL(JN-1,JPRB)*ZKM2)/REAL(JN,JPRB)
106    ZKM2 = ZKM1
107    ZKM1 = ZK
108  ENDDO
109  ZKM1 = ZKM2
110  ZLDN = (REAL(KN,JPRB)*(ZKM1-ZX*ZK))/(1.0_JPRB-ZX*ZX)
111  ZMOD = -ZK/ZLDN
112  ZXN = ZX+ZMOD
113  PXN = ZXN
114  DDXN = REAL(ZXN,JPKD)
115  PXMOD = ZMOD
116
117!     ------------------------------------------------------------------
118
119!*         2.    Double precision computations.
120!                ------------------------------
121
122ELSE
123
124!*       2.1   NEWTON ITERATION STEP.
125
126  DLKM2 = 1.0_JPRB
127  DLKM1 = DDX
128  DLX = DDX
129  DO JN=2,IZN
130    DLK = (REAL(2*JN-1,JPKD)*DLX*DLKM1-REAL(JN-1,JPKD)*DLKM2)/REAL(JN,JPKD)
131    DLKM2 = DLKM1
132    DLKM1 = DLK
133  ENDDO
134  DLKM1 = DLKM2
135  DLLDN = (REAL(KN,JPKD)*(DLKM1-DLX*DLK))/(1.0_JPRB-DLX*DLX)
136  DLMOD = -DLK/DLLDN
137  DLXN = DLX+DLMOD
138  PXN = REAL(DLXN,JPKS)
139  DDXN = DLXN
140  PXMOD = REAL(DLMOD,JPKS)
141ENDIF
142!     ------------------------------------------------------------------
143
144!*         3.    Computes weight.
145!                ----------------
146
147
148IF(KFLAG == 1)THEN
149  DLKM2 = 1.0_JPRB
150  DLKM1 = DLXN
151  DLX = DLXN
152  DO JN=2,IZN
153    DLK = (REAL(2*JN-1,JPKD)*DLX*DLKM1-REAL(JN-1,JPKD)*DLKM2)/REAL(JN,JPKD)
154    DLKM2 = DLKM1
155    DLKM1 = DLK
156  ENDDO
157  DLKM1 = DLKM2
158  PW = REAL((1.0_JPRB-DLX*DLX)/(REAL(KN*KN,JPKD)*DLKM1*DLKM1),JPKS)
159ENDIF
160
161!     ------------------------------------------------------------------
162
163END SUBROUTINE CPLEDN
164END MODULE CPLEDN_MOD
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