1 | SUBROUTINE FLOTT_GWD_RAN(NLON,NLEV,DTIME, pp, pn2, & |
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2 | tt,uu,vv,zustr,zvstr,d_t, d_u, d_v) |
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3 | |
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4 | !---------------------------------------------------------------------- |
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5 | ! Parametrization of the momentum flux deposition due to a discrete |
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6 | ! number of gravity waves. |
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7 | ! F. Lott (version 9: 16 February, 2012), reproduce v3 but with only |
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8 | ! two waves present at each time step |
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9 | ! LMDz model online version |
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10 | ! ADAPTED FOR VENUS |
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11 | !--------------------------------------------------------------------- |
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12 | |
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13 | use dimphy |
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14 | implicit none |
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15 | |
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16 | #include "dimensions.h" |
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17 | #include "paramet.h" |
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18 | |
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19 | #include "YOEGWD.h" |
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20 | #include "YOMCST.h" |
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21 | |
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22 | ! 0. DECLARATIONS: |
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23 | |
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24 | ! 0.1 INPUTS |
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25 | INTEGER, intent(in):: NLON, NLEV |
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26 | REAL, intent(in):: DTIME ! Time step of the Physics |
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27 | REAL, intent(in):: pp(NLON, NLEV) ! Pressure at full levels |
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28 | ! VENUS ATTENTION: CP VARIABLE PN2 CALCULE EN AMONT DES PARAMETRISATIONS |
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29 | REAL, intent(in):: pn2(NLON,NLEV) ! N2 (BV^2) at 1/2 levels |
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30 | REAL, intent(in):: TT(NLON, NLEV) ! Temp at full levels |
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31 | |
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32 | REAL, intent(in):: UU(NLON, NLEV) , VV(NLON, NLEV) |
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33 | ! Hor winds at full levels |
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34 | |
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35 | ! 0.2 OUTPUTS |
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36 | REAL, intent(out):: zustr(NLON), zvstr(NLON) ! Surface Stresses |
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37 | REAL, intent(inout):: d_t(NLON, NLEV) ! Tendency on Temp. |
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38 | |
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39 | REAL, intent(inout):: d_u(NLON, NLEV), d_v(NLON, NLEV) |
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40 | ! Tendencies on winds |
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41 | |
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42 | ! O.3 INTERNAL ARRAYS |
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43 | |
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44 | INTEGER II, LL, IEQ |
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45 | |
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46 | ! 0.3.0 TIME SCALE OF THE LIFE CYCLE OF THE WAVES PARAMETERIZED |
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47 | |
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48 | REAL DELTAT |
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49 | |
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50 | ! 0.3.1 GRAVITY-WAVES SPECIFICATIONS |
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51 | |
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52 | !VENUS |
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53 | INTEGER, PARAMETER:: NK = 2, NP = 2, NO = 2, NW = NK * NP * NO |
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54 | !Online output: change NO |
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55 | ! INTEGER, PARAMETER:: NK = 1, NP = 2, NO = 11, NW = NK * NP * NO |
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56 | INTEGER JK, JP, JO, JW |
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57 | REAL KMIN, KMAX ! Min and Max horizontal wavenumbers |
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58 | REAL CMIN, CMAX ! Min and Max absolute ph. vel. |
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59 | REAL CPHA ! absolute PHASE VELOCITY frequency |
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60 | REAL ZK(NW, KLON) ! Horizontal wavenumber amplitude |
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61 | REAL ZP(NW) ! Horizontal wavenumber angle |
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62 | REAL ZO(NW, KLON) ! Absolute frequency ! |
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63 | |
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64 | ! Waves Intr. freq. at the 1/2 lev surrounding the full level |
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65 | REAL ZOM(NW, KLON), ZOP(NW, KLON) |
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66 | |
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67 | ! Wave vertical velocities at the 2 1/2 lev surrounding the full level |
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68 | REAL WWM(NW, KLON), WWP(NW, KLON) |
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69 | |
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70 | REAL RUW0(NW, KLON) ! Fluxes at launching level |
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71 | |
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72 | REAL RUWP(NW, KLON), RVWP(NW, KLON) |
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73 | ! Fluxes X and Y for each waves at 1/2 Levels |
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74 | |
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75 | INTEGER LAUNCH ! Launching altitude |
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76 | |
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77 | REAL RUWMAX,SAT ! saturation parameter |
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78 | REAL XLAUNCH ! Controle the launching altitude |
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79 | REAL RUW(KLON, KLEV + 1) ! Flux x at semi levels |
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80 | REAL RVW(KLON, KLEV + 1) ! Flux y at semi levels |
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81 | |
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82 | ! 0.3.2 PARAMETERS OF WAVES DISSIPATIONS |
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83 | |
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84 | REAL RDISS, ZOISEC ! COEFF DE DISSIPATION, SECURITY FOR INTRINSIC FREQ |
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85 | |
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86 | ! 0.3.3 BACKGROUND FLOW AT 1/2 LEVELS AND VERTICAL COORDINATE |
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87 | |
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88 | REAL H0bis(KLON, KLEV) ! Characteristic Height of the atmosphere |
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89 | REAL H0 ! Characteristic Height of the atmosphere |
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90 | REAL PR, TR ! Reference Pressure and Temperature |
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91 | |
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92 | REAL ZH(KLON, KLEV + 1) ! Log-pressure altitude (constant H0) |
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93 | REAL ZHbis(KLON, KLEV + 1) ! Log-pressure altitude (varying H) |
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94 | |
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95 | REAL UH(KLON, KLEV + 1), VH(KLON, KLEV + 1) ! Winds at 1/2 levels |
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96 | REAL PH(KLON, KLEV + 1) ! Pressure at 1/2 levels |
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97 | REAL PSEC ! Security to avoid division by 0 pressure |
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98 | REAL BV(KLON, KLEV + 1) ! Brunt Vaisala freq. (BVF) at 1/2 levels |
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99 | REAL BVSEC ! Security to avoid negative BVF |
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100 | |
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101 | ! COSMETICS TO DIAGNOSE EACH WAVES CONTRIBUTION. |
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102 | logical output |
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103 | data output/.false./ |
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104 | ! CAUTION ! IF output is .true. THEN change NO to 10 at least ! |
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105 | character*14 outform |
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106 | character*2 str2 |
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107 | |
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108 | ! ON CONSERVE LA MEMOIRE un certain temps AVEC UN SAVE |
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109 | real,save,allocatable :: d_u_sav(:,:),d_v_sav(:,:) |
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110 | LOGICAL firstcall |
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111 | SAVE firstcall |
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112 | DATA firstcall/.true./ |
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113 | |
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114 | REAL ALEAS |
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115 | EXTERNAL ALEAS |
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116 | |
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117 | !----------------------------------------------------------------- |
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118 | ! 1. INITIALISATIONS |
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119 | |
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120 | IF (firstcall) THEN |
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121 | allocate(d_u_sav(NLON,NLEV),d_v_sav(NLON,NLEV)) |
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122 | d_u_sav = 0. |
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123 | d_v_sav = 0. |
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124 | firstcall=.false. |
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125 | ENDIF |
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126 | |
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127 | ! 1.1 Basic parameter |
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128 | |
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129 | ! PARAMETERS CORRESPONDING TO V3: |
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130 | RUWMAX = 0.005 ! Max EP-Flux at Launch altitude |
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131 | SAT = 0.85 ! Saturation parameter: Sc in (12) |
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132 | RDISS = 10. ! Diffusion parameter |
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133 | |
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134 | DELTAT=24.*3600. ! Time scale of the waves (first introduced in 9b) |
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135 | |
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136 | KMIN = 1.E-6 ! Min horizontal wavenumber |
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137 | KMAX = 2.E-5 ! Max horizontal wavenumber |
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138 | !Online output: one value only |
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139 | if (output) then |
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140 | KMIN = 6.3E-6 |
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141 | KMAX = 6.3E-6 |
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142 | endif |
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143 | CMIN = 1. ! Min phase velocity |
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144 | CMAX = 61. ! Max phase speed velocity |
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145 | XLAUNCH=0.6 ! Parameter that control launching altitude |
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146 | |
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147 | PR = 9.2e6 ! Reference pressure ! VENUS!! |
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148 | TR = 240. ! Reference Temperature ! VENUS: cloud layer |
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149 | H0 = RD * TR / RG ! Characteristic vertical scale height |
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150 | |
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151 | BVSEC = 1.E-5 ! Security to avoid negative BVF |
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152 | PSEC = 1.E-8 ! Security to avoid division by 0 pressure |
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153 | ZOISEC = 1.E-8 ! Security FOR 0 INTRINSIC FREQ |
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154 | |
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155 | IF(DELTAT.LT.DTIME)THEN |
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156 | PRINT *,'GWD RANDO: DELTAT LT DTIME!' |
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157 | STOP |
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158 | ENDIF |
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159 | |
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160 | |
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161 | IF (NLEV < NW) THEN |
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162 | PRINT *, 'YOU WILL HAVE PROBLEM WITH RANDOM NUMBERS' |
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163 | PRINT *, 'FLOTT GWD STOP' |
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164 | STOP 1 |
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165 | ENDIF |
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166 | |
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167 | ! 1.2 WAVES CHARACTERISTICS CHOSEN RANDOMLY |
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168 | !------------------------------------------- |
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169 | |
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170 | ! The mod function of here a weird arguments |
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171 | ! are used to produce the waves characteristics |
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172 | ! in a stochastic way |
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173 | |
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174 | JW = 0 |
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175 | DO JP = 1, NP |
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176 | DO JK = 1, NK |
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177 | DO JO = 1, NO |
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178 | JW = JW + 1 |
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179 | ! Angle |
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180 | ZP(JW) = 2. * RPI * REAL(JP - 1) / REAL(NP) |
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181 | DO II = 1, KLON |
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182 | ! Horizontal wavenumber amplitude |
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183 | ! ZK(JW, II) = KMIN + (KMAX - KMIN) * MOD(TT(II, JW) * 100., 1.) |
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184 | ZK(JW, II) = KMIN + (KMAX - KMIN) * ALEAS(0.) |
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185 | ! Horizontal phase speed |
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186 | ! CPHA = CMIN + (CMAX - CMIN) * MOD(TT(II, JW)**2, 1.) |
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187 | CPHA = CMIN + (CMAX - CMIN) * ALEAS(0.) |
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188 | !Online output: linear |
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189 | if (output) CPHA = CMIN + (CMAX - CMIN) * (JO-1)/(NO-1) |
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190 | ! Intrinsic frequency |
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191 | ZO(JW, II) = CPHA * ZK(JW, II) |
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192 | ! Momentum flux at launch lev |
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193 | ! RUW0(JW, II) = RUWMAX / REAL(NW) & |
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194 | RUW0(JW, II) = RUWMAX & |
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195 | ! * MOD(100. * (UU(II, JW)**2 + VV(II, JW)**2), 1.) |
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196 | * ALEAS(0.) |
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197 | !Online output: fixed to max |
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198 | if (output) RUW0(JW, II) = RUWMAX |
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199 | ENDDO |
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200 | end DO |
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201 | end DO |
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202 | end DO |
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203 | |
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204 | ! 2. EVALUATION OF THE BACKGROUND FLOW AT SEMI-LEVELS |
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205 | !------------------------------------------------------------- |
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206 | |
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207 | IEQ = KLON / 2 |
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208 | !Online output |
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209 | if (output) OPEN(11,file="impact-gwno.dat") |
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210 | |
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211 | ! Pressure and Inv of pressure, Temperature / at 1/2 level |
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212 | DO LL = 2, KLEV |
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213 | PH(:, LL) = EXP((LOG(PP(:, LL)) + LOG(PP(:, LL - 1))) / 2.) |
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214 | end DO |
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215 | |
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216 | PH(:, KLEV + 1) = 0. |
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217 | PH(:, 1) = 2. * PP(:, 1) - PH(:, 2) |
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218 | |
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219 | ! Launching altitude |
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220 | |
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221 | DO LL = 1, NLEV |
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222 | IF (PH(IEQ, LL) / PH(IEQ, 1) > XLAUNCH) LAUNCH = LL |
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223 | ENDDO |
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224 | |
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225 | ! Log pressure vert. coordinate (altitude above surface) |
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226 | ZHbis(:,1) = 0. |
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227 | DO LL = 2, KLEV + 1 |
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228 | H0bis(:, LL-1) = RD * TT(:, LL-1) / RG |
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229 | ZHbis(:, LL) = ZHbis(:, LL-1) & |
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230 | + H0bis(:, LL-1)*(PH(:, LL-1)-PH(:,LL))/PP(:, LL-1) |
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231 | end DO |
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232 | ! Log pressure vert. coordinate |
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233 | DO LL = 1, KLEV + 1 |
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234 | ZH(:, LL) = H0 * LOG(PR / (PH(:, LL) + PSEC)) |
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235 | end DO |
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236 | |
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237 | |
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238 | ! Winds and BV frequency |
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239 | DO LL = 2, KLEV |
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240 | UH(:, LL) = 0.5 * (UU(:, LL) + UU(:, LL - 1)) ! Zonal wind |
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241 | VH(:, LL) = 0.5 * (VV(:, LL) + VV(:, LL - 1)) ! Meridional wind |
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242 | ! BVSEC: BV Frequency |
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243 | ! VENUS ATTENTION: CP VARIABLE PSTAB CALCULE EN AMONT DES PARAMETRISATIONS |
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244 | BV(:, LL) = MAX(BVSEC,SQRT(pn2(:,LL))) |
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245 | end DO |
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246 | BV(:, 1) = BV(:, 2) |
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247 | UH(:, 1) = 0. |
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248 | VH(:, 1) = 0. |
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249 | BV(:, KLEV + 1) = BV(:, KLEV) |
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250 | UH(:, KLEV + 1) = UU(:, KLEV) |
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251 | VH(:, KLEV + 1) = VV(:, KLEV) |
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252 | |
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253 | |
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254 | ! 3. COMPUTE THE FLUXES |
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255 | !-------------------------- |
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256 | |
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257 | ! 3.1 Vertical velocity at launching altitude to ensure |
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258 | ! the correct value to the imposed fluxes. |
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259 | ! |
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260 | DO JW = 1, NW |
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261 | |
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262 | ! Evaluate intrinsic frequency at launching altitude: |
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263 | ZOP(JW, :) = ZO(JW, :) & |
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264 | - ZK(JW, :) * COS(ZP(JW)) * UH(:, LAUNCH) & |
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265 | - ZK(JW, :) * SIN(ZP(JW)) * VH(:, LAUNCH) |
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266 | ! Vertical velocity at launch level, value to ensure the imposed |
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267 | ! mom flux: |
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268 | WWP(JW, :) = SQRT(ABS(ZOP(JW, :)) / MAX(BV(:, LAUNCH),BVSEC) & |
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269 | * RUW0(JW,:)) |
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270 | RUWP(JW, :) = COS(ZP(JW)) * SIGN(1., ZOP(JW, :)) * RUW0(JW, :) |
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271 | RVWP(JW, :) = SIN(ZP(JW)) * SIGN(1., ZOP(JW, :)) * RUW0(JW, :) |
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272 | |
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273 | end DO |
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274 | |
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275 | ! 3.2 Uniform values below the launching altitude |
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276 | |
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277 | DO LL = 1, LAUNCH |
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278 | RUW(:, LL) = 0 |
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279 | RVW(:, LL) = 0 |
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280 | DO JW = 1, NW |
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281 | RUW(:, LL) = RUW(:, LL) + RUWP(JW, :) |
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282 | RVW(:, LL) = RVW(:, LL) + RVWP(JW, :) |
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283 | end DO |
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284 | end DO |
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285 | |
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286 | ! 3.3 Loop over altitudes, with passage from one level to the |
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287 | ! next done by i) conserving the EP flux, ii) dissipating |
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288 | ! a little, iii) testing critical levels, and vi) testing |
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289 | ! the breaking. |
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290 | |
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291 | !Online output |
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292 | write(str2,'(i2)') NW+2 |
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293 | outform="("//str2//"(E12.4,1X))" |
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294 | if (output) WRITE(11,outform) ZH(IEQ, 1) / 1000., ZHbis(IEQ, 1) / 1000., & |
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295 | (ZO(JW, IEQ)/ZK(JW, IEQ)*COS(ZP(JW)), JW = 1, NW) |
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296 | |
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297 | DO LL = LAUNCH, KLEV - 1 |
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298 | |
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299 | |
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300 | ! W(KB)ARNING: ALL THE PHYSICS IS HERE (PASSAGE FROM ONE LEVEL |
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301 | ! TO THE NEXT) |
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302 | DO JW = 1, NW |
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303 | ZOM(JW, :) = ZOP(JW, :) |
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304 | WWM(JW, :) = WWP(JW, :) |
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305 | ! Intrinsic Frequency |
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306 | ZOP(JW, :) = ZO(JW, :) - ZK(JW, :) * COS(ZP(JW)) * UH(:, LL + 1) & |
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307 | - ZK(JW, :) * SIN(ZP(JW)) * VH(:, LL + 1) |
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308 | |
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309 | WWP(JW, :) = MIN( & |
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310 | ! No breaking (Eq.6) |
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311 | WWM(JW, :) & |
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312 | * SQRT(BV(:, LL ) / BV(:, LL+1) & |
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313 | * ABS(ZOP(JW, :)) / MAX(ABS(ZOM(JW, :)), ZOISEC)) & |
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314 | ! Dissipation (Eq. 8): |
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315 | * EXP(- RDISS * PR / (PH(:, LL + 1) + PH(:, LL)) & |
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316 | * ((BV(:, LL + 1) + BV(:, LL)) / 2.)**3 & |
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317 | / MAX(ABS(ZOP(JW, :) + ZOM(JW, :)) / 2., ZOISEC)**4 & |
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318 | * ZK(JW, :)**3 * (ZH(:, LL + 1) - ZH(:, LL))), & |
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319 | ! Critical levels (forced to zero if intrinsic |
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320 | ! frequency changes sign) |
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321 | MAX(0., SIGN(1., ZOP(JW, :) * ZOM(JW, :))) & |
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322 | ! Saturation (Eq. 12) |
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323 | * ZOP(JW, :)**2 / ZK(JW, :)/BV(:, LL+1) & |
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324 | * EXP(-ZH(:, LL + 1)/2./H0) * SAT) |
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325 | end DO |
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326 | |
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327 | ! END OF W(KB)ARNING |
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328 | ! Evaluate EP-flux from Eq. 7 and |
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329 | ! Give the right orientation to the stress |
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330 | |
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331 | DO JW = 1, NW |
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332 | RUWP(JW, :) = ZOP(JW, :)/MAX(ABS(ZOP(JW, :)), ZOISEC)**2 & |
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333 | *BV(:,LL+1)& |
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334 | * COS(ZP(JW)) * WWP(JW, :)**2 |
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335 | RVWP(JW, :) = ZOP(JW, :)/MAX(ABS(ZOP(JW, :)), ZOISEC)**2 & |
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336 | *BV(:,LL+1)& |
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337 | * SIN(ZP(JW)) * WWP(JW, :)**2 |
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338 | end DO |
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339 | ! |
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340 | RUW(:, LL + 1) = 0. |
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341 | RVW(:, LL + 1) = 0. |
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342 | |
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343 | DO JW = 1, NW |
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344 | RUW(:, LL + 1) = RUW(:, LL + 1) + RUWP(JW, :) |
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345 | RVW(:, LL + 1) = RVW(:, LL + 1) + RVWP(JW, :) |
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346 | end DO |
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347 | !Online output |
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348 | if (output) then |
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349 | do JW=1,NW |
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350 | if(RUWP(JW, IEQ).gt.0.) then |
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351 | RUWP(JW, IEQ) = max(RUWP(JW, IEQ), 1.e-99) |
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352 | else |
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353 | RUWP(JW, IEQ) = min(RUWP(JW, IEQ), -1.e-99) |
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354 | endif |
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355 | enddo |
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356 | WRITE(11,outform) ZH(IEQ, LL+1) / 1000., & |
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357 | ZHbis(IEQ, LL+1) / 1000., & |
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358 | (RUWP(JW, IEQ), JW = 1, NW) |
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359 | endif |
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360 | |
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361 | end DO |
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362 | |
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363 | !Online output |
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364 | if (output) then |
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365 | CLOSE(11) |
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366 | stop |
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367 | endif |
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368 | |
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369 | ! 4 CALCUL DES TENDANCES: |
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370 | !------------------------ |
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371 | |
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372 | ! 4.1 Rectification des flux au sommet et dans les basses couches: |
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373 | |
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374 | RUW(:, KLEV + 1) = 0. |
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375 | RVW(:, KLEV + 1) = 0. |
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376 | RUW(:, 1) = RUW(:, LAUNCH) |
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377 | RVW(:, 1) = RVW(:, LAUNCH) |
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378 | DO LL = 2, LAUNCH |
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379 | RUW(:, LL) = RUW(:, LL - 1) + (RUW(:, LAUNCH + 1) - RUW(:, 1)) * & |
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380 | (PH(:, LL) - PH(:, LL - 1)) / (PH(:, LAUNCH + 1) - PH(:, 1)) |
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381 | RVW(:, LL) = RVW(:, LL - 1) + (RVW(:, LAUNCH + 1) - RVW(:, 1)) * & |
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382 | (PH(:, LL) - PH(:, LL - 1)) / (PH(:, LAUNCH + 1) - PH(:, 1)) |
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383 | end DO |
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384 | |
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385 | ! AR-1 RECURSIVE FORMULA (13) IN VERSION 4 |
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386 | DO LL = 1, KLEV |
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387 | d_u(:, LL) = RG * (RUW(:, LL + 1) - RUW(:, LL)) & |
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388 | / (PH(:, LL + 1) - PH(:, LL)) * DTIME |
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389 | d_v(:, LL) = RG * (RVW(:, LL + 1) - RVW(:, LL)) & |
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390 | / (PH(:, LL + 1) - PH(:, LL)) * DTIME |
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391 | ENDDO |
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392 | d_t = 0. |
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393 | ! ON CONSERVE LA MEMOIRE un certain temps AVEC UN SAVE |
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394 | d_u = DTIME/DELTAT/REAL(NW) * d_u + (1.-DTIME/DELTAT) * d_u_sav |
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395 | d_v = DTIME/DELTAT/REAL(NW) * d_v + (1.-DTIME/DELTAT) * d_v_sav |
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396 | d_u_sav = d_u |
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397 | d_v_sav = d_v |
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398 | |
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399 | ! Cosmetic: evaluation of the cumulated stress |
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400 | |
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401 | ZUSTR(:) = 0. |
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402 | ZVSTR(:) = 0. |
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403 | DO LL = 1, KLEV |
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404 | ZUSTR(:) = ZUSTR(:) + D_U(:, LL) / RG * (PH(:, LL + 1) - PH(:, LL)) |
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405 | ZVSTR(:) = ZVSTR(:) + D_V(:, LL) / RG * (PH(:, LL + 1) - PH(:, LL)) |
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406 | ENDDO |
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407 | |
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408 | END SUBROUTINE FLOTT_GWD_RAN |
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409 | |
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410 | !=================================================================== |
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411 | !=================================================================== |
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412 | !=================================================================== |
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413 | !=================================================================== |
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414 | |
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415 | FUNCTION ALEAS (R) |
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416 | !***BEGIN PROLOGUE ALEAS |
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417 | !***PURPOSE Generate a uniformly distributed random number. |
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418 | !***LIBRARY SLATEC (FNLIB) |
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419 | !***CATEGORY L6A21 |
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420 | !***TYPE SINGLE PRECISION (ALEAS-S) |
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421 | !***KEYWORDS FNLIB, ALEAS NUMBER, SPECIAL FUNCTIONS, UNIFORM |
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422 | !***AUTHOR Fullerton, W., (LANL) |
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423 | !***DESCRIPTION |
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424 | ! |
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425 | ! This pseudo-random number generator is portable among a wide |
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426 | ! variety of computers. RAND(R) undoubtedly is not as good as many |
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427 | ! readily available installation dependent versions, and so this |
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428 | ! routine is not recommended for widespread usage. Its redeeming |
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429 | ! feature is that the exact same random numbers (to within final round- |
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430 | ! off error) can be generated from machine to machine. Thus, programs |
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431 | ! that make use of random numbers can be easily transported to and |
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432 | ! checked in a new environment. |
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433 | ! |
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434 | ! The random numbers are generated by the linear congruential |
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435 | ! method described, e.g., by Knuth in Seminumerical Methods (p.9), |
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436 | ! Addison-Wesley, 1969. Given the I-th number of a pseudo-random |
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437 | ! sequence, the I+1 -st number is generated from |
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438 | ! X(I+1) = (A*X(I) + C) MOD M, |
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439 | ! where here M = 2**22 = 4194304, C = 1731 and several suitable values |
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440 | ! of the multiplier A are discussed below. Both the multiplier A and |
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441 | ! random number X are represented in double precision as two 11-bit |
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442 | ! words. The constants are chosen so that the period is the maximum |
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443 | ! possible, 4194304. |
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444 | ! |
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445 | ! In order that the same numbers be generated from machine to |
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446 | ! machine, it is necessary that 23-bit integers be reducible modulo |
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447 | ! 2**11 exactly, that 23-bit integers be added exactly, and that 11-bit |
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448 | ! integers be multiplied exactly. Furthermore, if the restart option |
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449 | ! is used (where R is between 0 and 1), then the product R*2**22 = |
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450 | ! R*4194304 must be correct to the nearest integer. |
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451 | ! |
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452 | ! The first four random numbers should be .0004127026, |
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453 | ! .6750836372, .1614754200, and .9086198807. The tenth random number |
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454 | ! is .5527787209, and the hundredth is .3600893021 . The thousandth |
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455 | ! number should be .2176990509 . |
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456 | ! |
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457 | ! In order to generate several effectively independent sequences |
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458 | ! with the same generator, it is necessary to know the random number |
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459 | ! for several widely spaced calls. The I-th random number times 2**22, |
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460 | ! where I=K*P/8 and P is the period of the sequence (P = 2**22), is |
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461 | ! still of the form L*P/8. In particular we find the I-th random |
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462 | ! number multiplied by 2**22 is given by |
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463 | ! I = 0 1*P/8 2*P/8 3*P/8 4*P/8 5*P/8 6*P/8 7*P/8 8*P/8 |
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464 | ! RAND= 0 5*P/8 2*P/8 7*P/8 4*P/8 1*P/8 6*P/8 3*P/8 0 |
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465 | ! Thus the 4*P/8 = 2097152 random number is 2097152/2**22. |
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466 | ! |
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467 | ! Several multipliers have been subjected to the spectral test |
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468 | ! (see Knuth, p. 82). Four suitable multipliers roughly in order of |
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469 | ! goodness according to the spectral test are |
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470 | ! 3146757 = 1536*2048 + 1029 = 2**21 + 2**20 + 2**10 + 5 |
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471 | ! 2098181 = 1024*2048 + 1029 = 2**21 + 2**10 + 5 |
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472 | ! 3146245 = 1536*2048 + 517 = 2**21 + 2**20 + 2**9 + 5 |
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473 | ! 2776669 = 1355*2048 + 1629 = 5**9 + 7**7 + 1 |
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474 | ! |
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475 | ! In the table below LOG10(NU(I)) gives roughly the number of |
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476 | ! random decimal digits in the random numbers considered I at a time. |
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477 | ! C is the primary measure of goodness. In both cases bigger is better. |
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478 | ! |
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479 | ! LOG10 NU(I) C(I) |
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480 | ! A I=2 I=3 I=4 I=5 I=2 I=3 I=4 I=5 |
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481 | ! |
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482 | ! 3146757 3.3 2.0 1.6 1.3 3.1 1.3 4.6 2.6 |
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483 | ! 2098181 3.3 2.0 1.6 1.2 3.2 1.3 4.6 1.7 |
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484 | ! 3146245 3.3 2.2 1.5 1.1 3.2 4.2 1.1 0.4 |
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485 | ! 2776669 3.3 2.1 1.6 1.3 2.5 2.0 1.9 2.6 |
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486 | ! Best |
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487 | ! Possible 3.3 2.3 1.7 1.4 3.6 5.9 9.7 14.9 |
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488 | ! |
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489 | ! Input Argument -- |
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490 | ! R If R=0., the next random number of the sequence is generated. |
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491 | ! If R .LT. 0., the last generated number will be returned for |
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492 | ! possible use in a restart procedure. |
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493 | ! If R .GT. 0., the sequence of random numbers will start with |
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494 | ! the seed R mod 1. This seed is also returned as the value of |
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495 | ! RAND provided the arithmetic is done exactly. |
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496 | ! |
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497 | ! Output Value -- |
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498 | ! RAND a pseudo-random number between 0. and 1. |
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499 | ! |
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500 | !***REFERENCES (NONE) |
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501 | !***ROUTINES CALLED (NONE) |
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502 | !***REVISION HISTORY (YYMMDD) |
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503 | ! 770401 DATE WRITTEN |
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504 | ! 890531 Changed all specific intrinsics to generic. (WRB) |
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505 | ! 890531 REVISION DATE from Version 3.2 |
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506 | ! 891214 Prologue converted to Version 4.0 format. (BAB) |
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507 | !***END PROLOGUE RAND |
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508 | SAVE IA1, IA0, IA1MA0, IC, IX1, IX0 |
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509 | DATA IA1, IA0, IA1MA0 /1536, 1029, 507/ |
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510 | DATA IC /1731/ |
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511 | DATA IX1, IX0 /0, 0/ |
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512 | !***FIRST EXECUTABLE STATEMENT RAND |
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513 | ! |
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514 | ! A*X = 2**22*IA1*IX1 + 2**11*(IA1*IX1 + (IA1-IA0)*(IX0-IX1) |
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515 | ! + IA0*IX0) + IA0*IX0 |
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516 | ! |
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517 | IF (R.EQ.0.) THEN |
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518 | IY0 = IA0*IX0 |
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519 | IY1 = IA1*IX1 + IA1MA0*(IX0-IX1) + IY0 |
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520 | IY0 = IY0 + IC |
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521 | IX0 = MOD (IY0, 2048) |
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522 | IY1 = IY1 + (IY0-IX0)/2048 |
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523 | IX1 = MOD (IY1, 2048) |
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524 | ENDIF |
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525 | |
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526 | IF (R.GT.0.) THEN |
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527 | IX1 = MOD(R,1.)*4194304. + 0.5 |
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528 | IX0 = MOD (IX1, 2048) |
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529 | IX1 = (IX1-IX0)/2048 |
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530 | ENDIF |
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531 | |
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532 | ALEAS = IX1*2048 + IX0 |
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533 | ALEAS = ALEAS / 4194304. |
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534 | RETURN |
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535 | |
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536 | END |
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537 | |
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538 | |
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