1 | subroutine blowing_snow_sublim_sedim(ngrid,nlay,dtime,temp,q,qbs,pplay,paprs,dtemp_bs,dq_bs,dqbs_bs,bsfl,precip_bs) |
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2 | |
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3 | !============================================================================== |
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4 | ! Routine that calculates the evaporation and sedimentation of blowing snow |
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5 | ! inspired by what is done in lscp_mod |
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6 | ! Etienne Vignon, October 2022 |
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7 | !============================================================================== |
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8 | |
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9 | |
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10 | use blowing_snow_ini_mod, only : coef_eva_bs,RTT,RD,RG,expo_eva_bs, fallv_bs |
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11 | use blowing_snow_ini_mod, only : RCPD, RLSTT, RLMLT, RLVTT, RVTMP2 |
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12 | USE lmdz_lscp_tools, only : calc_qsat_ecmwf |
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13 | |
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14 | implicit none |
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15 | |
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16 | |
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17 | !++++++++++++++++++++++++++++++++++++++++++++++++++++ |
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18 | ! Declarations |
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19 | !++++++++++++++++++++++++++++++++++++++++++++++++++++ |
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20 | |
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21 | !INPUT |
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22 | !===== |
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23 | |
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24 | integer, intent(in) :: ngrid,nlay |
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25 | real, intent(in) :: dtime |
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26 | real, intent(in), dimension(ngrid,nlay) :: temp |
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27 | real, intent(in), dimension(ngrid,nlay) :: q |
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28 | real, intent(in), dimension(ngrid,nlay) :: qbs |
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29 | real, intent(in), dimension(ngrid,nlay) :: pplay |
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30 | real, intent(in), dimension(ngrid,nlay+1) :: paprs |
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31 | |
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32 | |
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33 | |
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34 | ! OUTPUT |
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35 | !======== |
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36 | |
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37 | |
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38 | real, intent(out), dimension(ngrid,nlay) :: dtemp_bs |
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39 | real, intent(out), dimension(ngrid,nlay) :: dq_bs |
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40 | real, intent(out), dimension(ngrid,nlay) :: dqbs_bs |
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41 | real, intent(out), dimension(ngrid,nlay+1) :: bsfl |
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42 | real, intent(out), dimension(ngrid) :: precip_bs |
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43 | |
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44 | |
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45 | ! LOCAL |
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46 | !====== |
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47 | |
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48 | |
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49 | integer :: k,i,n |
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50 | real :: zqev0, zqevi, zqevti, zcpair, zcpeau, dqbsmelt |
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51 | real :: dqsedim,precbs |
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52 | real, dimension(ngrid) :: zt,zq,zqbs,qsi,dqsi,qsl, dqsl,qzero,sedim,sedimn |
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53 | real, dimension(ngrid) :: zqbsi,zmqc, zmair, zdz |
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54 | real, dimension(ngrid,nlay) :: velo, zrho |
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55 | |
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56 | !++++++++++++++++++++++++++++++++++++++++++++++++++ |
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57 | ! Initialisation |
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58 | !++++++++++++++++++++++++++++++++++++++++++++++++++ |
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59 | |
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60 | qzero(:)=0. |
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61 | dtemp_bs(:,:)=0. |
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62 | dq_bs(:,:)=0. |
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63 | dqbs_bs(:,:)=0. |
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64 | velo(:,:)=0. |
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65 | zt(:)=0. |
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66 | zq(:)=0. |
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67 | zqbs(:)=0. |
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68 | sedim(:)=0. |
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69 | |
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70 | ! begin of top-down loop |
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71 | DO k = nlay, 1, -1 |
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72 | |
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73 | DO i=1,ngrid |
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74 | zt(i)=temp(i,k) |
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75 | zq(i)=q(i,k) |
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76 | zqbs(i)=qbs(i,k) |
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77 | ENDDO |
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78 | |
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79 | |
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80 | IF (k.LE.nlay-1) THEN |
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81 | |
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82 | ! thermalization of blowing snow precip coming from above |
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83 | DO i = 1, ngrid |
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84 | zmair(i)=(paprs(i,k)-paprs(i,k+1))/RG |
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85 | ! RVTMP2=rcpv/rcpd-1 |
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86 | zcpair=RCPD*(1.0+RVTMP2*zq(i)) |
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87 | zcpeau=RCPD*RVTMP2 |
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88 | ! zmqc: precipitation mass that has to be thermalized with |
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89 | ! layer's air so that precipitation at the ground has the |
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90 | ! same temperature as the lowermost layer |
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91 | zmqc(i) = (sedim(i))*dtime/zmair(i) |
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92 | ! t(i,k+1)+d_t(i,k+1): new temperature of the overlying layer |
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93 | zt(i) = ( (temp(i,k+1)+dtemp_bs(i,k+1))*zmqc(i)*zcpeau + zcpair*zt(i) ) & |
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94 | / (zcpair + zmqc(i)*zcpeau) |
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95 | ENDDO |
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96 | ELSE |
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97 | DO i = 1, ngrid |
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98 | zmair(i)=(paprs(i,k)-paprs(i,k+1))/RG |
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99 | zmqc(i) = 0. |
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100 | ENDDO |
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101 | |
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102 | ENDIF |
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103 | |
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104 | |
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105 | |
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106 | ! calulation saturation specific humidity |
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107 | CALL CALC_QSAT_ECMWF(ngrid,zt(:),qzero(:),pplay(:,k),RTT,2,.false.,qsi(:),dqsi(:)) |
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108 | CALL CALC_QSAT_ECMWF(ngrid,zt(:),qzero(:),pplay(:,k),RTT,1,.false.,qsl(:),dqsl(:)) |
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109 | ! sublimation calculation |
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110 | ! SUndqvist formula dP/dz=beta*(1-q/qsat)*sqrt(P) |
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111 | |
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112 | DO i = 1, ngrid |
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113 | ! if sedimentation: |
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114 | IF (sedim(i) .GT. 0.) THEN |
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115 | |
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116 | IF (zt(i) .GT. RTT) THEN |
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117 | ! if positive celcius temperature, we assume |
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118 | ! that all the blowing snow melt and evaporate |
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119 | zqevti=sedim(i)*(paprs(i,k)-paprs(i,k+1))/pplay(i,k)*zt(i)*RD/RG |
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120 | ! we ensure that the whole mesh does not exceed saturation wrt liquid |
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121 | zqev0 = MAX(0.0, qsl(i)-zq(i)) |
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122 | zqevi = MIN(zqev0,zqevti) |
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123 | ! New solid precipitation fluxes |
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124 | sedimn(i) = Max(0.,sedim(i) - zqevi*(paprs(i,k)-paprs(i,k+1))/RG/dtime) |
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125 | ! vapor, temperature, precip fluxes update |
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126 | zq(i) = zq(i) - (sedimn(i)-sedim(i))*(RG/(paprs(i,k)-paprs(i,k+1)))*dtime |
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127 | zq(i) = max(0., zq(i)) |
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128 | !zqbs(i) = zqbs(i) + (sedimn(i)-sedim(i)) * (RG/(paprs(i,k)-paprs(i,k+1)))*dtime |
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129 | !zqbs(i) = max(0., zqbs(i)) |
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130 | ! melting |
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131 | zt(i) = zt(i) & |
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132 | + (sedimn(i)-sedim(i)) & |
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133 | * (RG/(paprs(i,k)-paprs(i,k+1)))*dtime & |
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134 | * RLMLT/RCPD/(1.0+RVTMP2*(zq(i)+zqbs(i))) |
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135 | ! evaporation |
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136 | zt(i) = zt(i) & |
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137 | + (sedimn(i)-sedim(i)) & |
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138 | * (RG/(paprs(i,k)-paprs(i,k+1)))*dtime & |
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139 | * RLVTT/RCPD/(1.0+RVTMP2*(zq(i)+zqbs(i))) |
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140 | |
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141 | |
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142 | ELSE |
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143 | zqevti = coef_eva_bs*(1.0-zq(i)/qsi(i))*(sedim(i)**expo_eva_bs) & |
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144 | *(paprs(i,k)-paprs(i,k+1))/pplay(i,k)*zt(i)*RD/RG |
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145 | zqevti = MAX(0.0,MIN(zqevti,sedim(i)))*RG*dtime/(paprs(i,k)-paprs(i,k+1)) |
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146 | |
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147 | ! Sublimation limit: we ensure that the whole mesh does not exceed saturation wrt ice |
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148 | zqev0 = MAX(0.0, qsi(i)-zq(i)) |
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149 | zqevi = MIN(zqev0,zqevti) |
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150 | |
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151 | ! New solid precipitation fluxes |
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152 | sedimn(i) = Max(0.,sedim(i) - zqevi*(paprs(i,k)-paprs(i,k+1))/RG/dtime) |
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153 | |
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154 | |
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155 | ! vapor, temperature, precip fluxes update following sublimation |
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156 | zq(i) = zq(i) - (sedimn(i)-sedim(i))*(RG/(paprs(i,k)-paprs(i,k+1)))*dtime |
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157 | zq(i) = max(0., zq(i)) |
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158 | !zqbs(i) = zqbs(i) + (sedimn(i)-sedim(i)) * (RG/(paprs(i,k)-paprs(i,k+1)))*dtime |
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159 | !zqbs(i) = max(0., zqbs(i)) |
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160 | zt(i) = zt(i) & |
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161 | + (sedimn(i)-sedim(i)) & |
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162 | * (RG/(paprs(i,k)-paprs(i,k+1)))*dtime & |
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163 | * RLSTT/RCPD/(1.0+RVTMP2*(zq(i)+zqbs(i))) |
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164 | ENDIF |
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165 | |
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166 | |
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167 | ! sedim update |
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168 | sedim(i)=sedimn(i) |
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169 | |
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170 | |
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171 | ELSE |
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172 | sedim(i)=0. |
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173 | ENDIF ! if sedim > 0 |
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174 | |
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175 | zqbsi(i)=zqbs(i) |
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176 | |
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177 | ENDDO ! loop on ngrid |
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178 | |
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179 | ! Now sedimention scheme |
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180 | |
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181 | ! exact resolution of the conservation equation for qbs with the updated flux from the top (after evap) |
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182 | ! valid only if the fall velocity is constant |
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183 | |
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184 | DO i = 1, ngrid |
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185 | |
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186 | zrho(i,k) = pplay(i,k) / zt(i) / RD |
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187 | zdz(i) = (paprs(i,k)-paprs(i,k+1)) / (zrho(i,k)*RG) |
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188 | velo(i,k) = fallv_bs |
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189 | zqbs(i) = zqbsi(i)*exp(-velo(i,k)/zdz(i)*dtime)+sedim(i)/zrho(i,k)/velo(i,k) |
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190 | zqbs(i) = max(zqbs(i),0.) |
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191 | ! flux update |
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192 | sedim(i) = sedim(i) + zrho(i,k)*zdz(i)/dtime*(zqbsi(i)-zqbs(i)) |
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193 | sedim(i) = max(0.,sedim(i)) |
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194 | |
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195 | ENDDO |
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196 | |
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197 | ! old version with bugs |
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198 | ! DO n = 1, niter_bs |
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199 | ! DO i = 1, ngrid |
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200 | ! zrho(i,k) = pplay(i,k) / zt(i) / RD |
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201 | ! zdz(i) = (paprs(i,k)-paprs(i,k+1)) / (zrho(i,k)*RG) |
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202 | ! velo(i,k) = fallv_bs |
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203 | ! dqsedim = dtime/REAL(niter_bs)/zdz(i)*zqbs(i)*velo(i,k) ! dqice/dt=1/rho*d(rho*wice*qice)/dz |
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204 | ! precbs = MIN(MAX(dqsedim,0.0),zqbs(i)) |
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205 | ! zqbs(i) = MAX(zqbs(i)-1.*precbs , 0.0) |
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206 | ! ENDDO !loop on ngrid |
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207 | ! ENDDO ! loop on niter_bs |
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208 | ! ! add to non sublimated precip |
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209 | ! DO i=1,ngrid |
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210 | ! sedim(i) = sedim(i)+max(0.,zqbsi(i)-zqbs(i))*(paprs(i,k)-paprs(i,k+1))/(RG*dtime) |
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211 | ! ENDDO |
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212 | ! |
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213 | |
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214 | |
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215 | |
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216 | ! Outputs: |
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217 | DO i = 1, ngrid |
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218 | bsfl(i,k)=sedim(i) |
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219 | dqbs_bs(i,k) = zqbs(i)-qbs(i,k) |
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220 | dq_bs(i,k) = zq(i) - q(i,k) |
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221 | dtemp_bs(i,k) = zt(i) - temp(i,k) |
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222 | ENDDO |
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223 | |
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224 | |
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225 | ENDDO ! vertical loop |
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226 | |
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227 | |
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228 | !surface bs flux |
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229 | DO i = 1, ngrid |
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230 | precip_bs(i) = sedim(i) |
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231 | ENDDO |
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232 | |
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233 | |
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234 | return |
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235 | |
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236 | end subroutine blowing_snow_sublim_sedim |
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