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SURFEX v7.3
General documentation of Surfex
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SURFEX v7.3
General documentation of Surfex
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00001 ! ######### 00002 SUBROUTINE HYDRO_SNOW( OGLACIER, PTSTEP, PVEGTYPE, & 00003 PSR, PLES, PMELT, & 00004 PSNOWSWE, PSNOWALB, PSNOWRHO, PPG_MELT ) 00005 ! ##################################################################### 00006 ! 00007 !!**** *HYDRO_SNOW* 00008 !! 00009 !! PURPOSE 00010 !! ------- 00011 ! 00012 ! Calculates i) Snow water transfer to soil for both snow scheme options. 00013 ! ii) the evolution of the snowpack using the Force-Restore 00014 ! option of Douville et al. (1995): 'DEF' 00015 ! Calculate the snow cover liquid water equivalent (Ws), the albedo and density of 00016 ! the snow (i.e., SNOWALB and SNOWRHO). Also determine the runoff and drainage 00017 ! into the soil. 00018 ! 00019 ! 00020 !!** METHOD 00021 !! ------ 00022 ! 00023 !! EXTERNAL 00024 !! -------- 00025 !!REAL, DIMENSION(:), INTENT(INOUT) :: PTG 00026 ! PTG = surface temperature at 't' 00027 00028 !! none 00029 !! 00030 !! IMPLICIT ARGUMENTS 00031 !! ------------------ 00032 !! 00033 !! 00034 !! 00035 !! REFERENCE 00036 !! --------- 00037 !! 00038 !! Noilhan and Planton (1989) 00039 !! Belair (1995) 00040 !! 00041 !! AUTHOR 00042 !! ------ 00043 !! 00044 !! S. Belair * Meteo-France * 00045 !! 00046 !! MODIFICATIONS 00047 !! ------------- 00048 !! 00049 !! Original 14/03/95 00050 !! 31/08/98 (V. Masson and F. Habets) add Dumenil et Todini 00051 !! runoff scheme 00052 !! 31/08/98 (V. Masson and A. Boone) add the third soil-water 00053 !! reservoir (WG3,D3) 00054 !! 14/05/02 (A. Boone) snow only, and skip code if '3-L' option in force 00055 !! 03/2009 (B. Decharme) Consistency with Arpege permanent snow/ice treatment 00056 !! (LGLACIER) 00057 !------------------------------------------------------------------------------- 00058 ! 00059 !* 0. DECLARATIONS 00060 ! ------------ 00061 ! 00062 USE MODD_CSTS, ONLY : XLSTT, XLMTT, XDAY 00063 USE MODD_SNOW_PAR, ONLY : XANS_T, XANS_TODRY, XANSMIN, XANSMAX, & 00064 XRHOSMAX, XRHOSMIN, XWCRN, XAGLAMIN, & 00065 XAGLAMAX 00066 USE MODD_SURF_PAR, ONLY : XUNDEF 00067 USE MODD_DATA_COVER_PAR, ONLY : NVT_SNOW 00068 ! 00069 ! 00070 USE YOMHOOK ,ONLY : LHOOK, DR_HOOK 00071 USE PARKIND1 ,ONLY : JPRB 00072 ! 00073 IMPLICIT NONE 00074 ! 00075 !* 0.1 declarations of arguments 00076 ! 00077 ! 00078 LOGICAL, INTENT(IN) :: OGLACIER ! True = Over permanent snow and ice, 00079 ! initialise WGI=WSAT, 00080 ! Hsnow>=10m and allow 0.8<SNOALB<0.85 00081 ! False = No specific treatment 00082 REAL, INTENT(IN) :: PTSTEP 00083 ! timestep of the integration 00084 REAL, DIMENSION(:,:), INTENT(IN) :: PVEGTYPE ! fraction of each vegetation 00085 REAL, DIMENSION(:), INTENT(IN) :: PSR, PLES, PMELT 00086 ! PSR = snow rate 00087 ! PLES = latent heat of sublimation over the snow 00088 ! PMELT = melting rate of snow 00089 REAL, DIMENSION(:), INTENT(INOUT) :: PSNOWSWE, PSNOWALB, PSNOWRHO, PPG_MELT 00090 ! PSNOWSWE = equivalent water content of the 00091 ! snow reservoir at time 't+dt' 00092 ! PSNOWALB = albedo of the snow at 't+dt' 00093 ! PSNOWRHO = density of the snow at 't+dt' 00094 ! PPG_MELT = total water reaching the ground 00095 ! 00096 !* 0.2 declarations of local variables 00097 ! 00098 REAL, DIMENSION(SIZE(PSR)) :: ZSNOWSWEM, ZWSX, ZANSMIN, ZANSMAX 00099 ! Prognostic variables of ISBA at 't-dt' 00100 ! ZSNOWSWEM = equivalent water content of the 00101 ! snow reservoir 00102 ! ZANSMIN = Minimum glacier albedo 00103 ! ZANSMAX = Maximum glacier albedo 00104 REAL(KIND=JPRB) :: ZHOOK_HANDLE 00105 ! 00106 !------------------------------------------------------------------------------- 00107 IF (LHOOK) CALL DR_HOOK('HYDRO_SNOW',0,ZHOOK_HANDLE) 00108 !------------------------------------------------------------------------------- 00109 ! 00110 !* Douville et al. (1995) 'DEF' snow option 00111 ! ---------------------------------------- 00112 ! 00113 !* 1. Initialize: 00114 ! ----------- 00115 ! 00116 ZWSX(:) = 0.0 00117 ZANSMIN(:) = XANSMIN 00118 ZANSMAX(:) = XANSMAX 00119 ! 00120 ! 00121 !* 2. Fields at time t-dt 00122 ! ------------------- 00123 ! 00124 ZSNOWSWEM (:) = PSNOWSWE(:) 00125 ! 00126 !* 3. EVOLUTION OF THE SNOWPACK ('DEF' OPTION) 00127 ! ---------------------------------------- 00128 ! 00129 !* 3.A EVOLUTION OF THE EQUIVALENT WATER CONTENT snowSWE ('DEF' option) 00130 ! -------------------------------------------------------------- 00131 ! 00132 ! evolution of Ws (without melting) 00133 ! 00134 PSNOWSWE(:) = ZSNOWSWEM(:) + PTSTEP * ( PSR(:) - PLES(:)/XLSTT - PMELT(:)) 00135 ! 00136 ! melting of snow: more liquid water 00137 ! reaches the surface 00138 ! 00139 PPG_MELT(:) = PPG_MELT(:) + PMELT(:) 00140 ! 00141 ! removes very small values due to computation precision 00142 ! 00143 WHERE(PSNOWSWE(:) < 1.0E-10) PSNOWSWE(:) = 0. 00144 ! 00145 !------------------------------------------------------------------------------- 00146 ! 00147 !* 3.B EVOLUTION OF SNOW ALBEDO 00148 ! ------------------------ 00149 ! 00150 IF(OGLACIER)THEN 00151 ZANSMIN(:) = XAGLAMIN * PVEGTYPE(:,NVT_SNOW) + XANSMIN * (1.0-PVEGTYPE(:,NVT_SNOW)) 00152 ZANSMAX(:) = XAGLAMAX * PVEGTYPE(:,NVT_SNOW) + XANSMAX * (1.0-PVEGTYPE(:,NVT_SNOW)) 00153 ELSE 00154 ZANSMIN(:) = XANSMIN 00155 ZANSMAX(:) = XANSMAX 00156 ENDIF 00157 ! the evolution of the snow albedo differs 00158 ! if there is melting or not 00159 ! 00160 WHERE (PSNOWSWE > 0.0 ) 00161 ! 00162 WHERE ( ZSNOWSWEM > 0.0) 00163 ! 00164 ! when there is melting 00165 WHERE ( PMELT > 0.0 ) 00166 PSNOWALB(:) = (PSNOWALB(:)-ZANSMIN(:))*EXP(-XANS_T*PTSTEP/XDAY) + ZANSMIN(:) & 00167 + PSR(:)*PTSTEP/XWCRN*(ZANSMAX(:)-ZANSMIN(:)) 00168 ! when there is no melting 00169 ELSEWHERE 00170 PSNOWALB(:) = PSNOWALB(:) - XANS_TODRY*PTSTEP/XDAY & 00171 + PSR(:)*PTSTEP/XWCRN*(ZANSMAX(:)-ZANSMIN(:)) 00172 END WHERE 00173 ! 00174 ELSEWHERE (ZSNOWSWEM == 0.0) 00175 ! 00176 ! new snow covered surface 00177 PSNOWALB(:) = ZANSMAX(:) 00178 END WHERE 00179 ! 00180 ! limits of the albedo 00181 PSNOWALB(:) = MIN( ZANSMAX(:), PSNOWALB(:) ) 00182 PSNOWALB(:) = MAX( ZANSMIN(:), PSNOWALB(:) ) 00183 END WHERE 00184 ! 00185 !------------------------------------------------------------------------------- 00186 ! 00187 !* 3.C EVOLUTION OF SNOW DENSITY 00188 ! ------------------------- 00189 ! 00190 ! as for the snow albedo, the density's 00191 ! evolution will depend whether or not 00192 ! the snow is melting 00193 ! 00194 WHERE ( PSNOWSWE > 0.0 ) 00195 WHERE ( ZSNOWSWEM > 0.0 ) 00196 ZWSX(:) = MAX( PSNOWSWE(:),PSR(:)*PTSTEP) 00197 PSNOWRHO(:) = (PSNOWRHO(:)-XRHOSMAX)*EXP(-XANS_T*PTSTEP/XDAY) + XRHOSMAX 00198 PSNOWRHO(:) = ( (ZWSX(:)-PSR(:)*PTSTEP) * PSNOWRHO(:) & 00199 + (PSR(:)*PTSTEP) * XRHOSMIN ) / ZWSX(:) 00200 ELSEWHERE ( ZSNOWSWEM == 0.0) 00201 PSNOWRHO(:) = XRHOSMIN 00202 END WHERE 00203 END WHERE 00204 ! 00205 !------------------------------------------------------------------------------- 00206 ! 00207 !* 4. No SNOW 00208 ! ------- 00209 ! 00210 WHERE ( PSNOWSWE == 0.0 ) 00211 PSNOWRHO(:) = XUNDEF 00212 PSNOWALB(:) = XUNDEF 00213 END WHERE 00214 ! 00215 IF (LHOOK) CALL DR_HOOK('HYDRO_SNOW',1,ZHOOK_HANDLE) 00216 ! 00217 !------------------------------------------------------------------------------- 00218 ! 00219 END SUBROUTINE HYDRO_SNOW
1.8.0
