| 1 | MODULE trasbc |
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| 2 | !!============================================================================== |
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| 3 | !! *** MODULE trasbc *** |
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| 4 | !! Ocean active tracers: surface boundary condition |
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| 5 | !!============================================================================== |
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| 6 | !! History : OPA ! 2998-10 (G. Madec, G. Roullet, M. Imbard) Original code |
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| 7 | !! 8.2 ! 2001-02 (D. Ludicone) sea ice and free surface |
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| 8 | !! NEMO 1.0 ! 2002-06 (G. Madec) F90: Free form and module |
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| 9 | !! 3.3 ! 2010-04 (M. Leclair, G. Madec) Forcing averaged over 2 time steps |
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| 10 | !!---------------------------------------------------------------------- |
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| 11 | |
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| 12 | !!---------------------------------------------------------------------- |
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| 13 | !! tra_sbc : update the tracer trend at ocean surface |
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| 14 | !!---------------------------------------------------------------------- |
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| 15 | USE oce ! ocean dynamics and active tracers |
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| 16 | USE sbc_oce ! surface boundary condition: ocean |
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| 17 | USE dom_oce ! ocean space domain variables |
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| 18 | USE phycst ! physical constant |
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| 19 | USE traqsr ! solar radiation penetration |
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| 20 | USE trdmod ! ocean trends |
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| 21 | USE trdmod_oce ! ocean variables trends |
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| 22 | USE in_out_manager ! I/O manager |
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| 23 | USE prtctl ! Print control |
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| 24 | |
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| 25 | IMPLICIT NONE |
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| 26 | PRIVATE |
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| 27 | |
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| 28 | PUBLIC tra_sbc ! routine called by step.F90 |
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| 29 | |
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| 30 | !! * Substitutions |
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| 31 | # include "domzgr_substitute.h90" |
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| 32 | # include "vectopt_loop_substitute.h90" |
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| 33 | !!---------------------------------------------------------------------- |
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| 34 | !! NEMO/OPA 3.3 , LOCEAN-IPSL (2010) |
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| 35 | !! $Id$ |
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| 36 | !! Software governed by the CeCILL licence (modipsl/doc/NEMO_CeCILL.txt) |
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| 37 | !!---------------------------------------------------------------------- |
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| 38 | |
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| 39 | CONTAINS |
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| 40 | |
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| 41 | SUBROUTINE tra_sbc ( kt ) |
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| 42 | !!---------------------------------------------------------------------- |
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| 43 | !! *** ROUTINE tra_sbc *** |
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| 44 | !! |
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| 45 | !! ** Purpose : Compute the tracer surface boundary condition trend of |
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| 46 | !! (flux through the interface, concentration/dilution effect) |
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| 47 | !! and add it to the general trend of tracer equations. |
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| 48 | !! |
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| 49 | !! ** Method : Following Roullet and Madec (2000), the air-sea flux |
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| 50 | !! can be divided into three effects: |
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| 51 | !! (1) Fext, external forcing; |
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| 52 | !! (2) Fwi, concentration/dilution effect due to water exchanged |
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| 53 | !! at the surface by evaporation, precipitations and runoff (E-P-R); |
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| 54 | !! (3) Fwe, tracer carried with the water that is exchanged. |
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| 55 | !! |
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| 56 | !! Fext, flux through the air-sea interface for temperature and salt: |
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| 57 | !! - temperature : heat flux q (w/m2). If penetrative solar |
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| 58 | !! radiation q is only the non solar part of the heat flux, the |
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| 59 | !! solar part is added in traqsr.F routine. |
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| 60 | !! ta = ta + q /(rau0 rcp e3t) for k=1 |
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| 61 | !! - salinity : only salt flux exchanged with sea-ice |
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| 62 | !! |
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| 63 | !! The formulation for Fwb and Fwi vary according to the free |
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| 64 | !! surface formulation (linear or variable volume). |
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| 65 | !! * Linear free surface |
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| 66 | !! The surface freshwater flux modifies the ocean volume |
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| 67 | !! and thus the concentration of a tracer and the temperature. |
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| 68 | !! First order of the effect of surface freshwater exchange |
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| 69 | !! for salinity, it can be neglected on temperature (especially |
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| 70 | !! as the temperature of precipitations and runoffs is usually |
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| 71 | !! unknown). |
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| 72 | !! - temperature : we assume that the temperature of both |
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| 73 | !! precipitations and runoffs is equal to the SST, thus there |
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| 74 | !! is no additional flux since in this case, the concentration |
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| 75 | !! dilution effect is balanced by the net heat flux associated |
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| 76 | !! to the freshwater exchange (Fwe+Fwi=0): |
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| 77 | !! (Tp P - Te E) + SST (P-E) = 0 when Tp=Te=SST |
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| 78 | !! - salinity : evaporation, precipitation and runoff |
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| 79 | !! water has a zero salinity (Fwe=0), thus only Fwi remains: |
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| 80 | !! sa = sa + emp * sn / e3t for k=1 |
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| 81 | !! where emp, the surface freshwater budget (evaporation minus |
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| 82 | !! precipitation minus runoff) given in kg/m2/s is divided |
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| 83 | !! by 1035 kg/m3 (density of ocena water) to obtain m/s. |
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| 84 | !! Note: even though Fwe does not appear explicitly for |
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| 85 | !! temperature in this routine, the heat carried by the water |
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| 86 | !! exchanged through the surface is part of the total heat flux |
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| 87 | !! forcing and must be taken into account in the global heat |
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| 88 | !! balance). |
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| 89 | !! * nonlinear free surface (variable volume, lk_vvl) |
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| 90 | !! contrary to the linear free surface case, Fwi is properly |
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| 91 | !! taken into account by using the true layer thicknesses to |
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| 92 | !! calculate tracer content and advection. There is no need to |
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| 93 | !! deal with it in this routine. |
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| 94 | !! - temperature: Fwe=SST (P-E+R) is added to Fext. |
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| 95 | !! - salinity: Fwe = 0, there is no surface flux of salt. |
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| 96 | !! |
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| 97 | !! ** Action : - Update the 1st level of (ta,sa) with the trend associated |
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| 98 | !! with the tracer surface boundary condition |
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| 99 | !! - save the trend it in ttrd ('key_trdtra') |
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| 100 | !!---------------------------------------------------------------------- |
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| 101 | USE oce, ONLY : ztrdt => ua ! use ua as 3D workspace |
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| 102 | USE oce, ONLY : ztrds => va ! use va as 3D workspace |
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| 103 | !! |
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| 104 | INTEGER, INTENT(in) :: kt ! ocean time-step index |
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| 105 | !! |
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| 106 | INTEGER :: ji, jj ! dummy loop indices |
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| 107 | REAL(wp) :: zta, zsa, zsrau, zse3t ! temporary scalars |
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| 108 | !!---------------------------------------------------------------------- |
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| 109 | |
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| 110 | IF( kt == nit000 ) THEN |
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| 111 | IF(lwp) WRITE(numout,*) |
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| 112 | IF(lwp) WRITE(numout,*) 'tra_sbc : TRAcer Surface Boundary Condition' |
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| 113 | IF(lwp) WRITE(numout,*) '~~~~~~~ ' |
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| 114 | ENDIF |
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| 115 | |
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| 116 | zsrau = 1. / rau0 ! initialization |
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| 117 | #if defined key_zco |
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| 118 | zse3t = 1. / e3t_0(1) |
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| 119 | #endif |
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| 120 | |
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| 121 | IF( l_trdtra ) THEN ! Save ta and sa trends |
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| 122 | ztrdt(:,:,:) = ta(:,:,:) |
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| 123 | ztrds(:,:,:) = sa(:,:,:) |
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| 124 | ENDIF |
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| 125 | |
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| 126 | !!gm IF( .NOT.ln_traqsr ) qsr(:,:) = 0.e0 ! no solar radiation penetration |
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| 127 | IF( .NOT.ln_traqsr ) THEN ! no solar radiation penetration |
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| 128 | qns(:,:) = qns(:,:) + qsr(:,:) ! total heat flux in qns |
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| 129 | qsr(:,:) = 0.e0 ! qsr set to zero |
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| 130 | IF( kt == nit000 ) THEN ! idem on before field at nit000 |
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| 131 | qns_b(:,:) = qns_b(:,:) + qsr_b(:,:) |
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| 132 | qsr_b(:,:) = 0.e0 |
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| 133 | ENDIF |
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| 134 | ENDIF |
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| 135 | |
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| 136 | ! Concentration dillution effect on (t,s) |
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| 137 | !! DO jj = 2, jpj |
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| 138 | !! DO ji = fs_2, fs_jpim1 ! vector opt. |
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| 139 | !!#if ! defined key_zco |
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| 140 | !! zse3t = 1. / fse3t(ji,jj,1) |
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| 141 | !!#endif |
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| 142 | !! IF( lk_vvl) THEN |
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| 143 | !! zta = ro0cpr * qns(ji,jj) * zse3t & ! temperature : heat flux |
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| 144 | !! & - emp(ji,jj) * zsrau * tn(ji,jj,1) * zse3t ! & cooling/heating effet of EMP flux |
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| 145 | !! zsa = 0.e0 ! No salinity concent./dilut. effect |
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| 146 | !! ELSE |
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| 147 | !! zta = ro0cpr * qns(ji,jj) * zse3t ! temperature : heat flux |
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| 148 | !! zsa = emps(ji,jj) * zsrau * sn(ji,jj,1) * zse3t ! salinity : concent./dilut. effect |
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| 149 | !! ENDIF |
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| 150 | !! ta(ji,jj,1) = ta(ji,jj,1) + zta ! add the trend to the general tracer trend |
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| 151 | !! sa(ji,jj,1) = sa(ji,jj,1) + zsa |
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| 152 | !! END DO |
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| 153 | !! END DO |
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| 154 | |
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| 155 | ! ! ---------------------- ! |
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| 156 | IF( lk_vvl ) THEN ! Variable Volume case ! |
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| 157 | ! ! ---------------------- ! |
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| 158 | DO jj = 2, jpj |
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| 159 | DO ji = fs_2, fs_jpim1 ! vector opt. |
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| 160 | zse3t = 0.5 / fse3t(ji,jj,1) |
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| 161 | ! ! temperature: heat flux + cooling/heating effet of EMP flux |
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| 162 | ta(ji,jj,1) = ta(ji,jj,1) + ( ro0cpr * ( qns(ji,jj) + qns_b(ji,jj) ) & |
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| 163 | & - zsrau * ( emp(ji,jj) + emp_b(ji,jj) ) * tn(ji,jj,1) ) * zse3t |
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| 164 | ! ! salinity: salt flux |
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| 165 | sa(ji,jj,1) = sa(ji,jj,1) + ( emps(ji,jj) + emps_b(ji,jj) ) * zse3t |
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| 166 | |
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| 167 | !!gm BUG : in key_vvl emps must be modified to only include the salt flux due to with sea-ice freezing/melting |
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| 168 | !!gm otherwise this flux will be missing ==> modification required in limsbc, limsbc_2 and CICE interface. |
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| 169 | |
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| 170 | END DO |
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| 171 | END DO |
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| 172 | ! ! ---------------------- ! |
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| 173 | ELSE ! Constant Volume case ! |
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| 174 | ! ! ---------------------- ! |
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| 175 | DO jj = 2, jpj |
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| 176 | DO ji = fs_2, fs_jpim1 ! vector opt. |
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| 177 | zse3t = 0.5 / fse3t(ji,jj,1) |
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| 178 | ! ! temperature: heat flux |
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| 179 | ta(ji,jj,1) = ta(ji,jj,1) + ro0cpr * ( qns (ji,jj) + qns_b (ji,jj) ) * zse3t |
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| 180 | ! ! salinity: salt flux + concent./dilut. effect (both in emps) |
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| 181 | sa(ji,jj,1) = sa(ji,jj,1) + zsrau * ( emps(ji,jj) + emps_b(ji,jj) ) * sn(ji,jj,1) * zse3t |
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| 182 | END DO |
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| 183 | END DO |
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| 184 | ! |
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| 185 | ENDIF |
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| 186 | |
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| 187 | IF( l_trdtra ) THEN ! save the sbc trends for diagnostic |
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| 188 | ztrdt(:,:,:) = ta(:,:,:) - ztrdt(:,:,:) |
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| 189 | ztrds(:,:,:) = sa(:,:,:) - ztrds(:,:,:) |
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| 190 | CALL trd_mod(ztrdt, ztrds, jptra_trd_nsr, 'TRA', kt) |
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| 191 | ENDIF |
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| 192 | ! ! control print |
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| 193 | IF(ln_ctl) CALL prt_ctl( tab3d_1=ta, clinfo1=' sbc - Ta: ', mask1=tmask, & |
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| 194 | & tab3d_2=sa, clinfo2= ' Sa: ', mask2=tmask, clinfo3='tra' ) |
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| 195 | ! |
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| 196 | END SUBROUTINE tra_sbc |
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| 197 | |
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| 198 | !!====================================================================== |
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| 199 | END MODULE trasbc |
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