Changes between Version 5 and Version 6 of ticket/0663_MLF


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Timestamp:
2010-04-23T15:00:41+02:00 (11 years ago)
Author:
gm
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  • ticket/0663_MLF

    v5 v6  
    1313=== Description === 
    1414 
    15 Introduce the modified Leap-Frog -- Robert-Asselin filter (LF-RA) to fit the one presented in Leclair and Madec Ocean Modelling (2009). The scheme allows a exact conservation of the heat and salt contents when using variable volume thickness (key_vvl). The non-conservation of the standard LF-RA due to the time diffusion of the forcing through the filter. In the modified scheme the exact conservation is achieved by removing the forcing from the filter. Furthermore, the scheme allows to use a much smaller Asselin filter parameter (10^-4 instead of 10^-1) decreasing the damping effect of the LF-RA scheme, so that it is actually a quasi second order scheme. 
     15Introduce the modified Leap-Frog -- Robert-Asselin filter (LF-RA) to fit the one presented in Leclair and Madec Ocean Modelling (2009). The scheme allows a exact conservation of the heat and salt contents when using variable volume thickness (key_vvl). The non-conservation of the standard LF-RA due to the time diffusion of the forcing through the filter. In the modified scheme the exact conservation is achieved by removing the forcing from the filter. Furthermore, the scheme allows to use a much smaller Asselin filter parameter (10^-4^ instead of 10^-1^) decreasing the damping effect of the LF-RA scheme, so that it is actually a quasi second order scheme. 
    1616 
    1717The LF-RA flow chart of ''step'' is the one introduce in the trunk after the v3.1, to restore the key_vvl option. Its main characteristic is that the ''ssh'' is time-stepped first, followed immediately by the computation of the ''now'' vertical velocity (see figure below). [[BR]] 
     
    3434   Note that TKE equation is solved with a two level time stepping scheme : no need of a before field for its forcing term (i.e. taum) 
    3535 
    36    sbc_oce.F90 : add "before" forcing fields (denoted by a '_b' sufix) for all ocean forcing components (utau_b, vtau_b, qns_b, qsr_b, emp_b, emps_b) 
    37    sbcmod.F90 : add the swap of surface fields and the read/write in the restart file. 
    38       Beginning of sbs routine, introduce the swap, but only for kt >= nit000+1. If no restart, the '_b' fields is known only at the end of the sbc calculation. Therefore we have choosen to regroup the setting of '_b' fields at nit000 at the end of sbc routine. CAUTION : here the swap must be done at each kt, what ever the nn_fsbc value is. Otherwise the ocean forcing will be wrong. 
     36   '''sbc_oce.F90 :''' add "before" forcing fields (denoted by a '_b' sufix) for all ocean forcing components (utau_b, vtau_b, qns_b, qsr_b, emp_b, emps_b) 
     37    
     38   '''sbcmod.F90 :''' add the swap of surface fields and the read/write in the restart file. 
     39 
     40      Beginning of sbs routine, introduce the swap, but only for kt >= nit000+1. If no restart, the '_b' fields is known only at the end of the sbc calculation. Therefore we have choosen to regroup the setting of '_b' fields at nit000 at the end of sbc routine.  
     41 
     42      CAUTION : here the swap must be done at each kt, what ever the nn_fsbc value is. Otherwise the ocean forcing will be wrong. 
    3943 
    4044'''(2) The Asselin filter''' remove the forcing from the filter (dynnxt (?), tranxt, traqsr) 
    4145 
    42 '''(3) The semi-implicit hpg'''. In tranxt.F90, for the semi-implicit hydrostatic pressure gradient,  the coefficients are changed in order to take into account the Asselin filter parameter 
     46'''(3) The semi-implicit hpg'''. 
     47    In tranxt.F90, for the semi-implicit hydrostatic pressure gradient,  the coefficients are changed in order to take into account the Asselin filter parameter 
    4348 
    4449   time mean T and S for the semi implicit hpg computation was (ta+2*tn + tb) / 4 . It is now replaced by 
     
    5358 
    5459   Forcing evaluation : the momentum and tracers forcing are evaluated at kt+1/2, no-more at kt. This is done in the fldread routine since v3.0 
     60 
    5561   Flow chart : general structure has changed for key_vvl (variable volume or equivalently non-linear free surface) (v3.1). In particular the ssh equation is solved first together followed immediately by the computation of the now vertical velocity, so that wn is available to solve the tracer and the dynamics equations.  
    5662