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b29547f131 Oliv*0001 Package longstep
0002 ================
0003
0004 This package allows the passive tracer time step to be longer than that for
0005 dynamical fields: the ptracers are updated only every LS_nIter time step.
0006 Dynamical fields are averaged over LS_nIter time steps and are available as
0007 fields LS_* (declared in LONGSTEP.h):
0008
0009 original fld. averaged fld.
0010 ------------------------------
0011 UVEL LS_uVel
0012 VVEL LS_vVel
0013 WVEL LS_wVel
0014 THETA LS_theta
0015 SALT LS_salt
0016 IVDConvCount LS_IVDConvCount
0017 Qsw LS_Qsw
0018
0019 Kwx LS_Kwx
0020 Kwy LS_Kwy
0021 Kwz LS_Kwz
0022
0023 KPPdiffKzS LS_KPPdiffKzS
0024 KPPghat LS_KPPghat
0025
0026 The T and S time step remains the same as that for u,v,...
0027
0028
0029 Packages that use ptracers (like DIC) need to be adapted:
0030
0031 1. replace dtTracerLev by PTRACERS_dTLev
0032 2. replace THETA, SALT, etc. by their longstep averages from the table above.
0033 This should be made between #ifdef ALLOW_LONGSTEP ... #endif.
0034 (You need to #include "LONGSTEP.h")
0035
0036 The package is activated by including "longstep" in packages.conf. There is
0037 no "use_LONGSTEP", the package is always on when compiled.
0038
0039
0040 The run-time parameters are set in data.longstep. The default is:
0041
0042 &LONGSTEP_PARM01
0043 LS_nIter=1,
fda3710353 Oliv*0044 LS_whenToSample=0,
b29547f131 Oliv*0045 &
0046
fda3710353 Oliv*0047 LS_nIter :: number of dynamical time steps between ptracer time steps.
0048 LS_whenToSample :: when to sample dynamical fields for the longstep average
0049 0 - at beginning of timestep (reproduces offline results)
0050 1 - after first THERMODYNAMICS but before DYNAMICS
0051 (use use old U,V,W for advection, but new T,S for GCHEM if
0052 staggerTimeStep=.FALSE.; reproduces online with
0053 staggerTimeStep=.FALSE. for LS_nIter=1)
0054 2 - after DYNAMICS and second THERMODYNAMICS
0055 (use new U,V,W and T,S; reproduces online with
0056 staggerTimeStep=.TRUE. for LS_nIter=1)
b29547f131 Oliv*0057
0058 Default is to sample dynamical fields at the beginning of the time step. This
fda3710353 Oliv*0059 reproduces results from offline runs with unshifted time averages used for the
0060 dynamical fields.
0061
0062 To have a time stepping closer to the online model (and reproduce results
0063 for LS_nIter=1), use
0064
0065 LS_whenToSample=1 if staggerTimeStep=.FALSE.
0066 LS_whenToSample=2 if staggerTimeStep=.TRUE.
b29547f131 Oliv*0067
