/[MITgcm]/manual/s_phys_pkgs/text/gchem.tex
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revision 1.2 by edhill, Tue Oct 12 18:16:03 2004 UTC revision 1.3 by mlosch, Mon Nov 29 00:47:04 2004 UTC
# Line 30  how they provide examples to use this pa Line 30  how they provide examples to use this pa
30  {\it GCHEM\_OPTIONS.h} includes the compiler options to be used  {\it GCHEM\_OPTIONS.h} includes the compiler options to be used
31  in any experiment. For instance \#define ALLOW\_CFC allows  in any experiment. For instance \#define ALLOW\_CFC allows
32  the CFC code to be run. An important compiler option is  the CFC code to be run. An important compiler option is
33   \#define PTRACERS\_SEPARATE\_FORCING which determined   \#define GCHEM\_SEPARATE\_FORCING which determined
34  how and when the tracer forcing is applied (see discussion  how and when the tracer forcing is applied (see discussion
35  on Forcing below).  on Forcing below).
36   There are further runtime parameters   There are further runtime parameters
# Line 65  forcing files that will be needed by the Line 65  forcing files that will be needed by the
65    
66  There are two routine used to initialize parameters and fields  There are two routine used to initialize parameters and fields
67  needed by the experiment packages. These are  needed by the experiment packages. These are
68  {\it gchem\_init\_fixed.F} which is called from packages\_init\_fixed.F, and  {\it gchem\_init\_fixed.F} which is called from \textit{packages\_init\_fixed.F}, and
69  {\it gchem\_init\_vari.F} called from  {\it gchem\_init\_vari.F} called from
70  packages\_init\_variable.F. The first should  packages\_init\_variable.F. The first should
71  be used to call a subroutine specific to the tracer experiment  be used to call a subroutine specific to the tracer experiment
# Line 80  which sets (or initializes) time fields Line 80  which sets (or initializes) time fields
80  {{\bf LOADING FIELDS}}\\  {{\bf LOADING FIELDS}}\\
81  External forcing fields used by the tracer experiment are read  External forcing fields used by the tracer experiment are read
82  in by a subroutine (specific to the tracer experiment) called from  in by a subroutine (specific to the tracer experiment) called from
83  {\it gchem\_fields\_load.F}. This latter is called from forward\_step.F.  {\it gchem\_fields\_load.F}. This latter is called from \textit{forward\_step.F}.
84    
85  \vspace{.5cm}  \vspace{.5cm}
86    
# Line 93  between tracers) to these fields are tak Line 93  between tracers) to these fields are tak
93  interface. For tracers that are essentially passive (e.g. CFC's)  interface. For tracers that are essentially passive (e.g. CFC's)
94  but may have some surface boundary conditions  but may have some surface boundary conditions
95  this can easily be done within the regular tracer timestep. In this case  this can easily be done within the regular tracer timestep. In this case
96  {\it gchem\_forcing\_int.F} is called from ptracers\_integrate.F.  {\it gchem\_calc\_tendency.F} is called from {\it forward\_step.F}, where the
97    reactive (as opposed to the advective diffusive) tendencies are computed.
98    These tendencies, stored on the 3D field \textbf{gchemTendency}, are added to
99    the passive tracer tendencies \textbf{gPtr} in {\it gchem\_add\_tendency.F},
100    which is called from {\it ptracers\_forcing.F}.
101  For tracers with more complicated dependencies on each other,  For tracers with more complicated dependencies on each other,
102  and especially tracers which require a smaller timestep than  and especially tracers which require a smaller timestep than
103  deltaTtracer, it will be easier to use {\it gchem\_forcing\_sep.F}  deltaTtracer, it will be easier to use {\it gchem\_forcing\_sep.F}
104  which is called from forward\_step.F. There is a  which is called from forward\_step.F. There is a
105  compiler option set in {\it GCHEM\_OPTIONS.h} that determines  compiler option set in {\it GCHEM\_OPTIONS.h} that determines
106  which method is used: \#define PTRACERS\_SEPARATE\_FORCING  which method is used: \#define GCHEM\_SEPARATE\_FORCING
107  does the latter where tracers are forced separately from the  does the latter where tracers are forced separately from the
108  advection-diffusion code, and \#undef PTRACERS\_SEPARATE\_FORCING  advection-diffusion code, and \#undef GCHEM\_SEPARATE\_FORCING
109  includes the forcing in the regular timestepping.  includes the forcing in the regular timestepping.
110    
111  \vspace{.5cm}  \vspace{.5cm}
112    
113  \noindent  \noindent
114  {{\bf DIAGNOSTICS}}\\  {{\bf DIAGNOSTICS}}\\
115  This package also includes routines {\it gchem\_monitor.F} and  This package also also used the passive tracer routine {\it ptracers\_monitor.F}
116  {\it gchem\_mon\_print.F} which print out tracer statistics  which prints out tracer statistics
117  as often as the model dynamic statistic diagnostics (dynsys) are written.  as often as the model dynamic statistic diagnostics (dynsys) are written (or
118    as prescribed by the runtime flag \textbf{PTRACERS\_monitorFreq}, set in {\it data.ptracers}).
119  There is also a placeholder for any tracer experiment  There is also a placeholder for any tracer experiment
120  specific diagnostics to be calculated and printed to files.  specific diagnostics to be calculated and printed to files.
121  This is done in {\it gchem\_diags.F}. For instance the time average CO2  This is done in {\it gchem\_diags.F}. For instance the time average CO2
122  air-sea fluxes, and sea surface pH (among others) are written  air-sea fluxes, and sea surface pH (among others) are written
123  out by dic\_biotic\_diags.F which is called from gchem\_diags.F.  out by {\it dic\_biotic\_diags.F} which is called from {\it gchem\_diags.F}.
124    
125  \subsection{Do's and Don'ts}  \subsection{Do's and Don'ts}
126    
127  The pkg ptracer is required with use with this pkg.  The pkg ptracer is required with use with this pkg. Also, as usual, the
128  By itself, gchem pkg will read in {\bf data.gchem} and will  runtime flag \textbf{useGCHEM} must be set to \textbf{.TRUE.} in \textbf{data.pkg}.
129  write out ptracer diagnostics. It requires tracer experiment  By itself, gchem pkg will read in \textbf{data.gchem} and will
130    write out gchem diagnostics. It requires tracer experiment
131  specific calls to do anything else (for instance the calls  specific calls to do anything else (for instance the calls
132  to dic and cfc pkgs).  to dic and cfc pkgs).
133    
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