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Next: 3.21 A Rotating Tank Up: 3.20 Offline Example Previous: 3.20.4 Running The Example   Contents

Subsections


3.20.5 A more complicated example

(in directory: verification/tutorial_cfc_offline/)

The last example demonstrated simple advection of a passive tracer using the offline form of the MITgcm. Now we present a more complicated example in which the model is used to explore contamination of the global ocean through surface exposure to CFC's during the last century. In invoking packages gchem, gmredi and cfc it provides a starting point and template for more complicated offline modeling, involving as it does surface forcing through wind and ice fields, more sophisticated mixing and a time-varying forcing funtion.



The model configuration for this experiment resides under the directory verification/cfc_offline. The experiment files

  • input/data
  • input/data.gchem
  • input/data.gmredi
  • input/data.off
  • input/data.pkg
  • input/data.ptracers
  • input/eedata
  • code/GCHEM_OPTIONS.h
  • code/GMREDI_OPTIONS.h
  • input/packages.conf
  • code/PTRACERS_SIZE.h
  • code/SIZE.h.

contain all the code customisations and parameter settings required.

The full list of other files required becomes:

cfc1112.atm  data.ptracers   
data         depth_g77.bin   pickup.0004269600.data
data.gchem   eedata          
data.gmredi  ice.bin         pickup_ptracers.0004269600.data
data.off     data.pkg        tren_speed.bin

and

input_off/:
Convtave.0004248060.data  GM_Kwz-T.0004248060.data  uVeltave.0004248060.data
Convtave.0004248060.meta  GM_Kwz-T.0004248060.meta  uVeltave.0004248060.meta
Convtave.0004248720.data  GM_Kwz-T.0004248720.data  uVeltave.0004248720.data
Convtave.0004248720.meta  GM_Kwz-T.0004248720.meta  uVeltave.0004248720.meta
GM_Kwx-T.0004248060.data  Stave.0004248060.data     vVeltave.0004248060.data
GM_Kwx-T.0004248060.meta  Stave.0004248060.meta     vVeltave.0004248060.meta
GM_Kwx-T.0004248720.data  Stave.0004248720.data     vVeltave.0004248720.data
GM_Kwx-T.0004248720.meta  Stave.0004248720.meta     vVeltave.0004248720.meta
GM_Kwy-T.0004248060.data  Ttave.0004248060.data     wVeltave.0004248060.data
GM_Kwy-T.0004248060.meta  Ttave.0004248060.meta     wVeltave.0004248060.meta
GM_Kwy-T.0004248720.data  Ttave.0004248720.data     wVeltave.0004248720.data
GM_Kwy-T.0004248720.meta  Ttave.0004248720.meta     wVeltave.0004248720.meta

3.20.5.1 File input/data

A single line must be added (under PARM01, between lines 6 and 7) in file input/data from the previous example

 &PARM01
 implicitDiffusion=.TRUE.,
 &

When package GMREDI is used, the flag implicitDiffusion must be assigned the value .TRUE. For information about MITgcm package GMREDI see...



In this example the starting timestep nIter0 is set to 4269600 requiring model access to pickup files with the timetag 0004269600. The model will run for 4 timesteps (nTimeSteps = 4). In this case the frequencies with which permanent and rolling checkpoints (pChkptFreq and chkptFreq) have been set is sufficiently long to ensure that only one from the last timestep will be written. This is also true of the values that have been assigned to the frequency with which dumps are written (dumpFreq) and time averaging (taveFreq) is performed however since the model always dumps the state of the model when it stops without error a dump will be written with timetag 0004269604 upon completion.

3.20.5.2 File input/data.off

File input/data.off, reproduced in full below, specifies the prefixes and locations of additional input files required to run the offline model. Note that input/input_off contains only as many offline files as are required to successfully run for 4 timesteps. Where the GMREDI scheme was used in the forward run, as here, package GMREDI must again be invoked when running offline. In this example tracer is specified as having beeen introduced with a non-zero starttime, at timestep 4248000.

1   &OFFLINE_PARM01
2    UvelFile= '../input/input_off/uVeltave',
3    VvelFile= '../input/input_off/vVeltave',
4    WvelFile= '../input/input_off/wVeltave',
5    GMwxFile= '../input/input_off/GM_Kwx-T',
6    GMwyFile= '../input/input_off/GM_Kwy-T',
7    GMwzFile= '../input/input_off/GM_Kwz-T',
8    ConvFile= '../input/input_off/Convtave',
9   &end

10  &OFFLINE_PARM02
11   offlineIter0=4248000,
12   deltaToffline=43200.,
13   offlineForcingPeriod=2592000.,
14   offlineForcingCycle=31104000.,
15  &end

3.20.5.3 File input/data.pkg

File input/data.pkg, reproduced completely below, specifies which MITgcm packages ( /MITgcm/pkg) are to be used. It now invokes additional packages pkg/gmredi and pkg/gchem.

1  # Packages
2   &PACKAGES
3   useGMRedi=.TRUE.,
4   usePTRACERS=.TRUE.,
5   useGCHEM=.TRUE.,
6   &

3.20.5.4 File input/data.ptracers

File input/data.ptracers, reproduced completely below, specifies parameters associated with the CFC11 and CFC12 tracer fields advected in this example.

  • Line 3
      PTRACERS_Iter0= 4248000,
    

In this example the tracers were introduced at iteration 4248000.

  • Lines 7 and 14
      PTRACERS_diffKh(n)=0.E3,
    

Since package GMREDI is being used, regular horizontal diffusion is set to zero.

  • Lines 9,10 and 16,17
      PTRACERS_useGMRedi(n)=.TRUE. ,
      PTRACERS_useKPP(n)=.FALSE. ,
    

Setting flag PTRACERS_useGMRedi(n) to .TRUE. identifies that package GMREDI is to be used. Setting flag PTRACERS_useKPP(n) to .FALSE. explicitly turns off KPP mixing.

  • Lines 11 and 18
     PTRACERS_initialFile(n)=' ',
    

Since this is a `pickup' run the initial tracer files PTRACERS_initialFile(1) and PTRACERS_initialFile(2) aree not needed. The model will obtain the tracer state from pickup_ptracers.0004269600.data

1   &PTRACERS_PARM01
2   PTRACERS_numInUse=2,
3   PTRACERS_Iter0= 4248000,
4  #
5  # tracer 1 - CFC11
6   PTRACERS_advScheme(1)=77,
7   PTRACERS_diffKh(1)=0.E3,
8   PTRACERS_diffKr(1)=5.E-5,
9   PTRACERS_useGMRedi(1)=.TRUE. ,
10  PTRACERS_useKPP(1)=.FALSE. ,
11  PTRACERS_initialFile(1)=' ',
12 # tracer 2 - CFC12
13  PTRACERS_advScheme(2)=77,
14  PTRACERS_diffKh(2)=0.E3,
15  PTRACERS_diffKr(2)=5.E-5,
16  PTRACERS_useGMRedi(2)=.TRUE. ,
17  PTRACERS_useKPP(2)=.FALSE. ,
18  PTRACERS_initialFile(2)=' ',
19  &

3.20.5.5 File input/data.gchem

File input/data.gchem, reproduced completely below, names the forcing files needed in package GCHEM.

  • Line 3
       iceFile='ice.bin',
    

File input/ice.bin contains 12, monthly surface ice fields.

  • Line 3
       iceFile='tren_speed.bin',
    

File input/tren_speed.bin contains 12, monthly surface wind fields.

1   &GCHEM_PARM01
2    iceFile='fice.bin',
3    windFile='tren_speed.bin',
4   &

Package GCHEM is described in detail in section ??

3.20.5.6 File input/data.gmredi

File input/data.gmredi, reproduced completely below, provides the parameters required for package GMREDI.

1   &GM_PARM01
2    GM_background_K    = 1.e+3,
3    GM_taper_scheme    = 'gkw91',
4    GM_maxSlope        = 1.e-2,
5    GM_Kmin_horiz      = 100.,
6    GM_Scrit           = 4.e-3,
7    GM_Sd              = 1.e-3,
8   &

Package GMREDI is described in detail in section ??

3.20.5.7 File input/cfc1112.atm

File input/cfc1112.atm is a text file containing the CFC source functions over the northern and southern hemispheres annually from 1931 through 1998.

3.20.5.8 File code/packages.conf

In this example code/packages.conf additionally invokes components gchem, cfc and rmredi:

ptracers
generic_advdiff
mdsio
mom_fluxform
mom_vecinv
timeave
rw
monitor
offline
gchem
cfc
gmredi

3.20.5.9 File code/GCHEM_OPTIONS.h

File code/GCHEM_OPTIONS.h, specifies options for package GCHEM. In this case defining the flag ALLOW_CFC to activate the cfc code.

3.20.5.10 File code/GMREDI_OPTIONS.h

File code/GCHEM_OPTIONS.h, specifies options for package GMREDI.

3.20.5.11 File code/PTRACERS_SIZE.h

File code/PTRACERS_SIZE.h is unchanged from the simpler example.

3.20.5.12 File code/SIZE.h

File code/SIZE.h is unchanged from the simpler example.

3.20.5.13 Running the Experiment

The model is run as before and produces the files the model generates describing the grid (prefixed Depth, DXC, DXG, hFacC, hFacS and hFacW) as well as 2, single precision, binary files PTRACER01.0004269600-0004269604.001.001.data and PTRACER02.0004269600-0004269604.001.001.data and their 2 corresponding meta files as well as a single pickup file, pickup_ptracers.ckptA.001.001.data and its corresponding meta file pickup_ptracers.ckptA.001.001.meta from which you could run the model on.


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Next: 3.21 A Rotating Tank Up: 3.20 Offline Example Previous: 3.20.4 Running The Example   Contents
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