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| 5 | <TITLE>PALM chapter 3.8</TITLE> |
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| 7 | <META NAME="AUTHOR" CONTENT="Siegfried Raasch"> |
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| 21 | <H3 STYLE="line-height: 100%">3.8 Coupled model runs</H3> |
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| 22 | <P STYLE="line-height: 100%">Starting from version 3.4 PALM allows |
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[349] | 23 | coupled atmosphere-ocean model runs. If MPI-2 support is available, <B>mrun</B> starts the coupled model as two |
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[344] | 24 | concurrent executables, the atmosphere version and the ocean |
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[349] | 25 | version in analogy with the modular structure of PALM.</P> |
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[344] | 26 | <P STYLE="line-height: 100%">Currently, the coupler is at an |
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| 27 | experimental stage using either a MPI2 (more flexible) or a MPI1 |
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| 28 | intercommunicator that matches the atmosphere and ocean processors |
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| 29 | one-to-one. This approach has limited flexibility and |
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| 30 | performance, because it requires identical horizontal numerical grids |
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| 31 | and it uses the same number of atmosphere and ocean processors, which |
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| 32 | does not necessarily guarrantee a good load balancing.</P> |
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| 33 | <P STYLE="line-height: 100%">The coupler establishes a one-way |
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| 34 | interaction between the atmosphere and the ocean. The atmosphere |
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| 35 | sends its bottom surface fluxes (temperature, humidity, momentum) to |
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| 36 | the ocean. The ocean sends its top surface temperature to the |
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| 37 | atmosphere. The atmosphere assumes saturation of humidity and zero |
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| 38 | wind speed at its bottom surface. For calculations with <A HREF="chapter_4.1.html#humidity">humidity</A> |
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| 39 | = .T. the atmospheric evaporation leads to a salinity flux in the |
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| 40 | ocean (see e.g. Steinhorn 1991, JPO 21, p. 1681).</P> |
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| 41 | <P STYLE="line-height: 100%">If the full MPI-2 standard is available, |
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| 42 | it can be activated by adding the preprocessor directive <TT><FONT SIZE=2>-D__mpi2</FONT></TT> |
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| 43 | to <TT><FONT SIZE=2>cpp_options</FONT></TT> in the .mrun.config |
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| 44 | configuration file. Otherwise, PALM will use a coupling via MPI1. To |
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| 45 | start a coupled model run, this must be requested with the <B>mrun</B> |
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[349] | 46 | option <TT><FONT SIZE=2>-Y â#1 #2â</FONT></TT>, |
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| 47 | where </TT><TT><FONT FACE="Andale Mono"><FONT SIZE=2>#1</FONT></FONT></TT> |
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| 48 | is the number of processors for the atmospheric and </FONT></FONT></TT><FONT FACE="Andale Mono"><FONT SIZE=2>#2</FONT></FONT></TT> |
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[344] | 49 | the number of processors for the oceanic version of PALM (Please note |
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[349] | 50 | that currently only one-to-one topologies are supported and </FONT></FONT></TT><TT><FONT FACE="Andale Mono"><FONT SIZE=2>#1</FONT></FONT></TT> |
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| 51 | must be equal to </FONT></FONT></TT><TT><FONT FACE="Andale Mono"><FONT SIZE=2>#2</FONT></FONT></TT><FONT FACE="Times New Roman, serif"><FONT SIZE=3>). |
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| 52 | </FONT></FONT></TT><FONT FACE="Times New Roman, serif"><FONT SIZE=3></FONT></FONT>This |
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[344] | 53 | tells <B>mrun</B> to start two PALM executables. Coupled runs are |
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| 54 | only possible in parallel mode, which means that the <B>mrun</B> |
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| 55 | option <TT><FONT SIZE=2>-K parallel</FONT></TT> must also be set. The |
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| 56 | <B>mrun</B> call for coupled runs has to include the following |
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| 57 | coupling-related options: |
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| 58 | </P> |
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| 59 | <UL> |
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| 60 | <P STYLE="line-height: 100%"><TT><FONT SIZE=2>mrun </FONT></TT><FONT SIZE=2>...</FONT><TT> |
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| 61 | </TT><TT><FONT SIZE=2>-K parallel -r âd3# d3o# </FONT></TT><FONT SIZE=2>...</FONT><TT>â |
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| 62 | </TT><TT><FONT SIZE=2>-X </FONT></TT><FONT SIZE=2>...</FONT><TT> </TT><TT><FONT SIZE=2>-Y |
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| 63 | â#1 #2â</FONT></TT><TT>.</TT></P> |
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| 64 | </UL> |
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| 65 | <P STYLE="line-height: 100%">The <TT><FONT SIZE=2>-X </FONT></TT><FONT SIZE=2>...</FONT><TT> </TT>option |
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[197] | 66 | here specifies the total number of processors assigned to the coupled |
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[344] | 67 | model. Currently, half of them are assigned to each of the two |
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| 68 | coupled executables. Therefore it is advisable to specify an even |
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| 69 | number with <TT><FONT SIZE=2>-X </FONT></TT><FONT SIZE=2>...</FONT><TT> |
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| 70 | </TT>. Otherwise, in case of an odd total number of processors, one |
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| 71 | processor remains idle.</P> |
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| 72 | <P STYLE="line-height: 100%">Each coupled executable has its own, |
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| 73 | unique set of I/O filenames; <A HREF="chapter_3.4.html#coupled">chapter |
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| 74 | 3.4</A> gives information on file name conventions of coupled runs. |
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| 75 | The configuration file .mrun.config has to be extended for coupled |
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| 76 | runs. It is recommended to duplicate existing file connection |
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| 77 | identifiers such as "d3#", "pr#" etc. using the |
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| 78 | coupled ocean filenames accordingly. For example, the example of |
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| 79 | the previous chapters could be duplicated as follows:</P> |
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| 80 | <PRE STYLE="line-height: 100%"><A HREF="chapter_3.4.html#PARIN"><FONT SIZE=2>PARIN</FONT></A> <FONT SIZE=2>in:job:npe d3# ~/palm/current_version/JOBS/$fname/INPUT _p3d</FONT> |
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| 81 | <FONT SIZE=2>PARIN in:job:npe d3f ~/palm/current_version/JOBS/$fname/INPUT _p3df</FONT> |
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| 82 | <A HREF="chapter_3.4.html#BININ"><FONT SIZE=2>BININ</FONT></A> <FONT SIZE=2>in:loc d3f ~/palm/current_version/JOBS/$fname/OUTPUT _d3d</FONT> |
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| 83 | <FONT SIZE=2>#</FONT> |
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| 84 | <A HREF="chapter_3.4.html#BINOUT"><FONT SIZE=2>BINOUT</FONT></A> <FONT SIZE=2>out:loc restart ~/palm/current_version/JOBS/$fname/OUTPUT _d3d</FONT> |
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| 85 | <FONT SIZE=2>#</FONT> |
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| 86 | <A HREF="chapter_3.4.html#RUN_CONTROL"><FONT SIZE=2>RUN_CONTROL</FONT></A> <FONT SIZE=2>out:loc:tr d3# ~/palm/current_version/JOBS/$fname/MONITORING _rc</FONT> |
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| 87 | <A HREF="chapter_3.4.html#HEADER"><FONT SIZE=2>HEADER</FONT></A> <FONT SIZE=2>out:loc:tr d3# ~/palm/current_version/JOBS/$fname/MONITORING _header</FONT> |
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| 88 | <A HREF="chapter_3.4.html#PLOT1D_PAR"><FONT SIZE=2>PLOT1D_PAR</FONT></A> <FONT SIZE=2>out:loc:tr pr# ~/palm/current_version/JOBS/$fname/OUTPUT _pr_par</FONT> |
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| 89 | <A HREF="chapter_3.4.html#PLOT1D_DATA"><FONT SIZE=2>PLOT1D_DATA</FONT></A> <FONT SIZE=2>out:loc:tr pr# ~/palm/current_version/JOBS/$fname/OUTPUT _pr_in</FONT> |
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| 90 | <FONT SIZE=2>#</FONT> |
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| 91 | <FONT SIZE=2>PARIN</FONT><FONT SIZE=2><B>_O</B></FONT><FONT SIZE=2> in:job:npe d3</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2># ~/palm/current_version/JOBS/$fname/INPUT </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_p3d</FONT> |
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| 92 | <FONT SIZE=2>PARIN</FONT><FONT SIZE=2><B>_O</B></FONT><FONT SIZE=2> in:job:npe d3</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2>f ~/palm/current_version/JOBS/$fname/INPUT </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_p3df</FONT> |
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| 93 | <FONT SIZE=2>BININ</FONT><FONT SIZE=2><B>_O</B></FONT><FONT SIZE=2> in:loc d3</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2>f ~/palm/current_version/JOBS/$fname/OUTPUT </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_d3d</FONT> |
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| 94 | <FONT SIZE=2>#</FONT> |
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| 95 | <FONT SIZE=2>BINOUT</FONT><FONT SIZE=2><B>_O</B></FONT><FONT SIZE=2> out:loc restart ~/palm/current_version/JOBS/$fname/OUTPUT </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_d3d</FONT> |
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| 96 | <FONT SIZE=2>#</FONT> |
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| 97 | <FONT SIZE=2>RUN_CONTROL</FONT><FONT SIZE=2><B>_O</B></FONT> <FONT SIZE=2>out:loc:tr d3</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2># ~/palm/current_version/JOBS/$fname/MONITORING </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_rc</FONT> |
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| 98 | <FONT SIZE=2>HEADER</FONT><FONT SIZE=2><B>_O</B></FONT><FONT SIZE=2> out:loc:tr d3</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2># ~/palm/current_version/JOBS/$fname/MONITORING </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_header</FONT> |
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| 99 | <FONT SIZE=2>PLOT1D_PAR</FONT><FONT SIZE=2><B>_O</B></FONT> <FONT SIZE=2>out:loc:tr pr</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2># ~/palm/current_version/JOBS/$fname/OUTPUT </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_pr_par</FONT> |
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| 100 | <FONT SIZE=2>PLOT1D_DATA</FONT><FONT SIZE=2><B>_O</B></FONT><FONT SIZE=2> out:loc:tr pr</FONT><FONT SIZE=2><B>o</B></FONT><FONT SIZE=2># ~/palm/current_version/JOBS/$fname/OUTPUT </FONT><FONT SIZE=2><B>_o</B></FONT><FONT SIZE=2>_pr_in</FONT></PRE><P STYLE="line-height: 100%"> |
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| 101 | The coupled ocean model filenames in the first column (e.g. |
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| 102 | <A HREF="chapter_3.4.html#PARIN"><FONT SIZE=2>PARIN_O</FONT></A>) must |
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| 103 | be specified as given in <A HREF="chapter_3.4.html#coupled">chapter |
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| 104 | 3.4</A>; the file connection identifiers (e.g. <FONT SIZE=2>d3o#</FONT>) |
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| 105 | and the file name extension (e.g. <FONT SIZE=2>_o_p3d</FONT>) |
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| 106 | may be changed at the user's discretion.</P> |
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| 107 | <P STYLE="line-height: 100%">The coupler requires the following |
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| 108 | parameters to be equal in both <A HREF="chapter_3.4.html#PARIN"><FONT SIZE=2>PARIN</FONT></A> |
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| 109 | and <A HREF="chapter_3.4.html#PARIN"><FONT SIZE=2>PARIN_O</FONT></A>: |
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| 110 | <A HREF="chapter_4.1.html#dx">dx</A>, <A HREF="chapter_4.1.html#dy">dy</A>, |
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| 111 | <A HREF="chapter_4.1.html#nx">nx</A>, <A HREF="chapter_4.1.html#ny">ny</A>, |
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| 112 | <A HREF="chapter_4.2.html#dt_coupling">dt_coupling</A>, <A HREF="chapter_4.2.html#end_time">end_time</A>, |
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| 113 | <A HREF="chapter_4.2.html#restart_time">restart_time</A>, <A HREF="chapter_4.2.html#dt_restart">dt_restart</A>. |
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| 114 | In the coupled atmosphere executable, <A HREF="chapter_4.2.html#bc_pt_b">bc_pt_b</A> |
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| 115 | is internally set and does not need to be prescribed; in the coupled |
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| 116 | ocean executable, <A HREF="chapter_4.2.html#bc_uv_t">bc_uv_t</A> is |
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[197] | 117 | internally set ('neumann') and does not need to be prescribed. The |
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[344] | 118 | coupled ocean parameter file <A HREF="chapter_3.4.html#PARIN"><FONT SIZE=2>PARIN_O</FONT></A> |
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| 119 | should include dummy REAL value assignments to both |
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| 120 | <A HREF="chapter_4.1.html#top_momentumflux_u">top_momentumflux_u</A> |
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| 121 | and <A HREF="chapter_4.1.html#top_momentumflux_v">top_momentumflux_v</A> |
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[197] | 122 | (e.g. top_momentumflux_u = 0.0, top_momentumflux_v = 0.0) to |
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[344] | 123 | enable the momentum flux coupling.</P> |
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| 124 | <P STYLE="line-height: 100%">The coupling interval <A HREF="chapter_4.2.html#dt_coupling">dt_coupling</A> |
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[197] | 125 | must be explicity set. In order to ensure synchronous coupling |
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[344] | 126 | throughout the simulation, <A HREF="chapter_4.2.html#dt_coupling">dt_coupling</A> |
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| 127 | should be chosen larger than <A HREF="chapter_4.2.html#dt_max">dt_max</A>.</P> |
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| 128 | <P STYLE="line-height: 100%">It's also possible to perform precursor |
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| 129 | runs (one atmospheric and one oceanic) followed by a coupled restart |
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[420] | 130 | run. In order to achieve this, the parameter <A HREF="chapter_4.1.html#coupling_start_time">coupling_start_time</A> |
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[344] | 131 | must be set according to the <A HREF="../misc/precursor_run_control.pdf">documentation.</A></P> |
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| 132 | <HR> |
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| 134 | <P STYLE="line-height: 100%"><I>Last change: </I> $Id: |
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| 135 | chapter_3.8.html 197 2008-09-16 15:29:03Z raasch $</P> |
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