Changes between Version 7 and Version 8 of doc/app/examples/coupled

Timestamp:

Dec 26, 2010 9:44:54 PM (14 years ago)

Author:

gryschka

Comment:

--

doc/app/examples/coupled

@@ -3 +3 @@
 
 Starting from version 3.4 PALM allows coupled atmosphere-ocean model runs. If MPI-2 support is available, '''mrun''' starts the coupled model as two concurrent executables, the atmosphere version and the ocean version in analogy with the modular structure of PALM.\\\\
-The coupler establishes a one-way interaction between the atmosphere and the ocean. The atmosphere sends its bottom surface fluxes (temperature, humidity, momentum) to the ocean. The ocean sends its top surface temperature to the atmosphere. The atmosphere assumes saturation of humidity and zero wind speed at its bottom surface. For calculations with [../../inipar#humidity humidity] = ''.T.'' the atmospheric evaporation leads to a salinity flux in the ocean (see e.g. Steinhorn 1991, JPO 21, p. 1681).\\\\
-If the full MPI-2 standard is available, it can be activated by adding the preprocessor directive {{{-D__mpi2}}} to {{{cpp_options}}} in the {{{.mrun.config}}} configuration file. Otherwise, PALM will use a coupling via MPI1. Please note that coupling with different horizontal grid size and different number of processors in ocean and atmosphere is only possible with MPI-1. To start a coupled model run, this must be requested with the '''mrun''' option {{{-Y}}} {{{“#1 #2”}}}, where {{{#1}}} is the number of processors for the atmospheric and {{{#2}}} the number of processors for the oceanic version of PALM (Please note that currently only one-to-one topologies are supported and {{{#1}}} must be equal to {{{#2}}}). This tells '''mrun''' to start two PALM executables. Coupled runs are only possible in parallel mode, which means that the '''mrun''' option {{{-K parallel}}} must also be set. The '''mrun''' call for coupled runs has to include the following coupling-related options:
+The coupler establishes a one-way interaction between the atmosphere and the ocean. The atmosphere sends its bottom surface fluxes (temperature, humidity, momentum) to the ocean. The ocean sends its top surface temperature and top horizontal velocity to the atmosphere. The atmosphere assumes saturation of humidity and zero wind speed at its bottom surface. For calculations with [../../inipar#humidity humidity] = ''.T.'' the atmospheric evaporation leads to a salinity flux in the ocean (see e.g. Steinhorn 1991, JPO 21, p. 1681).\\\\
+If the full MPI-2 standard is available, it can be activated by adding the preprocessor directive {{{-D__mpi2}}} to {{{cpp_options}}} in the {{{.mrun.config}}} configuration file. Otherwise, PALM will use a coupling via MPI1. Please note that coupling with different horizontal grid size and different number of processors in ocean and atmosphere is only possible with MPI-1. To start a coupled model run, this must be requested with the '''mrun''' option {{{-Y}}} {{{“#1 #2”}}}, where {{{#1}}} is the number of processors for the atmospheric and {{{#2}}} the number of processors for the oceanic version of PALM. This tells '''mrun''' to start two PALM executables. Coupled runs are only possible in parallel mode, which means that the '''mrun''' option {{{-K parallel}}} must also be set. The '''mrun''' call for coupled runs has to include the following coupling-related options:
 {{{
       mrun ... -K parallel -r “d3# d3o# ...” -X ... -Y “#1 #2”.
 }}}
+To ensure a good balance concerning effective CPU-time in ocean and atmosphere the ratio of the number of processors in atmosphere ({{{#1}}})and in Ocean ({{{#2}}}) should be close to
+{{{#!Latex 
+\frac{\#1}{\#2} \approx\frac{(\Delta t)_{\mbox{O}}}{(\Delta t)_{\mbox{A}}} \frac{N_{\mbox{A}}}{N_{\mbox{O}}} ,
+}}}
+with 
+{{{
+#!Latex
+(\Delta t)_{\mbox{O}}, (\Delta t)_{\mbox{A}}
+}}}
+the expected averaged time step and  
+{{{
+#!Latex
+N_{\mbox{O}}, N_{\mbox{A}}
+}}}
+the total number of grid points in ocean and atmosphere.
+
 Each coupled executable has its own, unique set of I/O filenames. Information on file name conventions of coupled runs are given [../../iofiles here]. The configuration file {{{.mrun.config}}} has to be extended for coupled runs. It is recommended to duplicate existing file connection identifiers such as {{{"d3#"}}}, {{{"pr#"}}} etc. using the coupled ocean filenames accordingly. For example, the example of the previous chapters could be duplicated as follows:
 {{{