Two-way coupling between global and nested GEOS-Chem models
On this page we provide a description of the PeKing University CouPLer version 1 (PKUCPL), which will ship with GEOS-Chem v10-01 and higher versions, to allow for two-way coupling between global and nested GEOS-Chem models. Users can couple a global model with any numbers of nested models, see below. It currently works with GEOS-5 (4x5, 2x2.5, 0.5x0.667) and GEOS-FP (4x5, 2x2.5, 0.25x0.3125) met data.
Contents
Overview
GEOS-Chem and other global chemical transport models are limited by coarse horizontal resolutions, not allowing for detailed representation of small-scale nonlinear processes over the pollutant source regions.
Here, we develop a PKUCPL (PeKing University CouPLer) coupler to implement the two-way coupling capability of the global GEOS-Chem CTM (at 2x2.5 or 4x5) and its three nested models (at 0.5x0.667 or 0.25x0.3125).
As of May 12, 2015, with GEOS-Chem v10.1, the global model can be coupled with 0.25x0.3125 nested models over Asia and North America (w/ GEOS-FP met fields), or with 0.5x0.667 nested models covering Asia, North America and Europe (w/ GEOS-5 met fields).
Users can choose to couple the global model with as many nested models as they wish, by simply modifying one line or so of the setup code (see below). It is easily done!
A global-multi-regional multi-layer two-way coupled system is under development. This system will integrate global (2x2.5 or 4x5), regional (0.5x0.625) and local (0.25x0.3125) models altogether. Please stay tuned.
More information can be found at our Peking University webpage
Lead developers
- Jintai Lin (Peking University)
- Yingying Yan (Peking University)
Description
NOTE: Information taken from the README file provided by Yingying Yan (23 Jun 2014)
Modifications to existing GEOS-Chem files
| File | Description |
|---|---|
| GeosCore/main.F | add the code of initialization, exchange, cleanup for two-way coupled model |
| GeosCore/exchange_mod.F | new file: contain variables & routines for data exchange across all models, in a two-way framework |
| GeosCore/Makefile | add code to compile exchange_mod.F |
| GeosUtil/time_mod.F | add code to define the timestep for data exchange between models |
| Makefile_header.mk | add options to compile for two-way coupled model |
--Bob Y. 15:09, 7 January 2015 (EST)
Files in the new PKUCPL subdirectory
| File | Description |
|---|---|
| Twoway.compile.sh | Bash script to compile the two-way coupled modeling |
| geos/ | contains the executable 'geos' compiled for global model |
| geosch/ | contains the executable 'geos' compiled for nested model in Asia |
| geosna/ | contains the executable 'geos' compiled for nested model in North America |
| geoseu/ | contains the executable 'geos' compiled for nested model in Europe |
| PKUCPL.F90 | modulate the normal DO-Loop of GeosCore/main.F, to coordinate all models |
| PKUCPL.sh | provide utility to run models in the right directories
|
| run | an executable, outputted from PKUCPL.F90 and PKUCPL.sh, to modulate all models. Users need to execute this file to finally activate the two-way coupled simulation.
Some examples (rundir is the run directory for two-way coupled simulation; codedir is the directory for code sources):
|
| run_twoway | batch job script to do two-way coupled simulation |
--Bob Y. 15:11, 7 January 2015 (EST)
Example run directory
| File | Description |
|---|---|
| run.v9-02.geos5.twoway/ | Master run directory, inside which there are the following subdirectories (listed below): |
| 2x25/ | Run directory for global model |
| 2x25/run_global | Batch job script to submit global model |
| CH/ | Run directory for nested model in Asia |
| CH/run_nested | Batch job script to submit nested CH model |
| EU/ | Run directory for nested model in Asia |
| EU/run_nested | Batch job script to submit nested NA model |
| NA/ | Run directory for nested model in Asia |
| NA/run_nested | Batch job script to submit nested NA model |
| lock/ | Directory for ancillary files communicating run imformation between models. Example files:
|
| exchange/ | Temporary directory to contain data for exchange between models |
--Bob Y. 15:20, 7 January 2015 (EST)
Setup steps
- Set up the run directories
- e.g., master run dir : /home/yanyy/geoschem/run/run.v9-02.geos5.twoway/
- run for Global 2x2.5 : /home/yanyy/geoschem/run/run.v9-02.geos5.twoway/2x25/
- run for Asia nested : /home/yanyy/geoschem/run/run.v9-02.geos5.twoway/CH/
- Set up the batch job script in run directories, as done for a normal GEOS-Chem run
- Go to PKUCPL/ in the code directory
- Make sure the run directories for individual models defined in PKUCPL.sh are consistent with the setup at the 1st step
- No need to change the variable 'rundir' in PKUCPL.sh -- It will be automatically corrected later
- Compile for two-way coupled model: ./Twoway.compile.sh
- This step generates the executables for all global/nested models, and an additional executable 'run' as a coupling master
- Copy the executable 'run' and the batch job script 'run_twoway' to the master run directory
- Go to the master run directory, and submit the batch job script 'run_twoway' for two-way simulation: qsub run_twoway
--Bob Y. 14:42, 7 January 2015 (EST)
References
Yan, Y.-Y., Lin, J.-T., Kuang, Y., Yang, D., and Zhang, L.: Tropospheric carbon monoxide over the Pacific during HIPPO: two-way coupled simulation of GEOS-Chem and its multiple nested models, Atmos. Chem. Phys., 14, 12649-12663, doi:10.5194/acp-14-12649-2014, 2014. Link
Yan, Y.-Y., Lin, J.-T., Chen, J., and Hu, L.: Improved simulation of tropospheric ozone by a global-multi-regional two-way coupling model system, Atmospheric Chemistry and Physics, 16, 2381-2400, doi:10.5194/acp-16-2381-2016, 2016. Link
