8.7.1. GCHEM Package¶
8.7.1.1. Introduction¶
This package has been developed as interface to the PTRACERS package. The purpose is to provide a structure where various (any) tracer experiments can be added to the code. For instance there are placeholders for routines to read in parameters needed for any tracer experiments, a routine to read in extra fields required for the tracer code, routines for either external forcing or internal interactions between tracers and routines for additional diagnostics relating to the tracers. Note that the gchem package itself is only a means to call the subroutines used by specific biogeochemical experiments, and does not “do” anything on its own.
There are two examples: cfc which looks at 2 tracers with a simple external forcing and dic with 4,5 or 6 tracers whose tendency terms are related to one another. We will discuss these here only as how they provide examples to use this package.
8.7.1.2. Key subroutines and parameters¶
8.7.1.3. GCHEM Diagnostics¶
These diagnostics are particularly for the dic package.
------------------------------------------------------------------------
<-Name->|Levs|<-parsing code->|<-- Units -->|<- Tile (max=80c)
------------------------------------------------------------------------
DICBIOA | 15 |SM P MR |mol/m3/sec |Biological Productivity (mol/m3/s)
DICCARB | 15 |SM P MR |mol eq/m3/sec |Carbonate chg-biol prod and remin (mol eq/m3/s)
DICTFLX | 1 |SM P L1 |mol/m3/sec |Tendency of DIC due to air-sea exch (mol/m3/s)
DICOFLX | 1 |SM P L1 |mol/m3/sec |Tendency of O2 due to air-sea exch (mol/m3/s)
DICCFLX | 1 |SM P L1 |mol/m2/sec |Flux of CO2 - air-sea exch (mol/m2/s)
DICPCO2 | 1 |SM P M1 |atm |Partial Pressure of CO2 (atm)
DICPHAV | 1 |SM P M1 |dimensionless |pH (dimensionless)
8.7.1.4. Do’s and Don’ts¶
The pkg ptracer is required with use with this pkg. Also, as usual, the runtime flag useGCHEM must be set to .TRUE. in data.pkg. By itself, gchem pkg will read in data.gchem and will write out gchem diagnostics. It requires tracer experiment specific calls to do anything else (for instance the calls to dic and cfc pkgs).
8.7.1.5. Reference Material¶
8.7.1.6. Experiments and tutorials that use gchem¶
Global Ocean biogeochemical tutorial, in tutorial_global_oce_biogeo verification directory, described in section [sec:eg-biogeochem_tutorial] uses gchem and dic
Global Ocean cfc tutorial, in tutorial_cfc_offline verification directory, uses gchem and cfc (and offline) described in [sec:eg-offline-cfc]
Global Ocean online cfc example in cfc_example verification directory, uses gchem and cfc