Home Contact Us Site Map  
 
       
    next up previous contents
Next: 6.3.3 PTRACERS Package Up: 6.3 General purpose numerical Previous: 6.3.1 OBCS: Open boundary   Contents

Subsections


6.3.2 RBCS Package

6.3.2.1 Introduction

A package which provides the flexibility to relax fields (temperature, salinity, ptracers) in any 3-D location: so could be used as a sponge layer, or as a "source" anywhere in the domain.

For a tracer ($ T$ ) at every grid point the tendency is modified so that:

$\displaystyle \frac{dT}{dt}=\frac{dT}{dt} - \frac{M_{rbc}}{\tau_T} (T-T_{rbc}) $

where $ M_{rbc}$ is a 3-D mask (no time dependence) with values between 0 and 1. Where $ M_{rbc}$ is 1, relaxing timescale is $ 1/\tau_T$ . Where it is 0 there is no relaxing. The value relaxed to is a 3-D (potentially varying in time) field given by $ T_{rbc}$ .

A seperate mask can be used for T,S and ptracers and each of these can be relaxed or not and can have its own timescale $ \tau_T$ . These are set in data.rbcs (see below).

6.3.2.2 Key subroutines and parameters

The only change need in the code might be in RBCS.H, for PARAMETER(maskLEN = 3 ), if you need more than 3 masks (see below).



There are runtime parameters set in data.rbcs:
These runtime options include
Set in RBCS_PARM01:
$ \bullet$ Parameters to set the timing for periodic fields to relax to are to be loaded are: rbcs_ForcingPeriod, rbcs_ForcingCycle. The former is how often to load, the latter is how often to cycle through those fields (eg. period couple be monthly and cycle one year). rbcs_ForcingCycle=0 meaning no periodic forcing, and the relax field is only read in at the beginning of the run and kept constant the rest of the run. Default is 0.
$ \bullet$ rbcsIniter: if you want to offset rbcs forcing timing. Default is nIter0.
$ \bullet$ useRBCtemp: true or false (default false)
$ \bullet$ useRBCsalt: true or false (default false)
$ \bullet$ useRBCptracers: true or false (default false), must be using ptracers to set true
$ \bullet$ tauRelaxT: timescale in seconds of relaxing in temperature ($ \tau_T$ in equation above). Where mask is 1, relax rate will be 1/tauRelaxT. Default is 1. $ \bullet$ tauRelaxS: same for salinity. $ \bullet$ relaxMaskFile(irbc): filename of 3-D file with mask ($ M_{rbc}$ in equation above. Need a file for each irbc. 1=temperature, 2=salinity, 3=ptracer01, 4=ptracer02 etc. If the mask numbers end (see maskLEN) are less than the number tracers, then relaxMaskFile(maskLEN) is used for all remaining ptracers.
$ \bullet$ relaxTFile: name of file where temperatures that need to be realxed to ($ T_{rbc}$ in equation above) are stored. Need 3-D fields to match model domain, and as many entries as given by rbcsForcingPeriod and rbcsForcingCycle.
$ \bullet$ relaxSFile: same for salinity.



Set in RBCS_PARM02 for each of the ptracers (iTrc):
$ \bullet$ useRBCptrnum(iTrc): true or false (default is false).
$ \bullet$ tauRelaxPTR(iTrc): relax timescale.
$ \bullet$ relaxPtracerFile(iTrc): file with relax fields.

6.3.2.3 Do's and Don'ts

6.3.2.4 Reference Material


6.3.2.5 Experiments and tutorials that use rbcs

next up previous contents
Next: 6.3.3 PTRACERS Package Up: 6.3 General purpose numerical Previous: 6.3.1 OBCS: Open boundary   Contents
mitgcm-support@mitgcm.org
Copyright © 2006 Massachusetts Institute of Technology Last update 2011-01-09