F. Replay Strategies within ADAS

The idea of replaying the ADAS to a given analysis is applicable to multiple circumstances. The primary situation is one of trying to obtain extra output from a cycling ADAS that has perhaps been missed when the experiment first ran. Another type of replay arises when changes being implemented in the system are not expected to affect the ensemble too drastically so that in a hybrid methodology would simply replay to ensemble to that of an existing experiment; also useful to get a first glimpse of what changes might bring to the system without having to incur the cost of running the ensemble. Other cases may represent a desire to study the consequences of changes in the aerosol analysis without bothering with direct impact to the meteorological analyses; or vice versa, when the user simply wants to replay to existing aerosol analyses without bothering about the effects of changes to aerosols due to changes in the meteorology, and finally further motivations that may arise from the creativity of every user.

Replaying hybrid ADAS to given ensemble

In recent years, the ADAS replay strategy that has been mostly exercised and found to be important in getting preliminary results from first-order testing is that of ensemble-replay. Clearly, this strategy applies to systems that run some form of hybrid ensemble-variational methodology (either 3D or 4D).

Replaying a new experiment to the existing ensemble of another is controlled by a file named atmens_replay.acq. This is a single-line file providing the templated name of the location of a existing set of ensemble background fields. Say, the user has an experiment named MYEXP and wants to replay the ensemble to that of GEOS FP f5271_fp, the acquire file atmens_replay.acq should look like

/home/dao_ops/f527_fp/run/.../archive/atmens/Y%y4/M%m2/f5271_fp.atmens_ebkg.%y4%m2%d2_%h2z.tar => MYEXP.atmens_ebkg.%y4%m2%d2_%h2z.tar

and it should be placed under FVHOME/run. Notice the redirect notation (=>) in line above responsible for the automatic rename of the external file to a name consistent with the user experiment name.

It is opportune to point out that this ensemble-replay strategy is employed in the calculation of FSOI. Since GEOS ADAS FSOI strategy involves re-running the analysis solver, the ensemble of background fields need to be made available for the analysis sensitivity run. By default, in this case, the replay is a self replay, that is, one that retrieves the ensemble from from the cycling ADAS. In the case, of setting the forward ADAS to replay to an external ensemble, it is necessary to edit the file FVHOME/asens/atmens_asens.acq and get it to be consistent with setting in FVHOME/run/atmens_replay.acq (e.g., as above). Similarly, if Standalone Analyses will be exercised within the scope of the user's experiment with the ensemble being replayed to an external analyses, the file FVHOME/anasa/atmens_replay.acq needs to equal that under FVHOME/run.

One more point on replaying the ensemble of backgrounds that might be useful to users to know is that the resolution on the ensemble is not an issue. Differences in experiment resolution and that of the replayed ensemble are automatically addressed on the fly.

Replaying 3D-ADAS

There are at least two options in this context. The first is when the user wants to exactly reproduce the cycle and results of a given experiment. The second is when wants to experiment with, say, changes to the model but relying still on a given analysis from another experiment. The first case is typical when trying to recover model diagnostic output that has been lost or left our in the original experiment. The second case is useful to test relatively mild changes to the model when these are not expected to change the analyses too drastically.

The following are the steps to replay in the scenarios just described:

1. Edit either the main job script under the FVHOME/run add the following environment settings:

setenv GAAS_ANA 0

setenv SKIPANA 1

setenv LOCAL_ACQUIRE 0

setenv aod_parallel_flag 0

be aware that some of the variables above are already defined in the main job script, that is, make sure the settings above take precedence.

2. Required acquire files:

Rename the file noreplay.acq as:

mv noreplay.acq replay.acq

This file needs to be edited and point to the desired analysis file, as in for example:

/home/dao_ops/d5271_it_sample/run/.../archive/ana/Y%y4/M%m2/d5271_it_sample.ana.eta.%y4%m2%d2_%h200z.nc4 => USREXP.ana.eta.%y4%m2%d2_%h200z.nc4

where USREXP represents the name of the user (new; replayed) experiment.

Add to FVHOME/run a file named: replay_agcm.acq and have it set as, for example:

/home/dao_ops/d5271_it_sample/run/.../archive/rs/Y%y4/M%m2/d5271_it_sample.agcm_import_rst.%y4%m2%d2_%h200z.nc4 => USREXP.agcm_import_rst.%y4%m2%d2_%h200z.nc4

This ensures the model will see the IAU forcing term from the original experiment (d5271_it_sample, in the example here).

Finally, add to FVHOME/run a file named: replay_aod.acq with contents similar to:

/home/dao_ops/d5271_it_sample/run/.../archive/chem/Y%y4/M%m2/d5271_it_sample.aod_a.sfc.%y4%m2%d2_%h200z.nc4 => USREXP.aod_a.sfc.%y4%m2%d2_%h200z.nc4

/home/dao_ops/d5271_it_sample/run/.../archive/chem/Y%y4/M%m2/d5271_it_sample.aod_f.sfc.%y4%m2%d2_%h200z.nc4 => USREXP.aod_f.sfc.%y4%m2%d2_%h200z.nc4

/home/dao_ops/d5271_it_sample/run/.../archive/chem/Y%y4/M%m2/d5271_it_sample.aod_k.sfc.%y4%m2%d2_%h200z.nc4 => USREXP.aod_k.sfc.%y4%m2%d2_%h200z.nc4

This ensures the aerosol analysis used in the original experiment is also used in the replayed experiment.

Replaying 3D-ADAS but still running AOD analysis.

A possible desirable scenario is one in which the user is testing changes to the GAAS - the aerosol analysis - component of the ADAS. Since the interaction between the atmospheric analysis and that of the aerosol analysis is very indirect, it is rather conceivable to test changes to the latter without having to take the burden of having to run the former.

This can be easily accomplished with a minor modification of the instructions above (for replaying 3D-ADAS):

1. In step (1) above, simply remove the setting:

setenv GAAS_ANA 0

the default is to have GAAS_ANA set to 1 - run it.

2. Do not place a file replay_aod.acq under FVHOME/run.