2.1. The run sequence

This page documents the contents of a run sequence — what each kind of line means and how to read one. For what a run sequence is and how it fits into a coupled run, see Core concepts.

The run sequence is a free-format ascii file which the NUOPC driver ingests at start-up (via NUOPC_DriverIngestRunSequence).

For CESM/NorESM this is stored in the nuopc.runseq file. This file is generated by the CIME case-control system from the coupling intervals you configure; the generator lives in cime_config/runseq/ and is CIME-only (see Configuring and running a case (CESM/NorESM)).

For UFS this is stored in the runSeq file.

2.1.1. Anatomy of a run sequence

The run-sequence format below is the common NUOPC run-sequence format, whichever host ingests it.

A run sequence is delimited by runSeq:: and a closing ::. Between them, four kinds of line appear:

Time-loop markers — @<dt> … @

A line beginning with @ followed by a number opens a time loop whose period is <dt> seconds; a line with a bare @ closes the innermost open loop. Loops nest: an outer @<dt> typically wraps components coupled less frequently (for example land-ice, river, ocean), and the inner-most loop wraps the components coupled most frequently (for example atmosphere, land, sea ice). Everything between an opening @<dt> and its matching @ executes once per <dt> interval.

A doubled @@<dt> … @@ opens and closes a nested time loop in the same way; the doubled form is used to introduce an additional nesting level within a surrounding loop — for example to accumulate a field every fast interval but average it and send it to a component only on that component’s (coarser) coupling interval.

Mediator phase calls — MED <phase>

A line MED <phase> runs the registered CMEPS phase named <phase> at that point in the sequence. These names are exactly the mediator phases described in the architecture and Developer guides — for example med_phases_prep_ocn_accum, med_phases_aofluxes_run, med_phases_post_atm.

Field transfers (connectors) — <SRC> -> <DST> :remapMethod=<method>

A line such as MED -> OCN :remapMethod=redist is a connector: it transfers the connected fields from the source to the destination — here from the mediator’s export state to the ocean’s import state — using the given remap method. ATM -> MED, MED -> ATM and the like move fields into and out of the mediator.

Component runs — <COMP>

A bare component name such as ATM, OCN, ICE advances that component through one interval of the loop it sits in.

2.1.2. A worked example

The run sequence below is from a NorESM run and couples atmosphere, land, sea ice, ocean, river and land-ice at several different intervals. Read it from the outermost loop inward.

runSeq::
@86400
@10800
@3600
@1800
  MED med_phases_aofluxes_run
  MED med_phases_prep_ocn_accum
  MED med_phases_ocnalb_run
  MED med_phases_diag_ocn
@@3600
  MED med_phases_prep_ocn_avg
  MED -> OCN :remapMethod=redist
@@
  MED med_phases_prep_lnd
  MED -> LND :remapMethod=redist
  MED med_phases_prep_ice
  MED -> ICE :remapMethod=redist
  ICE
  LND
  LND -> MED :remapMethod=redist
  MED med_phases_post_lnd
  MED med_phases_diag_lnd
  MED med_phases_diag_rof
  MED med_phases_diag_ice_ice2med
  MED med_phases_diag_glc
  ICE -> MED :remapMethod=redist
  MED med_phases_post_ice
  MED med_phases_prep_atm
  MED -> ATM :remapMethod=redist
  ATM
  ATM -> MED :remapMethod=redist
  MED med_phases_post_atm
  MED med_phases_diag_atm
  MED med_phases_diag_ice_med2ice
  MED med_phases_diag_accum
  MED med_phases_diag_print
@
  OCN
  OCN -> MED :remapMethod=redist
  MED med_phases_post_ocn
@
  MED med_phases_prep_rof
  MED -> ROF :remapMethod=redist
  ROF
  ROF -> MED :remapMethod=redist
  MED med_phases_post_rof
@
  MED med_phases_prep_glc
  MED -> GLC :remapMethod=redist
  GLC
  GLC -> MED :remapMethod=redist
::

Reading this from the outside in:

  • @86400 / @10800 / @3600 / @1800 open four nested time loops with periods of one day, three hours, one hour and thirty minutes. The land-ice, river and ocean work sits in the outer loops; the fastest work — atmosphere, land and sea ice — sits in the innermost 1800-second loop.

  • Inside the fast loop, the mediator computes atmosphere/ocean fluxes and ocean albedos and accumulates the ocean forcing every 1800 s (med_phases_prep_ocn_accum).

  • The @@3600 … @@ block runs only on the ocean coupling interval: it averages the accumulated ocean forcing (med_phases_prep_ocn_avg) and transfers it to the ocean (MED -> OCN).

  • Still in the fast loop, the mediator prepares and sends land and sea-ice fields, the LND and ICE components run and return their fields, the mediator post-processes them, prepares and sends the atmosphere forcing, the ATM component runs and returns, and diagnostics are written.

  • The outer @ blocks then run the ocean, river and land-ice components on their respective (coarser) intervals, each preceded by a prep_<comp> / MED -> <COMP> pair and followed by <COMP> -> MED / post_<comp>.

Note

The exact phases, components and intervals that appear in a run sequence depend on the configuration. The example above is illustrative; the run sequence in your run’s nuopc.runseq reflects the components and coupling intervals you selected.