Choosing proper ISTART
ISTART controls how the model first picks up the initial
conditions to start the run. We have a number of options depending on
how much information is already available.
Please note that if you get this wrong i.e. you use an ISTART that is
not compatible with the AIC, GIC or OIC files in the rundeck, the
model is not guaranteed to crash nicely. In fact, the opposite is
likely. Strange crashes on start up are very often related to this.
For more information about preserving continuity of prognostic variables
(including tracers) on ISTART=8 setups, please see:
- ISTART=1 Default start. This sets atmospheric
variables to constants and requires input files for ground values (a
GIC file), and ocean values (OIC) if required.
- ISTART=2 Observed start. This sets atmospheric
values to observations, based on a particular format of AIC file. As
for ISTART=1, input files are required for ground and ocean variables.
- ISTART=3 Not used.
- ISTART=4 A restart from an rsf file from a
previous run, but the ocean is reinitialised. Needs an initial OIC
file (for fully coupled models).
- ISTART=5 A restart from an rsf file from a
previous run, but no tracers. This is only useful for tracer runs that
need to be initialised with a particular model state.
- ISTART=6 A restart from an rsf file from a
previous run that might not have had the same land-ocean mask. This
makes sure to reset snow values, pbl values and ocean values
- ISTART=7 A restart from an rsf file from a
previous run with the same land-ocean mask. This still makes sure to
set snow values and ocean values. This is used mainly for converted
model II' data.
- ISTART=8 This is a restart from a model
configuration identical to the run now starting. This is for
perturbation experiments etc. See note below.
- ISTART=9 This is a restart from this model
run. (i.e. a continuation, or a backtrack to an older rsf file).
- ISTART=10 This is used internally to pick up
from the instantaneous rsf file (the later of fort.1 and fort.2). Does
not ever need to be set in the rundeck.
- ISTART=11 This is used internally to pick up
from an instantaneous rsf file (fort.1). Only rarely used.
- ISTART=12 This is used internally to pick up
from an instantaneous rsf file (fort.2). Only rarely used.
- ISTART=13 This is used internally to pick up
from the instantaneous rsf file (the earlier of fort.1 and
fort.2). Only rarely used.
- ISTART<0 This option is used by the
post-processing program to run the model to generate nice
diagnostics. This should never need to be set manually.