Scalar diagnostic quantities¶
It is also possible to save time-series of certain scalar diagnostic quantities using a
combination of the options
-ts_vars. For example,
pismr -i foo.nc -y 1e4 -o output.nc \ -ts_file time-series.nc -ts_times 0:1:1e4 \ -ts_vars ice_volume_glacierized,ice_area_glacierized_grounded
will run for 10000 years, saving total ice volume and grounded ice area to
time-series.nc yearly. See tables Parameters below for the list of
options and Scalar time-series for the full list of supported time-series.
Similarly to the snapshot-saving code (section Snapshots of the model state), this mechanism does not affect adaptive time-stepping. Here, however, PISM will save exactly the number of time-series records requested.
-ts_vars makes PISM save all available variables listed in
Scalar time-series. Because scalar time-series take minimal storage space, compared to
spatially-varying data, this is usually a reasonable choice. Run PISM with the
-list_diagnostics option to see the list of all available time-series.
If the file
foo.nc, specified by
-ts_file foo.nc, already exists then by default
the existing file will be moved to
foo.nc~ and the new time series will go into
foo.nc. To append the time series onto the end of the existing file, use option
PISM buffers time-series data and writes it at the end of the run, once 10000 values are
stored, or when an
-extra_file is saved, whichever comes first. Sending an
USR2) signal to a PISM process flushes these buffers, making it possible to
monitor the run. (See section Signals, to control a running PISM model for more about PISM’s signal handling.)
append(false) If true, append to the scalar time series output file.
buffer_size(10000) Number of scalar diagnostic time-series records to hold in memory before writing to disk. (PISM writes this many time-series records to reduce I/O costs.) Send the USR2 signal to flush time-series.
filenameName of the file to save scalar time series to. Leave empty to disable reporting scalar time-series.
timesList or range of times defining reporting time intervals.
variablesRequested scalar (time-series) diagnostics. Leave empty to save all available diagnostics.
Besides the above information on usage, here are comments on the physical significance of several scalar diagnostics:
For each variable named
..._flux, positive values mean ice sheet mass gain.
PISM reports ice volume, ice mass, and several other quantities for “glacierized” areas. These quantities do not include contributions from areas where the ice thickness is equal to or below the value of the configuration parameter
.ice_free_thickness_standard. Corresponding quantities without the suffix do include areas with a thin, “seasonal” ice cover.
Ice volume and area are computed and then split among floating and grounded portions:
The volumes have units \(m^3\) and the areas have units \(m^2\).
The thermodynamic state of the ice sheet can be assessed, in part, by the amount of cold or temperate ice. Thus there is another splitting:
The sea level rise potential
sea_level_rise_potentialis the increase in sea level (in meters) that would result from melting all the grounded ice not displacing sea water and distributing the corresponding fresh water volume uniformly over the entire global ocean (\(362.5 \cdot 10^6\, km^2\), see  and
.global_ocean_area). This follows the definition used in the SeaRISE project .
max_hor_velrelate to PISM time-stepping. These quantities appear in per-time-step form in the standard output from PISM (i.e. at default verbosity).
max_diffusivitydetermines the length of the mass continuity sub-steps for the SIA stress balance (sub-)model.
max_hor_veldetermines the CFL-type restriction for mass continuity and conservation of energy contributions of the SSA stress balance (i.e. sliding) velocity.