tsaving-time-series.rst - pism - [fork] customized build of PISM, the parallel ice sheet model (tillflux branch)
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tsaving-time-series.rst (4991B)
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1 .. include:: ../../global.txt
2
3 .. _sec-saving-time-series:
4
5 Saving time series of scalar diagnostic quantities
6 --------------------------------------------------
7
8 It is also possible to save time-series of certain scalar diagnostic quantities using a
9 combination of the options ``-ts_file``, ``-ts_times``, and ``-ts_vars``. For example,
10
11 .. code-block:: none
12
13 pismr -i foo.nc -y 1e4 -o output.nc -ts_file time-series.nc \
14 -ts_times 0:1:1e4 -ts_vars ice_volume_glacierized,ice_area_glacierized_grounded
15
16
17 will run for 10000 years, saving total ice volume and grounded ice area to
18 ``time-series.nc`` *yearly*. See tables :numref:`tab-time-series-opts` for the list of
19 options and :ref:`sec-ts_vars` for the full list of supported time-series.
20
21 Note that, similarly to the snapshot-saving code (section :ref:`sec-snapshots`), this
22 mechanism does not affect adaptive time-stepping. Here, however, PISM will save exactly
23 the number of time-series records requested.
24
25 Omitting the ``-ts_vars`` option makes PISM save *all* available variables listed in
26 :ref:`sec-ts_vars`. Because scalar time-series take minimal storage space, compared to
27 spatially-varying data, this is usually a reasonable choice. Run PISM with the
28 :opt:`-list_diagnostics` option to see the list of all available time-series.
29
30 If the file ``foo.nc``, specified by ``-ts_file foo.nc``, already exists then by default
31 the existing file will be moved to ``foo.nc~`` and the new time series will go into
32 ``foo.nc``. To append the time series onto the end of the existing file, use option
33 ``-ts_append``.
34
35 PISM buffers time-series data and writes it at the end of the run, once 10000 values are
36 stored, or when an ``-extra_file`` is saved, whichever comes first. Sending an ``USR1``
37 (or ``USR2``) signal to a PISM process flushes these buffers, making it possible to
38 monitor the run. (See section :ref:`sec-signal` for more about PISM's signal handling.)
39
40 .. list-table:: Command-line options controlling saving scalar time-series
41 :name: tab-time-series-opts
42 :header-rows: 1
43 :widths: 1,3
44
45 * - Option
46 - Description
47
48 * - :opt:`-ts_file`
49 - Specifies the file to save to.
50
51 * - :opt:`-ts_times`
52 - Specifies times to save at as a MATLAB-style range :math:`a:\Delta t:b`, a
53 comma-separated list, or a keyword (``hourly``, ``daily``, ``monthly``,
54 ``yearly``). See section :ref:`sec-saving-diagnostics`.
55
56 * - :opt:`-ts_vars`
57 - Comma-separated list of variables. Omitting this option is equivalent to listing
58 the *all* variables.
59
60 * - :opt:`-ts_append`
61 - Append time series to file if it already exists. No effect if file does not yet
62 exist.
63
64 Besides the above information on usage, here are comments on the physical significance of
65 several scalar diagnostics:
66
67 - For each variable named ``..._flux``, positive values mean ice sheet mass gain.
68
69 - PISM reports ice volume, ice mass, and several other quantities for "glacierized" areas.
70 These quantities do not include contributions from areas where the ice thickness is
71 equal to or below the value of the configuration parameter
72 ``output.ice_free_thickness_standard`` (in meters). Corresponding quantities without the
73 suffix *do* include areas with a thin, "seasonal" ice cover.
74
75 - Ice volume and area are computed and then split among floating and grounded portions:
76 ``ice_volume_glacierized`` :math:`\mapsto` (``ice_volume_glacierized_shelf``,
77 ``ice_volume_glacierized_grounded``) while ``ice_area_glacierized`` :math:`\mapsto`
78 (``ice_area_glacierized_shelf``, ``ice_area_glacierized_grounded``). The volumes have units
79 :math:`m^3` and the areas have units :math:`m^2`.
80
81 - The thermodynamic state of the ice sheet can be assessed, in part, by the amount of cold
82 or temperate ("``temp``") ice. Thus there is another splitting: ``ice_volume_glacierized``
83 :math:`\mapsto` (``ice_volume_glacierized_cold``, ``ice_volume_glacierized_temperate``) and
84 ``ice_area_glacierized`` :math:`\mapsto`
85 (``ice_area_glacierized_cold_base``, ``ice_area_glacierized_temperate_base``).
86
87 - The sea level rise potential :var:`sea_level_rise_potential` is the increase in sea
88 level (in meters) that would result from melting all the grounded ice not displacing sea
89 water and distributing the corresponding *fresh water* volume uniformly over the entire
90 global ocean (:math:`362.5 \cdot 10^6\, km^2`, see :cite:`Cogley2011`). This follows the
91 definition used in the SeaRISE project :cite:`Bindschadler2013SeaRISE`.
92
93 - Fields ``max_diffusivity`` and ``max_hor_vel`` relate to PISM time-stepping. These
94 quantities appear in per-time-step form in the standard output from PISM (i.e. at
95 default verbosity). ``max_diffusivity`` determines the length of the mass continuity
96 sub-steps for the SIA stress balance (sub-)model. ``max_hor_vel`` determines the
97 CFL-type restriction for mass continuity and conservation of energy contributions of the
98 SSA stress balance (i.e. sliding) velocity.