Documentation for PISM, the Parallel Ice Sheet Model

PISM stable0.4 is released

PISM version stable0.4 is available. See the stable version page to check out a copy of the source code or download an Ubuntu package. Send email to help@pism-docs.org for help with any version of PISM.

Changes (compared to stable0.3) include

Model changes

  • Merging with PISM-PIK:
    • SIA and SSA ice velocities are hybridized using simpler technique (Winkelmann et al. 2011).
    • Mass continuity finite difference scheme is conserving (Winkelmann et al. 2011).
    • Mass fluxes at calving fronts are accounted by subgrid scheme (Albrechts et al. 2011).
    • Calving model based on principle strain rates (“eigencalving”; Winkelmann et al. 2011).
  • Improved enthalpy code (Aschwanden et al. 2011).
  • In stable0.3 and 0.2, stored basal water was diffused in the horizontal (Bueler & Brown, 2009). This regularization has been removed. Instead water is stored locally and drains at a fixed, configurable rate. Users/developers are encouraged to propose and implement alternative subglacial hydrology models.
  • Implemented the bed roughness parameterization for SIA described by (Schoof, 2003).
  • PDD code computes accumulation from precipitation and a temperature threshold.
  • Temperature, precipitation, surface mass balance lapse rate corrections can modify surface inputs.

Usability improvements/changes

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  • PISM stable0.4 requires PETSc version 3.0 or 3.1. (Version 2.3.3 is not supported.)
  • New CMake-based build system.
  • Forcing by time- and space-dependent climate or surface boundary conditions: improved interface.
  • Simplified flow-line modeling using PISM. See Storglaciaren example in the User's Manual (or see the worked-storglaciaren page for a preview).
  • On Debian and Ubuntu systems PISM can be installed from a .deb package. Download it here. This is no longer the case.
  • Building development version of PISM on Debian systems is easier with the help of a meta-package depending on all necessary tools and libraries; see dev version page.
  • Model state is backed-up every wall-clock hour to make it easier to re-start interrupted runs.
  • PDD code reports melt, accumulation and runoff.
  • Updated documentation, including User's Manual, Installation Manual, and Source Code Browser.

Under the hood

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  • Better software tests.
  • Less restrictive input file format means easier to create a PISM-readable NetCDF file.
  • Improved file output performance and choice of variable order.
  • Many structural improvements:
    • re-factored stress balance code
    • re-factored flow laws
    • well-defined climate forcing
    • well-defined “diagnostic” computations
    • isolated bedrock thermal layer model, with clear interface
  • More flexible climate forcing using scalar temperature offsets
  • Clearly-identified ice surface inputs will accept output from a snow/firn model.

Experimental features

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  • Finite-element-based SSA solver.
    • Designed for use with inverse modeling codes that are not a part of this release.
  • Preliminary regional (outlet glacier) modeling support.
  • Mostly untested coupling to external energy balance/surface mass balance models.
news/stable0.4.txt · Last modified: 2012/05/03 15:00 by Constantine Khroulev
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