The Design Document page provides a description of the algorithms, implementation and planned testing including unit, verification, validation and performance testing. Please read Step 1.3 Performance Expectations that explains feature documentation requirements from the performance group point of view.
Design Document
In the table below, 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation, 
- completed, 
- in progress, 
- not done
Overview table for the owner and an approver of this feature
1.Description | |
| 2.Owner | Stephen Price |
| 3.Created | |
| 4.Equ | |
| 5.Ver | |
| 6.Perf | |
| 7.Val | |
| 8.Approver | |
| 9.Approved Date |
Title: O_24_LI MPAS Land Ice in ACME Design Doc
Requirements and Design
ACME Ocean and Ice Group
Date: 2015-9-23
Summary
Requirements
Requirement: Conservation of mass, energy, and momentum
Date last modified: 2015-9-23
Contributors: Stephen Price
The land ice model will conserve mass, energy, and momentum.
Requirement: Accurate marine ice sheet dynamics
Date last modified: 2015-9-23
Contributors: Stephen Price
The momentum and mass conservation components of the dynamical core will provide an accurate simulation of marine ice sheet dynamics. Specifically, the simulation of retreat and advance of the grounding line (position at which ice goes afloat due to buoyancy) will be verified according to standard benchmark test cases.
Requirement: Iceberg calving
Date last modified: 2015-9-23
Contributors: Stephen Price
The momentum and mass conservation components of the dynamical core will allow for the retreat and advance of floating ice margins (the fronts of ice shelves) through the implementation of iceberg "calving" physics.
Requirement: Support for optimal initial conditions
The initial condition for the ice sheet model should be both a good representation of present-day observations of the ice sheet state (e.g., the geometry and velocity fields) and should be approximately equilibrated with present-day forcing from the climate model (in order to avoid undesirable ice sheet model transients that could mask actual trends of interest).
Algorithmic Formulations
Design solution: N/A
Date last modified: 2015-9-23
Contributors: Stephen Price
Algorithmic formulations for all of the above requirements are discussed in their respective design documents, already published paper, or existing model documentation (referenced as appropriate in the design solutions / implementation sections below).
Design and Implementation
Implementation: Conservation of mass, energy, and momentum
Date last modified: 2015-9-23
Contributors: Stephen Price
- Conservation of energy: Conservation of energy is expressed through the advective-diffusive heat equation. Within MPAS-LI, this will be implemented largely in the form of a column-physics package copied over from the CISM2.0 model, with additional hooks to MPAS-LI advection routines. Additional detail on the heat balance in CISM2.0 can be found in the model documentation links in the References section below.
- Conservation of momentum: Conservation of momentum is expressed by the (3d) solution of the first-order accurate approximation to the Stokes equations for ice flow. Discretization of the governing nonlinear PDEs uses the finite element method on unstructured, Delaunay meshes (the dual mesh to an MPAS CVT mesh). Within MPAS-LI, the discretization and solution of the resulting linear and nonlinear systems of equations is handled by the FELIX-Albany solver, which is discussed in detail in Tezuar et al. (2015a, 2015b) in the References list below. Considerations for Including the relevant solver libraries in ACME are discussed in a separate code review document.
Implementation: Support for optimal initial conditions
Date last modified: 2015-9-23
Contributors: Stephen Price
Because of the long timescales associated with equilibrium of processes internal to ice sheets (primarily thermal equilibration), standard climate model "spin up" methods are problematic for ice sheet models in terms of providing optimal initial conditions and / or initial conditions that are in quasi-equlibrium with a given climate forcing. For a number of reasons (discussed in detail in Perego et al., 2014), these goals are best addressed through formal, adjoint-based optimization methods. A brief discussion of the approach is given in the design document here. In general, we are implementing methods pioneered under the PISCEES project and discussed in Perego et al. (2014).
Planned Verification and Unit Testing
Verification and Unit Testing: short-desciption-of-testing-here
Date last modified:
Contributors: (add your name to this list if it does not appear)
How will XXX be tested? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
Planned Validation Testing
Validation Testing: short-desciption-of-testing-here
Date last modified:
Contributors: (add your name to this list if it does not appear)
How will XXX be tested? What observational or other dataset will be used? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
Planned Performance Testing
Performance Testing: short-desciption-of-testing-here
Date last modified:
Contributors: (add your name to this list if it does not appear)
How will XXX be tested? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
References
- Perego, M., S. Price, and G. Stadler, 2014: Optimal initial conditions for coupling ice sheet models to Earth system models. … of Geophysical Research: Earth …, doi:10.1002/(ISSN)2169-9011. link
- Tezaur, I., M. Perego, A. Salinger, R. Tuminaro, and S. Price. 2015a. Albany/FELIX: a parallel, scalable and robust, finite element, first-order Stokes approximation ice sheet solver built for advanced analysis, Geophys. Model Devel., 8, doi:10.5194/gmd-8-1197-2015. link
- Tezaur, I., R. Tuminaro, M. Perego, A. Salinger, S. Price, 2015b: On the scalability of the Albany/FELIX first-order Stokes approximation ice sheet solver for large-scale simulations of the Greenland and Antarctic ice sheets", Numerical and Computational Developments to Advance Multiscale Earth System Models (MSESM)/International Conference on Computational Science (ICCS15), Reykjavik, Iceland link
- MPAS Land Ice Model User's Guide Version 3.0. link
- CISM2.0.5 Documentation link