pism::stressbalance::BedSmoother Class Reference

PISM bed smoother, plus bed roughness parameterization, based on Schoof (2003). More...

#include <BedSmoother.hh>

Public Member Functions
	BedSmoother (std::shared_ptr< const Grid > g)
virtual	~BedSmoother ()=default
void	preprocess_bed (const array::Scalar &topg)
void	smoothed_thk (const array::Scalar &usurf, const array::Scalar &thk, const array::CellType2 &mask, array::Scalar &thksmooth) const
	Computes a smoothed thickness map. More...
void	theta (const array::Scalar &usurf, array::Scalar &result) const
const array::Scalar &	smoothed_bed () const

Protected Member Functions
void	preprocess_bed (const array::Scalar &topg, unsigned int Nx_in, unsigned int Ny_in)
void	smooth_the_bed_on_proc0 ()
	Computes the smoothed bed by a simple average over a rectangle of grid points. More...
void	compute_coefficients_on_proc0 ()

Protected Attributes
std::shared_ptr< const Grid >	m_grid
const Config::ConstPtr	m_config
array::Scalar2	m_topgsmooth
	smoothed bed elevation; set by calling preprocess_bed() More...
array::Scalar2	m_maxtl
array::Scalar2	m_C2
array::Scalar2	m_C3
array::Scalar2	m_C4
int	m_Nx
int	m_Ny
double	m_Glen_exponent
double	m_smoothing_range
std::shared_ptr< petsc::Vec >	m_topgp0
	original bed elevation on processor 0 More...
std::shared_ptr< petsc::Vec >	m_topgsmoothp0
	smoothed bed elevation on processor 0 More...
std::shared_ptr< petsc::Vec >	m_maxtlp0
	maximum elevation at (i,j) of local topography (nearby patch) More...
std::shared_ptr< petsc::Vec >	m_C2p0
std::shared_ptr< petsc::Vec >	m_C3p0
std::shared_ptr< petsc::Vec >	m_C4p0

Detailed Description

PISM bed smoother, plus bed roughness parameterization, based on Schoof (2003).

This class both smooths the bed and computes coefficients for an approximation to Schoof's \(\theta\). The factor \(0\le \theta \le 1\) multiplies the diffusivity in the theory of the effect of bed roughness in the SIA by Christian Schoof (2003; The effect of basal topography on ice sheet dynamics) [Schoofbasaltopg2003].

For additional information on this class see page bedrough.

The user of this class hands BedSmoother an "original" topography, and it is preprocessed to fill the smoothed topography topgsmooth, and the coefficients in an approximation to \(\theta\). This is done by a call to preprocess_bed(). The call requires the half-width of the smoothing square (a distance in m), or the number of grid points in each direction in the smoothing rectangle, and the Glen exponent.

The call to preprocess_bed() must be repeated any time the "original" topography changes, for instance at the start of an IceModel run, or at a bed deformation step in an IceModel run.

BedSmoother then provides three major functionalities, all of which must follow the call to preprocess_bed():

1. User accesses public array::Scalar topgsmooth, the smoothed bed itself.
2. User asks get_smoothed_thk() for gridded values of the consistent smoothed version of the ice thickness, which is the thickness corresponding to a given surface elevation and the pre-computed smoothed bed.
3. User asks for gridded values of \(\theta(h,x,y)\) using get_theta().

Here is a basic example of the creation and usage of a BedSmoother instance. Note that BedSmoother will update ghosted values in topgsmooth, and other internal fields, and update them in the return fields thksmooth, theta, if asked. In IceModel::velocitySIAStaggered()

BedSmoother smoother(grid, 2);
const double n = 3.0,
lambda = 50.0e3;
ierr = smoother.preprocess_bed(topg, n, lambda); CHKERRQ(ierr);
ierr = smoother.get_smoothed_thk(usurf, thk, 1, &thksmooth); CHKERRQ(ierr);
ierr = smoother.get_theta(usurf, n, 1, &theta); CHKERRQ(ierr);

See Grid documentation for initializing grid. Note we assume topg, usurf, thk, thksmooth, and theta are all created array::Scalar instances.

Definition at line 85 of file BedSmoother.hh.

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The documentation for this class was generated from the following files:

• src/stressbalance/sia/BedSmoother.hh
• src/stressbalance/sia/BedSmoother.cc