Form the inverse of the background error covariance matrix.
s = divand_background(mask,pmn,Labs,alpha,moddim)
Form the inverse of the background error covariance matrix with
finite-difference operators on a curvilinear grid
Input:
mask: binary mask delimiting the domain. 1 is inside and 0 outside.
For oceanographic application, this is the land-sea mask.
pmn: scale factor of the grid.
Labs: correlation length
alpha: a dimensional coefficients for norm, gradient, laplacian,...
alpha is usually [1 2 1].
Output:
s: stucture containing
s.iB: inverse of the background error covariance
s.L: spatial average correlation length
s.n: number of dimenions
s.coeff: scaling coefficient such that the background variance
diag(inv(iB)) is one far away from the boundary.
Package: divand
