>Does anybody have edited NCL code for compute the streamfunction on
>regional scale (for example, the output by regional model)?. If there
>is no NCL code available, did you have the related FORTRAN
>subroutines? I will greatly appreciate your help.
>
>Thanks! Actually my regional model output is on fixed grid and the "dx"
>and "dy" are equal and remain unchanged. Could you please provide me your
>subroutines of the poisson solver for cartesian coordinates? Your help is
>extremely appreciated.
>-------------
There is no built-in function for streamfunction over
a limited area. However, the following approach could be used:
Since: relative_vorticity = Laplacian[ stream_function ]
Thus: stream_function = inverse_laplacian[ relative_vorticity]
Most commonly the solution is done via successive over-relaxation.
The FISHPAK library available from netlib
has subroutines for solving this class of problem:
http://www.netlib.org/fishpack/
Note that the documentation refers to "Helmholtz equations".
The Laplacain is a special case where "lambda=0.0"
Cartesian
HWSCRT - Subroutine for solving the standard five-point
finite difference approximation to the Helmholtz
equation in cartesian coordinates
(d/dx)(du/dx) + (d/dy)(du/dy) + lambda*u = f(x,y)
using a centered finite difference grid.
Unit sphere
HWSSSP - Subroutine for solving a five-point finite difference
approximation to the Helmholtz equation in spherical
coordinates and on the surface of the unit sphere
(1/sin(theta))(d/dtheta)(sin(theta)(du/dtheta))
+ (1/sin(theta)**2)(d/dphi)(du/dphi)
+ lambda*u = f(theta,phi)
using a centered finite difference grid.
Note: the HWSSSP uses colatitude and unit sphere.
---------------
These should be easy to invoke from NCL
good luck
D
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