>If i want to comput vertical velocity (w)
>anyone can help me or provide the function code for me?
You have not provided enough information.
What type of grid do you have?
What is the vertical coordinate?
What variables are available?
--- If you have divergence [D] or wind components [u,v; from which the divergence can be calculated], the simplest approach is to use the "kinematic" method if the data are on constant pressure levels.w(p) = w(p-1) + D*dp where D is the mean layer divergence.
If D is not available, it may be calculated via the NCL functions:
(a) global grids: uuv2dvF or v2dvG http://ngwww.ucar.edu/ngdoc/ng/ref/ncl/functions/uv2dvF.html (b) regional grids on regular or gaussian grids: uv2dv_cfd http://ngwww.ucar.edu/ngdoc/ng/ref/ncl/functions/vrdvcfd.html
--- The more complicated quasigeostrophic approach can also be used to estimate omega. NCL possesses all the necessary elements for doing this on global grids including inverting the laplacian.
--- good luck
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