Re: Is there a function to calculate the advection?

> I am wondering if there is a function, built-in or contributed,
> which can be used to calculate the advection of a given
> variable, like ECMWF or NCEP temperature, in NCL?

I assume you mean:

        u*(dT/dx) + v*(dT/dy)

---
If the data are global then use spherical harmonic functions
to compute the gradients.
gaussian grid:
http://www.ncl.ucar.edu/Document/Functions/Built-in/gradsg.shtml
regular [fixed] grid:
http://www.ncl.ucar.edu/Document/Functions/Built-in/gradsf.shtml
---
If the grid has missing data or is limited area then
you can use "center_finite_dif" if you have a regular grid.
The grid points need not be equally spaced.
http://www.ncl.ucar.edu/Document/Functions/Built-in/center_finite_diff.shtml
Example 6 shows how to compute dT/dx ; you can use the same process for
latitude dT/dy.
---
Godd luck
D
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