From: Tom Kilpatrick <thomaski_at_nyahnyahspammersnyahnyah>

Date: Mon Mar 28 2011 - 03:33:39 MDT

Date: Mon Mar 28 2011 - 03:33:39 MDT

(NOTE: I also sent this to wrfhelp@ucar.edu)

I have a question about computing the divergence and curl of 2D vector

fields (eg low-level winds) on the WRF lambert grid. After reading a bit of

Haltiner & Williams 1980 I am wondering if the following is correct. For

a horizontal vector field with components (A,B) in the x- and y-directions

on the lambert grid, then the divergence is given by

m^2 * [ d/dx(A/m) + d/dy(B/m) ]

and the curl is

m^2 * [ d/dx(B/m) - d/dy(A/m) ],

where m is the map factor. The above formulae could be used to compute the

divergence at the theta (mass) points and the curl at the '+' pts on the

C-grid:

th u th

v + v

th u th

One could then average the '+' pts to get the curl at the interior mass-pts.

If the above is correct it might be helpful if there were built-in NCL

functions to do this. My apologies if there already are, but I couldn't find

anything on the site, and searching through the ncl-talk archives, it looks

other users have similar questions. Note that uv2dv_cfd, uv2vr_cfd don't

work for the lambert grid.

Thanks,

Tom Kilpatrick

-- Thomas Kilpatrick, M.S. Graduate assistant thomaski@hawaii.edu Department of Oceanography University of Hawaii 1000 Pope Rd Honolulu, HI 96822

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Received on Mon Mar 28 03:33:45 2011

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