[ncl-talk] Spatial filtering with a Gaussian distribution

[brianjs @iastate.edu]

Good Evening.

For my 4 km WRF runs, I am attempting to filter out waves that are
approximately less than 26 km using the spectral gaussian filter technique.
For filtering waves below 26 km at 4 km grid spacing, 13 weight seem to be
necessary. I used the filwgts_normal function to achieve a gaussian
distribution for 13 weights needed for the data smoothing and I used that
for the wgt_runave_n_Wrap function.

I have attached my code and two plots (one with filtering and one without).
Before I assume this method is correct (which it looks to be to me), I
wanted to ask a few questions. For the 3rd argument in wgt_runave_n_Wrap,
does the symmetric averaging induced by -1 simulate a normal gaussian
distribution? Also, for the normalizing of the weights (as in example 5 for
the wgt_runave_n_Wrap page), I take the square root of this value since the
filter can only be applied one dimension at a time and for doing this
across an area (lat and lon), I have to filter in one axis and then do so
again over the same points along another axis (to filter out 26 km waves in
both the x and y directions). Would this be the correct approach with the
way the filwgts_normal and runave functions work? Any input is greatly
appreciated!

Note, I could not send any WRF output files via ftp (i.e. the original file
or a significantly reduced file with only the necessary variables needed)
as I received the following error:
500 OOPS: priv_sock_get_cmd

Brian Squitieri
Graduate Research Assistant
Iowa State University
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20141030/6133f405/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: WRF_Deep_MFC_filter_2010_06_20_21.png
Type: image/png
Size: 179939 bytes
Desc: not available
Url : http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20141030/6133f405/attachment-0002.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: WRF_Deep_MFC_no_filter_2010_06_20_21.png
Type: image/png
Size: 238732 bytes
Desc: not available
Url : http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20141030/6133f405/attachment-0003.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: wrf_filtered_ambient_convergence.ncl
Type: application/octet-stream
Size: 9519 bytes
Desc: not available
Url : http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20141030/6133f405/attachment-0001.obj