Re: storm density

From: Adam Phillips <asphilli_at_nyahnyahspammersnyahnyah>
Date: Thu Oct 03 2013 - 09:49:45 MDT

Hi Alexander,
I didn't see any replies on this, so I thought I would add the following:
1 - I believe my coding is working as intended, but due to the fact that
the grid points get smaller in area the closer you get to the poles,
this results in less counts per grid box the closer you get to the poles
due to the diminished area. Thus, if you were to combine the near-pole
grid boxes into one box similar in size to the lower latitude grid boxes
I think you would find comparable numbers.
2 - Again due to very small grid boxes near the poles, your screen
and/or NCL is possibly not resolving the tiny grid boxes near the pole.
This may result in white areas as you see. I am not 100% sure on this
point though.

A possible solution to all of this is to manually set your arr&lat array
to get more course closer to the poles. Note though that there's not
much that you can do about the convergence of the longitudes.. An example:
arr = new((/14,90/),integer,-999)
arr&lat = (/54,56,58,60,62,64,66,68,70,74,78,82,86,90/)
arr&lon = ispan(0,356,4)

If that does not produce desirable results, then counting things up on a
grid where the grid box size is the same (such as the EASE grid) would
be my next recommendation. I do not have any experience doing this and
thus someone else would need to provide guidance on how to pursue this
Hope that helps,

On 09/28/2013 11:13 AM, Alexander Semenov wrote:
> Hi ncl-talk,
> I am trying to calculate and subsequently plot the number of cyclones
> per grid cell in
> the Arctic Ocean domain based on the data from the ascii file
> (all_sum_ens1.asc). A while ago, Adam Phillips suggested the approach
> to calculate the number of storms and although the code compiled, I
> believe that the pattern of cyclone density was wrong, particularly
> over the Central Arctic. In the attached plot, you can see that the
> cyclone density over the Central Arctic is close to 0 which is too
> low. I was hoping you could suggest another approach to calculate the
> number of storms (density)
> passing each grid cell?
> Adam Phillips suggested to calculate density by setting "arr" array:
> arr = new((/100,110/),integer,-999)
> arr!0 = "lat"
> arr&lat = fspan(53.82,90,100)
> arr&lat@units = "degrees_north"
> arr!1 = "lon"
> arr&lon = fspan(0,358.9,110)
> arr&lon@units = "degrees_east"
> printVarSummary(arr)
> arr = 0 ; set array to all 0's
> do gg = 0,dimsizes(slp)-1
> if (.not.ismissing(lat(gg)).and..not.ismissing(lon(gg))) then ;
> check to make sure lat/lons are present
> arr({lat(gg)},{lon(gg)}) = (/ arr({lat(gg)},{lon(gg)})+1 /)
> end if
> Attached you will find the code and plot.
> The data file (ascii) is on your ftp server under name all_sum_ens3.asc.
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Adam Phillips                      
NCAR/Climate and Global Dynamics Division       (303) 497-1726
P.O. Box 3000				
Boulder, CO 80307-3000

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Received on Thu Oct 3 09:49:54 2013

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