[ncl-talk] Fwd: Regridding from fine to coarse resolution by aggregating not interpolating

Mon Sep 29 22:33:24 MDT 2014

Yes! It worked.

Thanks so much for your help,

Raquel

________________________________
From: Dennis Shea <shea at ucar.edu>
Sent: Tuesday, September 30, 2014 12:25 AM
To: Silva, Raquel
Cc: ncl-talk at ucar.edu; Carl Schreck
Subject: Re: [ncl-talk] Fwd: Regridding from fine to coarse resolution by aggregating not interpolating

I see the issue (I think). There must a latitude value and a longitude value for each input 'z' value. I speculate that zlat and zlon are one-dimensional while z is two-dimensional. Thus the zlat/zlon must be replicated (broadcast) to the same dimensionality as z.  Try

; Get data
     z_in = addfile(infile,"r")
     zlat  = z_in->lat
     zlon = z_in->lon
     z      = z_in->pop

     nzlat= dimsizes(zlat)
     nzlon= dimsizes(zlon)

     zlat2d = conform_dims( (/nzlat,nzlon/), zlat, 0)
     zlon2d = conform_dims( (/nzlat,nzlon/), zlon, 1)

[snip]

     bin_sum(gbin,gknt,glon,glat,ndtooned(zlon2d),
ndtooned(zlat2d),ndtooned(z) )

On Mon, Sep 29, 2014 at 9:31 PM, Silva, Raquel <rasilva at live.unc.edu<mailto:rasilva at live.unc.edu>> wrote:

Dennis,

Thanks for the references. I was able to run Example 2 and I also looked at Example 1 and compared it to my script.

If I understand it correctly, the error I get ('bin_sum: zlat must be the same size as zlon') is related with the dimensions of lon and lat in the original data not nlat and mlon:

(...)

;*****************************************************************
; Get new grid and data to regrid
;*****************************************************************

; Get new grid
  g_in = addfile(gfile,"r")
  glat = g_in->lat
  glon = g_in->lon

  nlat = dimsizes(glat)
  mlon = dimsizes(glon)

  print("New grid = "+mlon+"x"+nlat)

; Get data
  z_in = addfile(infile,"r")
  zlat = z_in->lat
  zlon = z_in->lon
  z = z_in->pop

  nlat_in = dimsizes(zlat)
  nlon_in = dimsizes(zlon)

  print("Original grid = "+nlon_in+"x"+nlat_in)
  print(" ")

  z_sum = sum(z)

  print("Sum z:")
  print(z_sum)
  print(" ")

;*****************************************************************
; Variables to hold binned quantities
;*****************************************************************
  gbin  = new ( (/nlat,mlon/), float )
  gknt  = new ( (/nlat,mlon/), integer)

  gbin  = 0.0                      ; initialization
  gknt  = 0

;*****************************************************************

; Regrid data

;*****************************************************************
  bin_sum(gbin,gknt,glon,glat,ndtooned(zlon), ndtooned(zlat),ndtooned(z) )

  z_out_sum = sum(gbin)

  print("Sum z_out:")
  print(z_out_sum)

(...)

Is there anything else I should check/change?

Thanks,
Raquel

________________________________
From: ncl-talk-bounces at ucar.edu<mailto:ncl-talk-bounces at ucar.edu> <ncl-talk-bounces at ucar.edu<mailto:ncl-talk-bounces at ucar.edu>> on behalf of Dennis Shea <shea at ucar.edu<mailto:shea at ucar.edu>>
Sent: Monday, September 29, 2014 7:30 PM
To: ncl-talk at ucar.edu<mailto:ncl-talk at ucar.edu>
Subject: [ncl-talk] Fwd: Regridding from fine to coarse resolution by aggregating not interpolating

This response was inadvertently not sent to ncl-talk at ucar.edu<mailto:ncl-talk at ucar.edu>

---------- Forwarded message ----------
From: Dennis Shea <shea at ucar.edu<mailto:shea at ucar.edu>>
Date: Mon, Sep 29, 2014 at 2:40 PM
Subject: Re: [ncl-talk] Regridding from fine to coarse resolution by aggregating not interpolating
To: "Silva, Raquel" <rasilva at live.unc.edu<mailto:rasilva at live.unc.edu>>
Cc: Carl Schreck <cjschrec at ncsu.edu<mailto:cjschrec at ncsu.edu>>

You should be able to bin.  nlat and mlon *can* be different sizes.

I just ran: Example 2  (random data):

http://www.ncl.ucar.edu/Applications/binning.shtml

You can download the script and run it. Here nlat=36 and mlon=61

===

On Mon, Sep 29, 2014 at 2:11 PM, Silva, Raquel <rasilva at live.unc.edu<mailto:rasilva at live.unc.edu>> wrote:

Hi Carl and Dennis,

Thanks for your quick responses.

I'm getting the following error:

fatal:bin_sum: zlat must be the same size as zlon

where

  zlat = z_in->lat
  zlon = z_in->lon

I thought that I could have different sizes for longitude and latitude.

Thanks,

Raquel

________________________________
From: Dennis Shea <shea at ucar.edu<mailto:shea at ucar.edu>>
Sent: Monday, September 29, 2014 4:05 PM
To: Carl Schreck
Cc: Silva, Raquel; ncl-talk at ucar.edu<mailto:ncl-talk at ucar.edu>
Subject: Re: [ncl-talk] Regridding from fine to coarse resolution by aggregating not interpolating

Also, see:

http://www.ncl.ucar.edu/Applications/

on the right under "Data Analysis", Click "Binning"

There are a few examples.

===
If you are new to NCL, pleasesee

http://www.ncl.ucar.edu/Document/Manuals/

[1] Mini-Language Manual    (concise but detailed language overview)

[2] the DKRZ tutorials. This is a rather large pdf.
     The 1st contains a subset of the Mini-Language Manual plu many examples.
     The 2nd has a lot of exercises. Unfortunately, not all the data sets are available
     for general use.

Cheers

On Mon, Sep 29, 2014 at 1:00 PM, Carl Schreck <cjschrec at ncsu.edu<mailto:cjschrec at ncsu.edu>> wrote:
Hi Raquel,

I believe bin_sum will do what you're looking for:
http://www.ncl.ucar.edu/Document/Functions/Built-in/bin_sum.shtml

    Carl

On Mon, Sep 29, 2014 at 2:25 PM, Silva, Raquel <rasilva at live.unc.edu<mailto:rasilva at live.unc.edu>> wrote:

Hi all,

I need to regrid global data from a fine (30"x30") to a coarser (0.7x0.5 deg) resolution so that each output cell contains the sum of the input cells that are encompassed by the extent of that cell. Could you please let me know if there is an ncl function I could use?

Thanks,
Raquel

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 Cyclone<http://www.cyclonecenter.org/>Center.org<http://www.cyclonecenter.org/>        Carl J. Schreck III, PhD
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North Carolina State University<http://ncsu.edu/>
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