Re: Is there a "latFlip" command?

On Sun, 14 Jun 2009, B N wrote:

> Hi. Another newbie question here.
> Does NCL have a "latFlip" command? I see lonFlip.
> Why? I used NCL to extract PERSIANN precipitation data from binary and
> output a netcdf file. When I look at my data in ncview its
> upside-down. I attached a picture to show this. I want to turn it
> "rightside up."
> I think I specified the Lats and Lons correctly. The README file from
> the PERSIANN data says:
> "The data is a single global grid
> 400 rows x 1440 col
> covering
> 50N to 50S latitude
> & 0 to 360 longitude
> at
> 0.25 x 0.25 deg resolution
> Units are
> mm/6hr
> with NODATA values set negative ( < 0)"
>
> Any small amount of advice would be swell. Thank you!
> Sincerely,
> Bold

Bold,

The "lonFlip" name is a little misleading. It doesn't flip the
longitude values; it actually takes longitude values that go from 0 to
360, and reorders them to go from -180 to 180.

To "flip" a set of values in NCL, you can simply use the array syntax
"::-1".

However, from your printed output below, I don't see where your lat
values are going from positive to negative.

If they were, you could do something like this:

   p = p(:,::-1,:) ; Flip the latitude dimension

This would cause the "p: values themselves to be flipped
in the middle dimension, *and* it would flip your "lat"
coordinate array.

Also, you mentioned the values were flipped inside "ncview". This
software is not part of NCL; it was developed by David Pierce of
Scripps:

    http://meteora.ucsd.edu/~pierce/ncview_home_page.html

If you are plotting your values using NCL and seeing some "flipped"
behavior, let me know. It would help to see the part of the script
where you are actually doing the plotting.

--Mary

> *********************************************************
> (Script)
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"
> setfileoption("bin","ReadByteOrder","BigEndian")
> nlat = 400 ;default latitudes in file 0.25 by 0.25 degree
> nlon = 1440 ;default longitutdes in file 0.25 by 0.25 degree
> fils = systemfunc("ls raw6hr06*.bin")
> nfils = dimsizes(fils)
> prate = new((/nfils,nlat,nlon/),"float") ; New array for rain
> rate
> p = new((/nfils,nlat,nlon/),"float") ; New array for rain
> do gg = 0,dimsizes(fils)-1 ; Do loop to extract variable
> form binary files
> prate(gg,:,:) = fbindirread(fils(gg),0,(/nlat,nlon/),"float")
> p(gg,:,:) = fbindirread(fils(gg),0,(/nlat,nlon/),"float") * 3 ; rain
> per three hours (mm)
> end do
> prate = where(prate.lt.0.01 , 0.0, prate) ; keep precipitation
> values above zero
> p = where(p.lt.0.01,0.0,p) ;
> ;;;;;Assign Coordinate Variable Information;;;;;;;;;;
> print("Assigning coordinate variable information")
> lat = ispan(0,nlat-1,1)*0.25 - 49.875 ;PERSIANN DATA I think.....?
> lat_at_units = "degrees_north"
> lon = ispan(0,nlon-1,1)*0.25 - 179.875
> lon_at_units = "degrees_east"
> prate!0 = "time"
> prate&time = ispan(1,dimsizes(fils),1)
> prate!1 = "lat"
> prate&lat = lat
> prate!2 = "lon"
> prate&lon = lon
> p!0 = "time"
> p&time = ispan(1,dimsizes(fils),1)
> p!1 = "lat"
> p&lat = lat
> p!2 = "lon"
> p&lon = lon
> printVarSummary(prate)
> printMinMax(prate,True)
> printVarSummary(p)
> printMinMax(p,True)
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> print("Now try for subregion:")
> R1 = prate(:,{5:11},{-30:-20})
> R2 = prate(:,{7:18},{-20:-10})
> R3 = prate(:,{7:18},{-10:10})
> R4 = prate(:,{7:18},{10:30})
> printVarSummary(R1)
> printVarSummary(R2)
> printVarSummary(R3)
> printVarSummary(R4)
>
> ;===========REGRID at 0.50 degree========
> NLAT = 200 ; 400/2
> MLON = 720; 1440/2
> LAT = ispan(0,NLAT-1,1)*0.50 - 49.875; "0.50" degrees
> LON= ispan(0,MLON-1,1)*0.50 - 179.875; "0.50" degrees
> LAT!0 = "lat"
> LAT_at_units = "degrees_north"
> LAT&lat = LAT
> LON!0 = "lon"
> LON_at_units = "degrees_east"
> LON&lon = LON
> prate_po = area_hi2lores_Wrap (prate&lon,prate&lat, prate, True, 1,
> LON, LAT, False)
> printVarSummary(prate_po)
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> ; Output regridded data
> rm= systemfunc("rm PERSIANN_SOP3_0.50x0.50_res_6hr.nc") ;remove the
> file we are about to create
> b = addfile("PERSIANN_SOP3_0.50x0.50_res_6hr.nc","c")
> b_at_title = "1 month of daily accumulated precipitation"
> filedimdef(b,"time",-1,True) ; make time an UNLIMITED dimension,
> always recommended
> b->precipitation_rate=prate_po
> b->lat = LAT
> b->lon = LON
> ;==========Free up memory
> delete(prate)
> delete(prate_po)
> ;==========
> p_po = area_hi2lores_Wrap (p&lon,p&lat, p, True, 1, LON, LAT, False)
> printVarSummary(p_po)
> b->precipitation=p_po
> delete(p)
> delete(p_po)
> print("Finished!")
>
>
> *********terminal history
>
> mongol:2006_09_PERS6hr gkhan$ ncl extract_PERSIANN_regrid_plot-SOP3.ncl
> Copyright (C) 1995-2009 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 5.1.0
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ for more details.
> (0) Assigning coordinate variable information
>
>
> Variable: prate
> Type: float
> Total Size: 276480000 bytes
> 69120000 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 400] x [lon | 1440]
> Coordinates:
> time: [1..120]
> lat: [-49.875..49.875]
> lon: [-179.875..179.875]
> Number Of Attributes: 1
> _FillValue : -999
> (0)
> (0) min=0 max=101.596
>
>
> Variable: p
> Type: float
> Total Size: 276480000 bytes
> 69120000 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 400] x [lon | 1440]
> Coordinates:
> time: [1..120]
> lat: [-49.875..49.875]
> lon: [-179.875..179.875]
> Number Of Attributes: 1
> _FillValue : -999
> (0)
> (0) min=0 max=304.789
> (0) Now try for subregion:
>
>
> Variable: R1
> Type: float
> Total Size: 460800 bytes
> 115200 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 24] x [lon | 40]
> Coordinates:
> time: [1..120]
> lat: [5.125..10.875]
> lon: [-29.875..-20.125]
> Number Of Attributes: 1
> _FillValue : -999
>
>
> Variable: R2
> Type: float
> Total Size: 844800 bytes
> 211200 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 44] x [lon | 40]
> Coordinates:
> time: [1..120]
> lat: [7.125..17.875]
> lon: [-19.875..-10.125]
> Number Of Attributes: 1
> _FillValue : -999
>
>
> Variable: R3
> Type: float
> Total Size: 1689600 bytes
> 422400 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 44] x [lon | 80]
> Coordinates:
> time: [1..120]
> lat: [7.125..17.875]
> lon: [-9.875..9.875]
> Number Of Attributes: 1
> _FillValue : -999
>
>
> Variable: R4
> Type: float
> Total Size: 1689600 bytes
> 422400 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 44] x [lon | 80]
> Coordinates:
> time: [1..120]
> lat: [7.125..17.875]
> lon: [10.125..29.875]
> Number Of Attributes: 1
> _FillValue : -999
>
>
> Variable: prate_po
> Type: float
> Total Size: 69120000 bytes
> 17280000 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 200] x [lon | 720]
> Coordinates:
> time: [1..120]
> lat: [-49.875..49.625]
> lon: [-179.875..179.625]
> Number Of Attributes: 1
> _FillValue : -999
>
>
> Variable: p_po
> Type: float
> Total Size: 69120000 bytes
> 17280000 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 120] x [lat | 200] x [lon | 720]
> Coordinates:
> time: [1..120]
> lat: [-49.875..49.625]
> lon: [-179.875..179.625]
> Number Of Attributes: 1
> _FillValue : -999
> (0) Finished!
>
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Received on Mon Jun 15 2009 - 08:32:59 MDT