[ncl-talk] about "check_for_y_lat_coord and valid latitude coordinate array"
Mary Haley
haley at ucar.edu
Mon Oct 26 09:46:22 MDT 2015
Liang,
The error is telling you that NCL can't find any lat/lon information
associated with your data, so it doesn't know where to put your data on the
map.
Thanks for providing a dump of your NetCDF file. It shows that you have
two-dimensional lat/lon coordinates:
float longitude ( y, x )
standard_name : longitude
long_name : longitude
units : degrees_east
_CoordinateAxisType : Lon
float latitude ( y, x )
standard_name : latitude
long_name : latitude
units : degrees_north
_CoordinateAxisType : Lat
In order to correctly plot these, you need to attach them as "lat2d" and
"lon2d" attributes to your data variable:
Instead of this:
temp = f->air_temperature (0,:,:)
lon = f->longitude (:,:)
lat = f->latitude (:,:)
timebnds = f->time_bnds
Do this:
temp = f->air_temperature (0,:,:)
temp at lon2d = f->longitude ; Note, the "(:,:)" is not needed
temp at lat2d = f->latitude
timebnds = f->time_bnds
If your data is not global, then you may also need this:
res at gsnAddCyclic = False ; don't add a longitude cyclic point
I did notice that you have these two lines commented out:
;res at sfXArray = lon
;res at sfYArray = lat
This is a second way that you can provide the lat/lon information to the
plotting routine. I usually prefer the "lat2d/lon2d" attribute method,
because gsnAddCyclic only works with this method.
I will try to come up with a "generic" page on contouring, to better
explain these various methods.
--Mary
On Mon, Oct 26, 2015 at 8:26 AM, wh.lakes.2015 <wh.lakes.2015 at gmail.com>
wrote:
>
>
> ------------------------------
> *发件人：*Si ZH <wh.lakes.2015 at gmail.com>
> *发送时间：*2015-10-25 16:36
> *主题：*about "check_for_y_lat_coord and valid latitude coordinate array"
> *收件人：*"ncl-talk"<ncl-talk at ucar.edu>
> *抄送：*
>
> Hi there,
>
> I am a new learner of UCL and was blocked at the gate of .nc file "read
> in" step. I use "ncl_filedump" and can see the dimensions and variables in
> my .nc file, but I don't know how to read those dimensions and variables
> correctly in NCL,
>
> NCL version I am using is 6.3.0, the contents of "myfile.nc" like below:
>
> $ ncl_filedump myfile.nc
> Copyright (C) 1995-2015 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 6.3.0
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ for more details.
>
> Variable: f
> Type: file
> filename: myfile
> path: myfile.nc
> file global attributes:
> CDI : Climate Data Interface version 1.6.1 (
> http://code.zmaw.de/projects/cdi)
> Conventions : CF-1.5
> history : Thu Jan 22 19:25:20 2015: cdo sub
> SM_MAM.zhyaa.pm.03236.206912-209911.nc SM_MAM.zhyaa.03236.198012-201011.nc
> zhyaa.MAM.mean.diff.2080.03236.nc
> Thu Jan 15 16:48:56 2015: cdo -timmean -selmon,3,4,5
> zhyaa.03236.monthly.198012-201011.nc SM_MAM.zhyaa.03236.198012-201011.nc
> Converted from PP by cf-python v0.9.8.3
> source : UM
> runid : zhyaa
> stash_code : 3236
> lbproc : 0
> submodel : 1
> CDO : Climate Data Operators version 1.6.1 (
> http://code.zmaw.de/projects/cdo)
> dimensions:
> x = 134
> y = 102
> time = 1 // unlimited
> nb2 = 2
> variables:
> float longitude ( y, x )
> standard_name : longitude
> long_name : longitude
> units : degrees_east
> _CoordinateAxisType : Lon
>
> float latitude ( y, x )
> standard_name : latitude
> long_name : latitude
> units : degrees_north
> _CoordinateAxisType : Lat
>
> double time ( time )
> standard_name : time
> bounds : time_bnds
> units : days since 1950-12-01 00:00:00
> calendar : 360_day
>
> double time_bnds ( time, nb2 )
> units : days since 1950-12-01 00:00:00
> calendar : 360_day
>
> float air_temperature ( time, y, x )
> standard_name : air_temperature
> long_name : TEMPERATURE AT 1.5M
> units : K
> coordinates : longitude latitude
> _FillValue : -1.073742e+09
> missing_value : -1.073742e+09
> cell_methods : time: mean
>
>
> My NCL scripts I wrote like below:
>
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>
> begin
>
> ;;;read in temp data
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>
> f = addfile("myfile.nc","r")
>
> temp = f->air_temperature (0,:,:)
> lon = f->longitude (:,:)
> lat = f->latitude (:,:)
> timebnds = f->time_bnds
>
> ;temp!0 = "time"
> ;temp!1 = "y"
> ;temp!2 = "x"
>
>
> ; temp&y at units = "degrees_north"
> ;temp&x at units = "degrees_east"
>
> ;temp = temp - 273.15
> lon = lon-180
>
> temp at units = "(C)"
>
> wks = gsn_open_wks("x11", "myfile")
>
> wks at wkWidth = 6400
> wks at wkHeight = 4000
>
> res = True ;Indicate you want to set some resources.
> res at cnFillOn = True ; Turn on contour line fill.
> ;res at cnLinesOn = False ; no contour lines.
> res at cnLevelSpacingF = 0.5 ; contour spacing.
> res at gsnSpreadColors = True ; full colors
> res at cnLineLabelsOn = False ; turn off line label.
>
> res at cnMonoFillColor = False ; Use multiple colors.
>
>
> ;res at mpMinLatF = 40
> ;res at mpMaxLatF = 50
> ;res at mpMinLonF = -92.5
> ;res at mpMaxLonF = -75.5
>
>
> res at pmLabelBarDisplayMode = "Always"
>
> res at pmLabelBarOrthogonalPosF = 0.08
>
> ;res at tiXAxisString = lon at long_name
> ;res at tiYAxisString = lat at long_name
>
> ;res at sfXArray = lon
> ;res at sfYArray = lat
>
>
> ;res at lbAutoLabelStride = True
>
> plot = gsn_csm_contour_map (wks,temp,res)
>
>
> end
>
>
> and NCL error message like below:
>
>
> (0) check_for_y_lat_coord: Warning: Data either does not contain a
> valid latitude coordinate array or doesn't contain one at all.
> (0) A valid latitude coordinate array should have a 'units' attribute
> equal to one of the following values:
> (0) 'degrees_north' 'degrees-north' 'degree_north' 'degrees north'
> 'degrees_N' 'Degrees_north' 'degree_N' 'degreeN' 'degreesN' 'deg north'
> (0) check_for_lon_coord: Warning: Data either does not contain a valid
> longitude coordinate array or doesn't contain one at all.
> (0) A valid longitude coordinate array should have a 'units' attribute
> equal to one of the following values:
> (0) 'degrees_east' 'degrees-east' 'degree_east' 'degrees east'
> 'degrees_E' 'Degrees_east' 'degree_E' 'degreeE' 'degreesE' 'deg east'
>
>
> The data in "myfile.nc" are North American Great Lakes area temperature
> contour data (the large boundary is middle and East of US and Canada, and I
> have narrowed the map latitude and longitude to Great Lakes area, but the
> results looks nothing about my data, it looks like all over the world or
> East Asian area, it is why I used lon = lon - 180). My object is to figure
> out Great lakes Area temperature contour.
>
> I think my error is like NCL message said (I didn't read in correct
> dimensions and coordinates), but I can't 100% understand "myfile.nc" via
> NCL mini manuals, and don't know how to write tha correct scripts that can
> read in "myfile.nc" (with dimensions: y, x, time and time_bnd)
>
> I attach "myfile.nc" inside the attachment, hope you can help this,
>
> Thank you,
>
> Liang Zhang
>
>
>
>
>
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