[ncl-talk] plotting model output where x/y are not lat/lon
Dave Allured - NOAA Affiliate
dave.allured at noaa.gov
Thu Aug 27 21:55:00 MDT 2015
Here is more information about dat with 2-D coordinates. I was typing this
up when I saw Will's reply. Some of the other examples indicate
that trGridTrype may not be needed with some data sets.
Please see section #2 on this documentation page, for a basic description.
Notice the several different working examples:
https://www.ncl.ucar.edu/Document/Graphics/overlays_on_map.shtml
(Please ignore the link "2D vertical coordinates", that is not about
geographic surface maps, and can be confusing.)
The simplest example for making map plots with 2-D coordinates is example 3
on this page:
https://www.ncl.ucar.edu/Applications/ice.shtml
I also like NARR example 4 because it shows how the 2-D coordinate method
can be used with different map projections:
http://www.ncl.ucar.edu/Applications/narr.shtml
--Dave
On Thu, Aug 27, 2015 at 9:35 PM, Will Hobbs <Will.Hobbs at utas.edu.au> wrote:
> Mira
>
> It looks like you have 2-d lat and lon arrays associated with your data,
> as is often the case with models (especially ocean models).
>
> This can be plotted by NCL without regridding, see the examples here:
> http://www.ncl.ucar.edu/Applications/ease.shtml
> Although you are not using the EASE grid, the principal is exactly the
> same:
>
> 1. Set your map plot grid type resource
> >res at trGridTrype = "TriangularMesh"
>
> 2. Set the lat and lon arrays as attributes of the array you are plotting,
> so if your array is 'x'
> > x at lat2d = LAT
> > x at lon2d = LON
>
> The just use one of the gsn_csm contour map plotting functions as normal.
>
> I hope that's clear.
>
> Will
>
>
> On 28/08/15 1:27 PM, "Yuqiang Zhang" <yuqiangzhang.thu at gmail.com> wrote:
>
> >Hi Mira,
> >
> >Check the link here
> >http://www.ncl.ucar.edu/FAQ/
> >For Q 27:
> >
> >When I call one of the gsn_csm_xxxx_map plotting scripts, I get an error
> >message about a units attribute not being correct.
> >If you are using one of the gsn_csm_xxx_map functions to overlay data on a
> >map, and seeing one or both of the following error messages:
> >
> > (0) is_valid_lat_ycoord: Warning: The units attribute of
> > the Y coordinate array is not set to one of the allowable
> > units values (i.e. 'degrees_north'). Your latitude labels
> > may not be correct.
> >
> > (0) is_valid_lat_xcoord: Warning: The units attribute of
> > the X coordinate array is not set to one of the allowable
> > units values (i.e. 'degrees_east'). Your longitude labels
> > may not be correct.
> >then this means that your data contains coordinate arrays, but the
> >coordinate arrays either don't have the necessary "units" attribute, or
> >it's
> >not set to one of the allowable values ("degrees_east" for longitude
> >values
> >and "degrees_north" for latitude values).
> >If your coordinate arrays are indeed degrees east and degrees north, then
> >you can set the units attribute as follows (this code snippet assumes your
> >data array is called "data" and that the coordinate arrays are called
> >"lat"
> >and "lon"):
> >
> > data&lat at units = "degrees_north"
> > data&lon at units = "degrees_east"
> >
> >Regards,
> >Yuqiang
> >
> >-----Original Message-----
> >From: ncl-talk-bounces at ucar.edu [mailto:ncl-talk-bounces at ucar.edu] On
> >Behalf
> >Of mberdahl at envsci.rutgers.edu
> >Sent: Thursday, August 27, 2015 10:21 PM
> >To: ncl-talk at ucar.edu
> >Subject: [ncl-talk] plotting model output where x/y are not lat/lon
> >
> >Hi all,
> >
> >I'm trying to make a simple plot of cumulative snowfall with data from a
> >model I did not run. When I try to make a simple plot, I receive the
> >following error:
> >
> >(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'
> >
> >
> >%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >
> >When I dump the file it looks like this:
> >
> >netcdf ICE.1983.01-12.f77 {
> >dimensions:
> > TIME = UNLIMITED ; // (365 currently)
> > X10_69 = 60 ;
> > Y18_127 = 110 ;
> > SECTOR = 2 ;
> > SECTOR1_1 = 1 ;
> > ATMLAY14_23 = 10 ;
> > bnds = 2 ;
> > ATMLAY23_23 = 1 ;
> > ATM6H3_3 = 1 ;
> > OUTLAY = 20 ;
> > OUTLAY1_1 = 1 ;
> >
> >variables:
> > double TIME(TIME) ;
> > TIME:units = "HOURS since 1901-01-15 00:00:00" ;
> > TIME:long_name = "time" ;
> > TIME:time_origin = "15-JAN-1901 00:00:00" ;
> > TIME:axis = "T" ;
> > float DATE(TIME) ;
> > DATE:units = "YYYYMMDDHH" ;
> > DATE:long_name = "Date(YYYY MM DD HH)" ;
> > DATE:history = "From ICE.f77.1983.01.01-15" ;
> > double X10_69(X10_69) ;
> > X10_69:units = "km" ;
> > X10_69:long_name = "x" ;
> > X10_69:point_spacing = "even" ;
> > X10_69:axis = "X" ;
> >
> > double Y18_127(Y18_127) ;
> > Y18_127:units = "km" ;
> > Y18_127:long_name = "y" ;
> > Y18_127:point_spacing = "even" ;
> > Y18_127:axis = "Y" ;
> > float LON(Y18_127, X10_69) ;
> > LON:units = "degrees" ;
> > LON:long_name = "Longitude" ;
> > LON:history = "From ICE.f77.1983.01.01-15" ;
> > float LAT(Y18_127, X10_69) ;
> > LAT:units = "degrees" ;
> > LAT:long_name = "Latitude" ;
> > LAT:history = "From ICE.f77.1983.01.01-15" ;
> >
> >Clearly there are lats and lons associated with the x and y spacing, but
> >I'm
> >not sure how to tell NCL how to use those. Does anyone have advice on
> >this?
> >
> >Thanks in advance,
> >Mira
>
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