[ncl-talk] plotting model output where x/y are not lat/lon
Dennis Shea
shea at ucar.edu
Fri Aug 28 15:54:00 MDT 2015
Will's suggestion is correct.
-----
FYI: The ***only*** time you should assign the reserved attributes:
@lat2d, @lon2d is for plotting.
In fact, the NCL-team would prefer that people use the following
rather than the reserved attributes.
res at sfXArraya = lon2d
res at sfYArray = lat2d
res at trGridType = "TriangularMesh"
---
Each variable having an associated @lat2d, @lon2d takes up memory.
If 5 variables a, a at lat2d, a at lon2d, ... b, c, d, e then each will
require the necessary memory.
Firther, if you write to netCDF via
fnc->A = a
fnc->B = b
fnc->C = c
fnc->D = d
fnc->E = e
Then the lat2d/lon2d arrays will be written 5 times (one for each variable).
fnc->LAT2D = lat2d
fnc->LON2D = lon2d
Will write each variable only once!
Cheers
On Fri, Aug 28, 2015 at 3:38 PM, Will Hobbs <Will.Hobbs at utas.edu.au> wrote:
> Mira
>
> To keep all the attributes from 'sf'....
>
>> sf_total = sf(0,:,:) ;sf_total is now a 2-da array with all the
>>attributes and rightmost dimensions of sf
>> sf_total = dim_sum_n(sf,0)
>
> Will
>
>
>
> On 29/08/15 5:26 AM, "mberdahl at envsci.rutgers.edu"
> <mberdahl at envsci.rutgers.edu> wrote:
>
>>Excellent, this worked! Thank you!
>>I just have a quick follow-up question. Once I assign the lat and lon to
>>my variables (for example: sf at lon2d = lon2d, sf at lat2d = lat2d), and then
>>I would like to do a calculation with sf (eg. sf_total = dim_sum_n(sf,0)),
>>it seems I have to assign the the new variable the lat and lon again. Is
>>there a way to keep the lat and lon following through the calculations
>>without always reassigning them?
>>I hope that makes sense.
>>Thanks,
>>Mira
>>
>>
>>
>>
>>> 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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