[ncl-talk] plotting model output where x/y are not lat/lon
Will Hobbs
Will.Hobbs at utas.edu.au
Fri Aug 28 15:38:42 MDT 2015
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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