# [ncl-talk] slice plot

Dennis Shea shea at ucar.edu
Thu Oct 2 16:10:11 MDT 2014

Some examples of what DaveB is talking about are at:

====
https://www.ncl.ucar.edu/Applications/narr.shtml
Examples 5 & 6

NARR Example 5 uses a weight file generated by an ESMF Example 30
http://www.ncl.ucar.edu/Applications/ESMF.shtml

=====
http://www.ncl.ucar.edu/Applications/asr.shtml
Examples 5 & 6

++++++++++++++++++++++++++++++++++++++++++++++++++++

http://www.ncl.ucar.edu/Document/Manuals/

[1]  The "Mini-Language Manual" contains a detailed overview of the
language

[2] THE DKRZ turotials are quite good.

On Thu, Oct 2, 2014 at 3:56 PM, David Brown <dbrown at ucar.edu> wrote:

> Hi Bedassa,
>
> You can't plot something with a 2D coordinate against a 1D coordinate in a
> 2D plot. The lon2d gives the longitude values for a horizontal 2D field.
> You have to make some choices to get a vertical plot -- you need to reduce
> the latitude dimension to a single element somehow. The simplest thing to
> do would be to just pick one index along the y axis of the lon coordinate
> -- e.g. lon2d(100,:). However, because the coordinates are 2d, the chances
> are that this would not be a constant latitude, so you could not say for
> instance that your plot represents height vs longitude at 10 degrees North
> latitude.
>
> But with proper labeling you could describe what this plot does represent.
> I suggest you look at the NCL Examples page for Pressure/Height vs
> Longitude plots and specifically at the last example on the page called
> narr_6.ncl. It shows height plots for data where the coordinates are 2D
> (aka "curvilinear" coordinates). Notice that the X axis for these plots has
> both lat/lon values for the tickmark labels.This should give you some ideas
> of what the issues are and how to solve them.
>
> Creating a plot where the latitude is constant would require a bit more
> work. But if you wanted to try you would probably want to use the function
> getind_latlon2d. This might actually be a good topic for a future example.
>  -dave
>
>
> On Wed, Oct 1, 2014 at 4:24 PM, Bedassa Regassa <beregassa at gmail.com>
> wrote:
>
>> I am new to ncl. I am to plot the vertical Height vs longitude but I got
>> warning and I tried to a lot to find my error.
>>
>> here is the wraning
>>
>> warning:ScalarFieldSetValues: 2d coordinate array sfXArray has an
>> incorrect dimension size: defaulting sfXArray
>>
>> here is my data information ncl_filedump and below alos my scrip
>>
>> dimensions:
>>       x = 186
>>       y = 166
>>       pressure = 9
>>       time = 1  // unlimited
>>       nb2 = 2
>>    variables:
>>       float lon ( y, x )
>>          standard_name :        longitude
>>          long_name :    longitude
>>          units :        degrees_east
>>          _CoordinateAxisType :  Lon
>>
>>       float lat ( y, x )
>>          standard_name :        latitude
>>          long_name :    latitude
>>          units :        degrees_north
>>          _CoordinateAxisType :  Lat
>>
>>       float pressure ( pressure )
>>          standard_name :        air_pressure
>>          long_name :    pressure
>>          units :        Pa
>>          positive :     down
>>          axis : Z
>>
>>       double time ( time )
>>          standard_name :        time
>>          long_name :    time
>>          bounds :       time_bnds
>>          units :        seconds since 2009-05-01 00:00:00
>>          calendar :     proleptic_gregorian
>>
>>       double time_bnds ( time, nb2 )
>>          units :        seconds since 2009-05-01 00:00:00
>>          calendar :     proleptic_gregorian
>>
>>  float U ( time, pressure, y, x )
>>          standard_name :        grid_eastward_wind
>>          long_name :    U-component of wind
>>          units :        m s-1
>>          coordinates :  lon lat
>>
>> ;************************************************
>> ;************************************************
>> ;************************************************
>> begin
>> ;************************************************
>> ;open file and read in data
>> ;************************************************
>> ;************************************************
>> ; get variables infromation and print them  cclm
>> ;************************************************
>> vars = getfilevarnames(f)
>> print(vars)
>> ;************************************************
>> var=f->U(0,:,15,:)
>> lon2d=f->lon
>> lev=f->pressure
>>
>> var at lon2d=lon2d
>> var at lev=lev
>> ;*******************************
>> ;create plot
>> ;************************************************
>>
>> ;-- define workstation
>> wks = gsn_open_wks("png","plot_slices")
>> gsn_define_colormap(wks,"ncl_default") ;-- set the colormap to be used
>> ;-- set resources
>> res = True
>> res at tiMainString = "DKRZ NCL Tutorial Example: Slice plot at 40N"
>> res at cnFillOn = True ;-- turn on color fill
>> res at cnLineLabelsOn = False ;-- turns off contour line labels
>> res at cnInfoLabelOn = False ;-- turns off contour info label
>> res at lbOrientation = "vertical" ;-- vertical label bar
>> res at tiYAxisString = var at long_name+" [hPa]"
>> ;-- append units to y-axis label
>> ;res at tfDoNDCOverlay = True
>> res at sfXArray = lon2d ;-- uses lon_t as plot x-axis
>> res at sfYArray = lev/100 ;-- uses lev_t in hPa as plot y-axis
>> res at gsnYAxisIrregular2Linear = True ;-- converts irreg depth to linear
>> res at trYReverse = True ;-- reverses y-axis
>>
>> ;-- generate the plot
>> plot = gsn_csm_contour(wks,var,res)
>> end
>>
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>
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