Re: overlaying gradient contours

I see the issue

  plot=gsn_csm_contour_map_overlay(wks,u,vdiv*1e5,res1,res2)

The "vdiv*1e5" creates a temporary variable that contains
no meta data.

replace the above with the following

  vdiv = vdiv*1e5

  plot=gsn_csm_contour_map_overlay(wks,u,vdiv,res1,res2)

Adam Phillips wrote:
> Hi Chris,
> From what you sent in the original email:
>
> >>> Variable: u
> >>> Type: float
> >>> Total Size: 42048 bytes
> >>> 10512 values
> >>> Number of Dimensions: 2
> >>> Dimensions and sizes: [lat | 73] x [lon | 144]
> >>> Coordinates:
> >>> lat: [90..-90] <================= latitude coordinate
> variable
> >>> lon: [ 0..357.5] <=============== longitude coordinate
> variable
> >>> Number Of Attributes: 15
>
> The latitude and longitude coordinate information is attached to the u /
> v arrays. So you should be good to go there. However, NCL also needs the
> units attribute of the latitude/longitude coordinate variables to be set
> as well. The units attribute is usually set in the netCDF file, but not
> always. The "Data either does not contain a valid latitude coordinate
> array or doesn't contain one at all." error message is an indication
> that this might be the problem.
>
> Try this:
>
> dir = "/home/cgf/projects/"
> f = addfile (dir+"uwnd200.nc", "r")
> u = f->uwnd ; (lat,lon)
> f2 = addfile (dir+"vwnd200.nc", "r")
> v = f2->vwnd
>
> u&lat_at_units = "degrees_north"
> u&lon_at_units = "degrees_east"
> v&lat_at_units = "degrees_north"
> v&lon_at_units = "degrees_east"
> udiv=u
> vdiv=v
> gradsf(u,udiv,vdiv)
>
> ; plot as normal
>
> There is a FAQ written for that specific error message, if you'd like to
> learn more:
> http://www.ncl.ucar.edu/FAQ/#err_msgs_012
>
> Let us know if that doesn't fix your issue.
> Best regards,
> Adam
>
> Chris Fletcher wrote:
>> Thanks for your reply. I removed the lines as suggested but I still get
>> the same problem, and warning about "Data either does not contain a
>> valid latitude coordinate array or doesn't contain one at all."
>>
>> I'm still unclear about the lat/lon2d arrays for this grid. Are they
>> required? If so, should I create them on the fly (I don't think they
>> are available to be read from the data file), then assign them using
>> u_at_lon2d and u_at_lat2d?
>>
>> On Fri, 2009-08-14 at 08:07 -0600, Dennis Shea wrote:
>>> [1]
>>> These are *not* two-dimensional latitude or longitude arrays.
>>> The variables u and vdiv are two-dimensiona BUT the
>>> coordinate variables are classic netCDF one dimensional
>>> coordinates.
>>>
>>> By Unidata/netCDF definition a "coordinate variable"
>>> is a one-dimensional array of monotonically {in/de}creasing
>>> values"
>>>
>>> Variable: u
>>> Type: float
>>> Total Size: 42048 bytes
>>> 10512 values
>>> Number of Dimensions: 2
>>> Dimensions and sizes: [lat | 73] x [lon | 144]
>>> Coordinates:
>>> lat: [90..-90] <=== coord variable
>>> lon: [ 0..357.5] <=== coord variable
>>>
>>>
>>> Remove:
>>> lat2d = f->lat
>>> lon2d = f->lon
>>> printVarSummary(lat2d)
>>> printVarSummary(lon2d)
>>>
>>> u_at_lon2d=lon2d
>>> u_at_lat2d=lat2d
>>> v_at_lon2d=lon2d
>>> v_at_lat2d=lat2d
>>>
>>> [2] Delete or comment the following
>>>
>>> res1_at_mpMinLonF = 0. ; select a subregion
>>> res1_at_mpMaxLonF = 360.
>>> res1_at_mpMinLatF = -90.
>>> res1_at_mpMaxLatF = 90.
>>>
>>> The default is a global grid.
>>>
>>> ======================================
>>> Good luck
>>>
>>>
>>> Chris Fletcher wrote:
>>>> Hi, question from a new user:
>>>>
>>>> I am trying to use gsn_csm_contour_map_overlay to display an NCEP/NCAR
>>>> reanalysis wind field (shaded) and its meridional gradient (contour).
>>>>
>>>> However, the contour data won't plot correctly (it appears compressed
>>>> into a smaller region in the top-right -- see attached). I believe the
>>>> lon/lat2d variables and their "units" attribute are defined correctly
>>>> (although the warnings suggest otherwise). The problem appears to be
>>>> that the gradsf procedure modifies the coordinates somehow, because I
>>>> can contour overlay the wind field with itself without a problem.
>>>>
>>>> Thanks in advance, all the output follows.
>>>> Chris
>>>>
>>>>
>>>>
>>>> I see the following warnings from my script:
>>>> (0) is_valid_latlon2d_attr: Warning: The 'lat2d' attribute must
>>>> either be the same dimension sizes as the data, or one element larger in
>>>> both directions. Your data will most likely not be overlaid on the map
>>>> correctly.
>>>> (0) is_valid_latlon2d_attr: Warning: The 'lon2d' attribute must
>>>> either be the same dimension sizes as the data, or one element larger in
>>>> both directions. Your data will most likely not be overlaid on the map
>>>> correctly.
>>>> (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'
>>>>
>>>>
>>>>
>>>> ;Here are the details from printVarSummary
>>>> ;***********************************************
>>>> Variable: lat2d
>>>> Type: float
>>>> Total Size: 292 bytes
>>>> 73 values
>>>> Number of Dimensions: 1
>>>> Dimensions and sizes: [lat | 73]
>>>> Coordinates:
>>>> lat: [90..-90]
>>>> Number Of Attributes: 3
>>>> units : degrees_north
>>>> actual_range : ( 90, -90 )
>>>> long_name : Latitude
>>>>
>>>>
>>>> Variable: lon2d
>>>> Type: float
>>>> Total Size: 576 bytes
>>>> 144 values
>>>> Number of Dimensions: 1
>>>> Dimensions and sizes: [lon | 144]
>>>> Coordinates:
>>>> lon: [ 0..357.5]
>>>> Number Of Attributes: 3
>>>> units : degrees_east
>>>> long_name : Longitude
>>>> actual_range : ( 0, 357.5 )
>>>>
>>>>
>>>> Variable: u
>>>> Type: float
>>>> Total Size: 42048 bytes
>>>> 10512 values
>>>> Number of Dimensions: 2
>>>> Dimensions and sizes: [lat | 73] x [lon | 144]
>>>> Coordinates:
>>>> lat: [90..-90]
>>>> lon: [ 0..357.5]
>>>> Number Of Attributes: 15
>>>> lat2d : <ARRAY of 73 elements>
>>>> lon2d : <ARRAY of 144 elements>
>>>> long_name : Monthly mean u wind
>>>> actual_range : ( -66.37, 124.4 )
>>>> valid_range : ( -125, 160 )
>>>> units : m/s
>>>> missing_value : 32766
>>>> precision : 2
>>>> least_significant_digit : 1
>>>> var_desc : u-wind
>>>> U
>>>> dataset : CDC Derived NCEP Reanalysis Products
>>>> AC
>>>> level_desc : Multiple levels
>>>> F
>>>> statistic : Mean
>>>> M
>>>> parent_stat : Other
>>>> -
>>>> _FillValue : 32766
>>>>
>>>>
>>>> Variable: vdiv
>>>> Type: float
>>>> Total Size: 42048 bytes
>>>> 10512 values
>>>> Number of Dimensions: 2
>>>> Dimensions and sizes: [lat | 73] x [lon | 144]
>>>> Coordinates:
>>>> lat: [90..-90]
>>>> lon: [ 0..357.5]
>>>> Number Of Attributes: 15
>>>> _FillValue : 32766
>>>> parent_stat : Other
>>>> -
>>>> statistic : Mean
>>>> M
>>>> level_desc : Multiple levels
>>>> F
>>>> dataset : CDC Derived NCEP Reanalysis Products
>>>> AC
>>>> var_desc : v-wind
>>>> V
>>>> least_significant_digit : 1
>>>> precision : 2
>>>> missing_value : 32766
>>>> units : m/s
>>>> valid_range : ( -125, 160 )
>>>> actual_range : ( -66.65, 66.39 )
>>>> long_name : Monthly mean v wind
>>>> lon2d : <ARRAY of 144 elements>
>>>> lat2d : <ARRAY of 73 elements>
>>>>
>>>>
>>>>
>>>> Here is my script:
>>>> ;***********************************************
>>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>>>> ;*************************************************
>>>> begin
>>>> ;*************************************************
>>>> dir = "/home/cgf/projects/"
>>>> f = addfile (dir+"uwnd200.nc", "r")
>>>> u = f->uwnd ; (lat,lon)
>>>> lat2d = f->lat
>>>> lon2d = f->lon
>>>> f2 = addfile (dir+"vwnd200.nc", "r")
>>>> v = f2->vwnd
>>>> printVarSummary(lat2d)
>>>> printVarSummary(lon2d)
>>>>
>>>> u_at_lon2d=lon2d
>>>> u_at_lat2d=lat2d
>>>> v_at_lon2d=lon2d
>>>> v_at_lat2d=lat2d
>>>> udiv=u
>>>> vdiv=v
>>>> gradsf(u,udiv,vdiv)
>>>> ;
>>>> ; ************
>>>> ; plotting
>>>> ;
>>>> ;
>>>> wks = gsn_open_wks("ps","wind") ; open a workstation
>>>> gsn_define_colormap(wks,"BlWhRe")
>>>> ;************************************************
>>>> ; resource list for first data array
>>>> ;************************************************
>>>> res1 = True
>>>> res1_at_gsnDraw = False ; don"t draw
>>>> res1_at_gsnFrame = False ; don"t advance frame
>>>>
>>>> res1_at_cnLevelSelectionMode = "ManualLevels" ; set manual contour levels
>>>> res1_at_cnMinLevelValF = -5. ; set min contour level
>>>> res1_at_cnMaxLevelValF = 45. ; set max contour level
>>>> res1_at_cnLevelSpacingF = 2 ; set contour spacing
>>>>
>>>> res1_at_lbOrientation = "Vertical" ; vertical label bar
>>>> res1_at_lbLabelAutoStride = True ; optimal label stride
>>>> res1_at_gsnSpreadColors = True ; use full range of colors
>>>> res1_at_gsnSpreadColorEnd = -3 ; don"t use added gray
>>>>
>>>> ; res1_at_mpCenterLonF = 180. ; center plot at 180
>>>>
>>>> res1_at_mpMinLonF = 0. ; select a subregion
>>>> res1_at_mpMaxLonF = 360.
>>>> res1_at_mpMinLatF = -90.
>>>> res1_at_mpMaxLatF = 90.
>>>>
>>>> ;************************************************
>>>> ; resource list for second data array
>>>> ;************************************************
>>>> res2 = True
>>>> res2_at_cnLevelSelectionMode = "ManualLevels" ; set manual contour levels
>>>> res2_at_cnMinLevelValF = -10. ; set min contour level
>>>> res2_at_cnMaxLevelValF = 10. ; set max contour level
>>>> res2_at_cnLevelSpacingF = 0.5 ; set contour spacing
>>>> res2_at_cnLineLabelsOn = True
>>>> res2_at_gsnContourZeroLineThicknessF = 2. ; doubles thickness of
>>>> zero contour
>>>> res2_at_gsnContourNegLineDashPattern = 1 ; sets negative contours
>>>> to dash pattern 1
>>>>
>>>> printVarSummary(u)
>>>> printVarSummary(vdiv)
>>>>
>>>> plot=gsn_csm_contour_map_overlay(wks,u,vdiv*1e5,res1,res2)
>>>> draw(plot)
>>>> frame(wks)
>>>> end
>>>>
>>>>
>>>>
>>
>> _______________________________________________
>> ncl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Fri Aug 14 2009 - 10:19:07 MDT