[ncl-talk] where am I getting wrong in plotting the values please help....
gurbrinder aulakh
gurbrinderaulakh at yahoo.co.in
Thu Jun 1 01:38:09 MDT 2017
Dear Mary Haley,Thanks a lot for your reply... I really appreciate that. Your explanation was crystal clear. I have used ncl_filedump and made changes accordingly by replacing YCells and XCells with latitude and longitude....Then I have warnings like
(0) gsn_add_cyclic: Warning: The range of your longitude data is not 360.(0) You may want to set gsnAddCyclic to False to avoid a warning(0) message from the spline function.(0) gsn_add_cyclic: Warning: The range of your longitude data is not 360.(0) You may want to set gsnAddCyclic to False to avoid a warning(0) message from the spline function.warning:VectorFieldSetValues: irregular coordinate array vfXArray non-monotonic: defaulting vfXArray
I have added res at gsnAddCyclic = False res at gsnAddCyclic = False but still left with the last warning.....warning:VectorFieldSetValues: irregular coordinate array vfXArray non-monotonic: defaulting vfXArray
Here is my code with changes begin
uf = addfile("uwind500.nc","r") vf = addfile("vwind500.nc","r") u = uf->UGRD_500_ISBL(0,:,:) v = vf->VGRD_500_ISBL(0,:,:)
lat=uf->latitude(:,0)lon=uf->longitude(0,:)
u&YCells = uf->latitude(: ,0)u&XCells = uf->longitude(0,:)
v&YCells = vf->latitude(:,0)v&XCells= vf->longitude(0,:)
printVarSummary(u)
div = uv2dvG_Wrap(u,v) ; u,v ==> divergence
dv2uvg(div,u,v) ; div ==> divergent wind components
u at long_name = "Zonal Divergent Wind" u at units = u at units v at long_name = "Meridional Divergent Wind" v at units = v at units
;*************************************************; plot results;************************************************* wks = gsn_open_wks("png","wind123") ; send graphics to PNG file res = True res at vcRefMagnitudeF = 3. ; make vectors larger res at vcRefLengthF = 0.050 ; reference vector length res at vcGlyphStyle = "CurlyVector" ; turn on curly vectors res at vcMinDistanceF = 0.012 ; thin the vectors res at gsnAddCyclic = False res at gsnLeftString = "Divergent Wind" ; plot 1st time step plot= gsn_csm_vector_map(wks,u(:,:),v(:,:),res)
end
output of the uwind500.nc is also attached... please help me to understand am i reading the data right...thanks a lot for time and help....
Regards,Gurbrinder Kaur
On Tuesday, 30 May 2017 10:04 PM, Mary Haley <haley at ucar.edu> wrote:
I think you need to look at your data more closely.
My guess is that YCells and XCells are not actually lat / lon arrays, but yet you are trying to use them to plot your data over a map.
You have this code, which looks like you were trying to get NCL to recognize YCells and XCells as lat/lon arrays:
lat = uf->u&YCells
lon = uf->v&XCells
u!0="lat"
u!1="lon"
u&lat at units="degrees_north"
u&lon at units="degrees_east"
However, I'm suspicious that YCells and XCells actually represent the latitude and longitude values of your array.
It helps if you use "printVarSummary" to look at your data before you plot it:
printVarSummary(u)
The above should also print the numeric range of the lat / lon arrays, and you will see very quickly whether they actually look like lat / lon values.
Variable : u Type : float . . . Number of Dimensions: 2 Dimensions and sizes: [lat | some number] x [lon | some number] Coordinates: lat: [...you'll see a numeric range here...] lon: [...ditto...] Number Of Attributes:
If u has an attribute called "coordinates", then it is very important to pay attention to this because this will likely tell you what the name is of your lat/lon arrays on the file, which you will need to use to replace "YCells" and "XCells". It would look something like this:
Variable : u Type : float . . . Number of Dimensions: 2 Dimensions and sizes: [lat | some number] x [lon | some number] Coordinates: lat: [...you'll see a numeric range here...] lon: [...ditto...] Number Of Attributes: 5 coordinates: "latitude longitude"
Important note: the "coordinates" attribute is a different thing than "Coordinates", which you *always* see when you do a printVarSummary. The "Coordinates" output from printVarSummary represents coordinate *arrays* that may already be attached to your file.
If you do see a "coordinates" attribute, then make note of the names in the attribute, then do an "ncl_filedump" on your file on the UNIX command line to see if your file contains variables with these names. If it does, then you can replace this code:
lat = uf->u&YCells
lon = uf->v&XCells
u!0="lat"
u!1="lon"
u&lat at units="degrees_north"
u&lon at units="degrees_east"
with:
u!0="lat"
u!1="lon"
u&lat := uf->latitude ; The ":=" forces YCell and XCell to be overwritten, in caseu&lon := uf->longitude ; they are different types than latitude and longitude.
You need to do the same for "v":
v!0="lat"
v!1="lon"
v&lat = vf->latitudev&lon = vf->longitude
If the above doesn't work, then it would help if you could email ncl-talk and provide the output from doing an "ncl_filedump" on uwind500.nc.
--Mary
On Tue, May 30, 2017 at 3:36 AM, gurbrinder aulakh <gurbrinderaulakh at yahoo.co.in> wrote:
I want to compute wind divergence reading u and v wind components but I am getting the following warnings when I run the script.Plot is also not as expected... Please help tried everything from the earlier queries but not finding any solution.... Am I reading the correct values....Thanks in advance..
warning:IrTransInitialize: trYCoordPoints contains invalid coordinate array: defaulting trYAxisType to LinearAxiswarning: AutoComputeMajorTickMarks: min and max are so close together or so far apart that arithmetic error may cause problems, proceed at own riskwarning:ComputeMinorTickMarks: The distance between major tickmarks is so close or so far apart that arithmetic error may cause problems determining the accurate locations of minor tickmarkswarning: AutoComputeMajorTickMarks: min and max are so close together or so far apart that arithmetic error may cause problems, proceed at own riskwarning:ComputeMinorTickMarks: The distance between major tickmarks is so close or so far apart that arithmetic error may cause problems determining the accurate locations of minor tickmarkswarning: StreamlinePlotInitialize: coordinate spacing is irregular; linear spacing only possible using index coordinates for Y Axiswarning:IrTransInitialize: trYCoordPoints contains invalid coordinate array: defaulting trYAxisType to LinearAxis
****************************** *******************;; These files are loaded by default in NCL V6.2.0 and newer; 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
uf = addfile("uwind500.nc","r") vf = addfile("vwind500.nc","r") u = uf->UGRD_500_ISBL(0,:,:) v = vf->VGRD_500_ISBL(0,:,:)
lat = uf->u&YCells lon = uf->v&XCells
u!0="lat"u!1="lon"
u&lat at units="degrees_north"u&lon at units="degrees_east"
printVarSummary(u); div = uv2dvG_Wrap(u,v) ; u,v ==> divergence
dv2uvg(div,u,v) ; div ==> divergent wind components
u at long_name = "Zonal Divergent Wind" u at units = u at units v at long_name = "Meridional Divergent Wind" v at units = v at units
;***************************** ********************; plot results;***************************** ******************** wks = gsn_open_wks("png","wind123") ; send graphics to PNG file res = True res at vcRefMagnitudeF = 3. ; make vectors larger res at vcRefLengthF = 0.050 ; reference vector length res at vcGlyphStyle = "CurlyVector" ; turn on curly vectors res at vcMinDistanceF = 0.012 ; thin the vectors
res at gsnLeftString = "Divergent Wind" ; plot 1st time step plot= gsn_csm_vector_map(wks,u(:,:), v(:,:),res)
end
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