Re: plotting a regional zoom of a lambert conformal grid

Hello all,

Steve's issue was resolved by attaching the 2D latitudes/longitudes to
his data array, and by setting tfDoNDCOverlay = False (which is the
default). Specifically, if the variable to be plotted is "x"

       x = f->FOO
       x_at_lon2d = f->XLON ; XLON is the 2d array on the file
       x_at_lat2d = f->XLAT

The special attributes "lat2d" and "lon2d" are recognized
by the gsn plotting routines.

=======

This example brings up a very good point. When you are dealing with two
dimensional latitudes/longitudes, you have 2 choices when it comes to
plotting the data:

1) set tfDoNDCOverlay = True, mpLimitMode = "Corners", and the
mpLeftCornerLatF, mpLeftCornerLonF, mpRightCornerLatF, and
mpRightCornerLonF resources. In terms of drawing speed this is the
fastest way. The limitation is that you cannot zoom in onto a
particular region. This method is faster because NCL takes the
data passed into the plotting function and draws it in the
region specified by the mp*Corner*F resources above. No
map transformation computations are performed.

or

2) attach the 2D lats,lons to the array. (See above and
http://www.ncl.ucar.edu/Applications/Scripts/popscal_1.ncl).
This method draws slightly slower than the first method
because it computes the required map transformations.
The advantage is that it allows the flexibility of
zooming in onto a particular region.

Adam + Dennis

Steve Nesbitt wrote:
> Hello,
>
> I am trying to plot RUC model data using NCL (4.2.0.a033 on linux). I
> can plot maps of the data over the entire domain, but when I try to
> subset the data over the Midwest, for example (if you look carefully)
> the map zooms in but the data does not. The attached images show this
> behavior. See the script below for my attempt at zooming in. If you
> want access to the raw data to try, let me know.
>
> Thanks,
> -Steve
>
>
> ;*******************************************************
> ; plotetaruc.ncl
> ;*******************************************************
> 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
> ;************************************************
> ; open file and read in data
> ;************************************************
> diri = "./"
> fili = "my.grb"
> f = addfile (diri+fili, "r")
> names = getfilevarnames(f)
> ; print(names)
> ; printVarSummary(names)
>
> atts = getfilevaratts(f,names(0))
> ; dims = getfilevardims(f,names(0))
> ; print(atts)
> ; print(dims)
>
> ; get vars
>
>
> w = f->V_VEL_252_ISBL
> u = f->U_GRD_252_ISBL
> v = f->V_GRD_252_ISBL
> z = f->HGT_252_ISBL
> zeta = f->ABS_V_252_ISBL
> t = f->TMP_252_ISBL
> t_sfc = f->TMP_252_SFC
> u_sfc = f->U_GRD_252_HTGL
> v_sfc = f->V_GRD_252_HTGL
> pmsl = f->MSLMA_252_MSL
> rh = f->R_H_252_ISBL
> spd = u*0.
> spd = (u^2.+v^2)^0.5
> prate= f->PRATE_252_SFC
>
> pres = f->lv_ISBL2
> lat2d = f->gridlat_252
> lon2d = f->gridlon_252
>
> time=w_at_initial_time
> print(time)
> ;printVarSummary(lat)
>
> dims=dimsizes(w)
> ; print(dims)
> nlon=dims(2)
> nlat=dims(1)
>
> ; print(nlon)
> ; print(nlat)
> ; print(var)
> ; print(pres(12))
> ; printVarSummary(var)
> ; printVarSummary(lon2d)
> ; printVarSummary(lat2d)
>
> ;*************************
> ;common plotting resources
> ;*************************
>
> res = True ; plot mods desired
> res_at_gsnDraw = False
> res_at_gsnFrame = False
> res_at_cnLinesOn = False
> res_at_cnFillOn = True ; color plot desired
> res_at_cnLineLabelsOn = False ; turn off contour lines
> res_at_gsnAddCyclic = False
> ; !!!!! any plot of data that is on a native grid, must use the "corners"
> ; method of zooming in on map.
>
> ;**** ZOOMED IN
> res_at_mpLimitMode = "Corners" ; choose range of map
> res_at_mpLeftCornerLatF = 35.
> res_at_mpLeftCornerLonF = -105.
> res_at_mpRightCornerLatF = 47.
> res_at_mpRightCornerLonF = -80.
> ;**** ZOOMED OUT
> res_at_mpLimitMode = "Corners" ; choose range of map
> res_at_mpLeftCornerLatF = lat2d(0,0)
> res_at_mpLeftCornerLonF = lon2d(0,0)
> res_at_mpRightCornerLatF = lat2d(nlat-1,nlon-1)
> res_at_mpRightCornerLonF = lon2d(nlat-1,nlon-1)
>
> ;
> ; The following 4 pieces of information are REQUIRED to properly display
> ; data on a native lambert conformal grid. This data should be specified
> ; somewhere in the model itself.
>
> ; WARNING: our local RCM users could not provide us with this information,
> ; so this is our best guess as to the correct numbers. Use at your own risk.
>
> res_at_mpProjection = "LambertConformal"
> res_at_mpLambertParallel1F = lon2d_at_Latin1
> res_at_mpLambertParallel2F = lon2d_at_Latin2
> res_at_mpLambertMeridianF = lon2d_at_Lov
>
> ; usually, when data is placed onto a map, it is TRANSFORMED to the
> specified
> ; projection. Since this model is already on a native lambert conformal
> grid,
> ; we want to turn OFF the tranformation.
>
> res_at_tfDoNDCOverlay = True
>
> res_at_mpGeophysicalLineColor = "red" ; color of
> continental outlines
> res_at_mpPerimOn = True ; draw box
> around map
> res_at_mpGridLineDashPattern = 2 ; lat/lon lines
> as dashed
> res_at_mpOutlineBoundarySets = "GeophysicalAndUSStates" ; add state
> boundaries
> res_at_mpUSStateLineColor = "red" ; make them red
> res_at_pmTickMarkDisplayMode = "Always" ; turn on tickmarks
> res_at_cnLineLabelInterval = 1
> res_at_cnLabelMasking = True
> res_at_gsnSpreadColors=True
> res_at_gsnSpreadColorStart = 3
> res_at_gsnSpreadColorEnd = 19
> wks = gsn_open_wks("ps","ruc_300") ; open a workstation
> ;plot=new(4,graphic)
> gsn_define_colormap(wks,"gui_default") ; choose colormap
>
> ;************************************************
> ; create plot: upper left
> ;************************************************
>
> res1=res
> res1_at_tiMainString=time
> res1_at_gsnLeftString="300hPa height(dm), wind speed(m/s) "
> res1_at_cnLevelSelectionMode = "ManualLevels" ; manual levels
> res1_at_cnMinLevelValF = 10. ; min level
> res1_at_cnMaxLevelValF = 100. ; max level
> res1_at_cnLevelSpacingF = 10 ; contour spacing
>
>
> res2=True
>
>
> res2_at_tfDoNDCOverlay = True
> res2_at_cnInfoLabelOn = False
> res2_at_cnMinLevelValF = 900.+12*12 ; set min contour
> level
> res2_at_cnMaxLevelValF = 900.-12*12 ; set max contour
> level
> res2_at_cnLevelSpacingF = 12. ; set contour spacing
> res2_at_cnLineLabelsOn = True
> res2_at_cnLineLabelInterval = 1
> res2_at_cnLabelMasking = True
> ; res2_at_cnHighLabelsOn = True; label highs
> ; res2_at_cnHighLabelString = "H"; highs' label
> ; res2_at_cnHighLabelFontHeightF = 0.03; larger H labels
> ; res2_at_cnHighLabelFont = "helvetica-bold"; H labels font
> ; res2_at_cnHighLabelBackgroundColor = "Transparent"; no box
> ; res2_at_cnLowLabelsOn = True; label lows
> ; res2_at_cnLowLabelString = "L"; lows' label
> ; res2_at_cnLowLabelFontHeightF = 0.03; larger L labels
> ; res2_at_cnLowLabelFont = "helvetica-bold"; L labels font
> ; res2_at_cnLowLabelBackgroundColor = "Transparent"; no box
> ; res2_at_cnConpackParams = (/ "HLX:6, HLY:6" /)
>
> index300=ind(pres.eq.300.)
>
> plot1 =
> gsn_csm_contour_map_overlay(wks,spd(index300,:,:),z(index300,:,:)/10.,res1,res2)
> ; Draw contours over a map.
>
> draw(plot1)
> frame(wks)
>
>
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk_at_ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk

-- 
--------------------------------------------------------------
Adam Phillips			             asphilli_at_ucar.edu
National Center for Atmospheric Research   tel: (303) 497-1726
ESSL/CGD/CAS                               fax: (303) 497-1333
P.O. Box 3000				
Boulder, CO 80307-3000	  http://www.cgd.ucar.edu/cas/asphilli
_______________________________________________
ncl-talk mailing list
ncl-talk_at_ucar.edu
http://mailman.ucar.edu/mailman/listinfo/ncl-talk