;************************************************* ; rdm2grid_1.ncl ;************************************************* ; ; Concepts illustrated: ; - Reading SLP from netCDF ; - Using array syntax[ ::-1 ] so that lat is South-to-North ; - Generating random index values for demo ; - Using natgrid to interpolate to grid ; - Plotting original and reconstructed grids ; ; 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 NOBS = 500 ;------------------------------------------------------------------ ; Read data ;------------------------------------------------------------------ diri = "./" fili = "slp_1988mm.nc" f = addfile(diri+fili, "r") Z = f->slp(0,::-1,:) ; natgrid requires monotonic increasing y [lat] ;------------------------------------------------------------------ ; Generate N random values from the above ;------------------------------------------------------------------ dimz = dimsizes( Z ) nlat = dimz(0) mlon = dimz(1) N = nlat*mlon iZ = generate_unique_indices( N ) ;iZ = floattoint(random_uniform (0, N-1, N)) trip = grid2triple (Z&lon, Z&lat, Z) dlon = Z&lon(2)-Z&lon(1) reps = random_uniform (-dlon, dlon, N) ; minor location perturbations IOBS = iZ(0:NOBS) ; convenience ; clarity only ... create explicit variables rlon = trip(0,IOBS) + reps(IOBS) rlat = trip(1,IOBS) + reps(IOBS(::-1)) rZ = trip(2,IOBS) rlon@units = "degrees_east" rlat@units = "degrees_north" ;------------------------------------------------------------------ ; natgrid ;------------------------------------------------------------------ zgrd = natgrid_Wrap (rlon, rlat, rZ, Z&lon, Z&lat) znat = transpose(zgrd) ;------------------------------------------------------------------ ; plot ;------------------------------------------------------------------ maxLev = 16 mnmxint = nice_mnmxintvl( min(znat), max(znat), maxLev, True) dimznat = dimsizes(znat) kplt = dimznat(0) wks = gsn_open_wks("png","rdm2grid") ; send graphics to PNG file plot = new(2,graphic) res = True res@gsnDraw = False ; don't draw res@gsnFrame = False ; don't advance frame res@cnFillOn = True ; turn on color res@cnFillPalette = "amwg" ; set color map ;res@cnLinesOn = False ; turn off contour lines res@cnLineLabelsOn = False ; turn off contour line labels res@lbLabelBarOn = False ; turn off individual cb's res@mpCenterLonF = 180. res@cnLevelSelectionMode = "ManualLevels" res@cnMinLevelValF = mnmxint(0) res@cnMaxLevelValF = mnmxint(1) res@cnLevelSpacingF = mnmxint(2) pmres = True pmres@gsMarkerIndex = 16 ; Filled circle pmres@gsMarkerSizeF = 0.0125 res@gsnCenterString = "Original grid" plot(0) = gsn_csm_contour_map(wks,Z,res) res@gsnCenterString = "NATGRID: N="+NOBS plot(1) = gsn_csm_contour_map(wks,znat,res) ; add polymarkers dum1 = gsn_add_polymarker(wks, plot(1), rlon, rlat, pmres) ;************************************************ ; create panel ;************************************************ resP = True ; modify the panel plot resP@gsnPanelMainString = "Insert your own title here" resP@gsnMaximize = True ; make large resP@gsnPanelLabelBar = True ; add common colorbar ;resP@lbLabelStride = 2 ; force every other label ;resP@lbLabelFontHeightF = 0.0125 ; make labels smaller [0.2 default] gsn_panel(wks,plot,(/2,1/),resP) ; now draw as one plot end