NCL Sample Scripts Dennis Shea Climate and Global Dynamics Division Climate Analysis Section

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl" f = addfile("erai_ mon.msl_psl.nc","r") ; open file [hdf,grib] p = f->SLP ; (time,lat,lon) ; ( 252,121,240) printVarSummary(p) ; netCDF variable model wks = gsn_open_wks("ps","parvis_1") ; open a PS file plot = gsn_csm_contour_map(wks,p(0,:,:),False) ; default plot ; uses attributes, coordinates B+W graphic NetCDF [NCL] Variable model p = f->SLP NCL reads data values attributes coordinate arrays as a single data object. scalar or array valuesattributescoords p accessed via & _FillValue long_name missing_value units etc. time latitude longitude etc

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl" f = addfile("erai_ mon.msl_psl.nc","r") ; open file [hdf,grib] p = f->SLP ; (time,lat,lon) ; ( 252,121,240) printVarSummary(p) ; netCDF variable model wks = gsn_open_wks("ps","parvis_1") ; open a PS file plot = gsn_csm_contour_map(wks,p(0,:,:),False) ; default plot ; uses attributes, coordinates Variable: p Type: float Total Size: bytes values Number of Dimensions: 3 Dimensions and sizes:[time | 252] x [latitude | 121] x [longitude | 240] Coordinates: time: [ ] latitude: [ ] longitude: [ ] Number Of Attributes: 4 _FillValue :1e+20 units :hPa long_name :Mean sea level pressure missing_value :1e+20 “printVarSummary(p)” output

NetCDF [NCL] Variable model p = f->SLP NCL reads data values attributes coordinate arrays as a single data object. scalar or array valuesattributescoords p accessed via & _FillValue long_name missing_value units etc. time latitude longitude etc Variable: p Type: float Total Size: bytes values Number of Dimensions: 3 Dimensions and sizes:[time | 252] x [latitude | 121] x [longitude | 240] Coordinates: time: [ ] latitude: [ ] longitude: [ ] Number Of Attributes: 4 _FillValue :1e+20 units :hPa long_name :Mean sea level pressure missing_value :1e+20 “printVarSummary(p)” output

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl" f = addfile("erai_ mon.msl_psl.nc","r") ; open file [hdf,grib] p = f->SLP ; (time,lat,lon) ; ( 252,121,240) printVarSummary(p) ; netCDF variable model wks = gsn_open_wks("ps","parvis_1") ; open a PS file plot = gsn_csm_contour_map(wks,p(0,:,:),False) ; default plot

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" f = addfile("erai_ mon.msl_psl.nc","r") ; open file p = f->SLP ; (time,lat,lon) ; ( 252,121,240) pJan = dim_avg_n_Wrap(p(0::12,:,:), 0) ; Jan mean over all years printVarSummary(pJan) wks = gsn_open_wks("ps","parvis_2") ; open PS file gsn_define_colormap(wks,"amwg") ; load predefined color map res = True ; visualization options = True ; color on = True ; span all colors = True ; let NCL pick spacing = "ERAI: : January" plot = gsn_csm_contour_map(wks,pJan,res) Calculating a January monthly mean Variable: pJan Type: float Total Size: bytes values Number of Dimensions: 2 Dimensions and sizes:[latitude | 121] x [longitude | 240] Coordinates: latitude: [ ] longitude: [ ] Number Of Attributes: 5 missing_value :1e+20 long_name :Mean sea level pressure units :hPa _FillValue :1e+20 average_op_ncl :dim_avg_n over dimension(s): time

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" f = addfile("erai_ mon.msl_psl.nc","r") ; open file p = f->SLP(6::12,{0:90},:) ; July ; (20,61,240) w = sqrt(cos( *p&latitude) ) ; weights[*] wp = p*conform(p, w, 1) ; wp[*][*][*] copy_VarCoords(p, wp) x = wp(latitude|:,longitude|:,time|:) ; reorder data neof = 3 eof = eofunc_Wrap(x, neof, False) eof_ts = eofunc_ts_Wrap (x, eof, False) printVarSummary( eof ) ; examine EOF variables printVarSummary( eof_ts ) Calculating EOFS, writing a NetCDF file (next page)

Variable: eof Type: float Total Size: bytes values Number of Dimensions: 3 Dimensions and sizes:[evn | 3] x [latitude | 61] x [longitude | 240] Coordinates: evn: [1..3] latitude: [ 0..90] longitude: [ ] Number Of Attributes: 6 eval_transpose :( , , ) eval :( , , ) pcvar :( , , ) matrix :covariance method :transpose _FillValue :1e+20 Variable: eof_ts Type: float Total Size: 252 bytes 63 values Number of Dimensions: 2 Dimensions and sizes:[evn | 3] x [time | 21] Coordinates: evn: [1..3] time: [ ] Number Of Attributes: 3 ts_mean :( , , ) matrix :covariance _FillValue :1e+20 “ printVarSummary ” output

; Create netCDF: no define mode [simple approach, can be slow] system("/bin/rm -f EOF.nc") ; remove any pre-existing file fout = addfile("EOF.nc", "c") ; new netCDF file = "EOFs of SLP " fout->EOF = eof fout->EOF_TS = eof_ts... the simple way... let NCL do it ; Create netCDF: define mode [classic programmatic approach, faster] dimp = dimsizes(p) ntim = dimp(0) nlat = dimp(1) mlon = dimp(2) system ("/bin/rm -f EOF_define.nc") ; remove any pre-existing file fo = addfile ("EOF_define.nc", "c") ; new netCDF file setfileoption (fo,"DefineMode",True) foAtts = True title = "EOFs of SLP " fileattdef ( fo, foAtts ) ; create file attribute(s) dimNames = (/"time", "latitude", "longitude", "evn"/) ; define dimensions dimSizes = (/ ntim, nlat, mlon, neof/) dimUnlim = (/ False, False, False, False/) filedimdef (fo,dimNames,dimSizes,dimUnlim) evn = eof & evn ; define variables filevardef (fo, "evn", typeof (evn), getvardims (evn)) filevardef (fo, "EOF", typeof (eof), getvardims (eof)) filevardef (fo, "EOF_TS", typeof (eof_ts), getvardims (eof_ts)) ; NCL will create *multiple* attributes filevarattdef (fo,"evn", evn) ; define variable attributes filevarattdef (fo,"EOF", eof) filevarattdef (fo,"EOF_TS", eof_ts) fo->evn = (/ evn /) ; (/.../) means ignore metadata fo->EOF = (/ eof /) fo->EOF_TS = (/ eof_ts /)... the efficient way... predefine file content Two ways to write NetCDF

diri = "/project/convection/ccsm/b40_1850_c02c_76jpf/” fili = systemfunc("cd "+diri+" ; ls b40_cam2.h0.01*nc”) ; 1200 files setfileoption("nc","SuppressClose",False) ) ; user can tell NCL to alter default mode f = addfiles(diri+fili, "r") ; 25 sec (NCO ncrcat 34 sec) t = f[:]->T ; [time|1200]x[lev|30]x[lat|96]x[lon|144] ; 7 sec tt = f[:]->T(:,{500},{-30:30},:) ; [time|1200]x[lat|32]x[lon|144] ; 2 sec Reading multiple (1200) files using “addfiles” netCDF Operators (NCO) can do the same thing ncrcat –v T CAM*nc CAM_T1.nc ncrcat –v T -d lev,18 –d lat 33,54 CAM*nc CAM_T2.nc

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 fili = "PHC2_” + VAR + "_tx0.1v2.JAN.nc" f = addfile(diri + fili,"r") ; for demo, just 1st time and level nSkip = 2 ; make faster... nSkip >1 x = f->SALT(0,0,::nSkip,::nSkip) ; x(nlat,mlon) (2400 x 3600) = f->TLAT(::nSkip,::nSkip) ; 2D curvilinear coordinate arrays = f->TLONG(::nSkip,::nSkip) ;================================================= ; Create contours over a map ;================================================= wks = gsn_open_wks("ps","PHC2_"+VAR+"_"+nSkip) ; open a PS file gsn_define_colormap(wks,"amwg") ; choose colormap i = NhlNewColor(wks,0.8,0.8,0.8) ; add light gray to colormap res = True = True ; turn on color = "RasterFill" ; AreaFill, CellFill = False ; turn off contour lines = True ; use full colormap = -2 ; don't use gray for contours = True ; force cyclic value = "PostDraw" ; do map fill last = “LightGray" ; color of land plot = gsn_csm_contour_map(wks,x,res) end POP scalar example: ‘thinning’ array to speed up plotting

import Ngl, Nio # Open the NetCDF file. nf = Nio.open_file("mtemp.cdf","r") # Get lat/lon/temperature variables. lat = nf.variables["lat"][:] lon = nf.variables["lon"][:] T = nf.variables["t"][0,:,:] # Open a PS workstation. wks = Ngl.open_wks("ps","mecca") # Contour & scalar field resources. res = Ngl.Resources() res.sfXArray = lon res.sfYArray = lat res.cnFillOn = True # Draw contour plot. contour = Ngl.contour(wks,T,res) Ngl.end() PyNGL/PyNIO load "gsn_code.ncl" ; Open the NetCDF file. nf = addfile("mtemp.cdf","r") ; Get lat/lon/temperature variables. lat = nf->lat lon = nf->lon T = nf->t(0,:,:) ; Open a PS workstation. wks = gsn_open_wks("ps","mecca") ; Contour & scalar field resources. res = True = lon = lat = True = False ; Draw contour plot. contour = gsn_contour(wks,T,res) NCL Sample PyNGL/PyNIO and NCL/GSUN scripts