; ============================================================== ; eof_1.ncl ; ; Concepts illustrated: ; - Calculating EOFs ; - Drawing a time series plot ; - Using coordinate subscripting to read a specified geographical region ; - Rearranging longitude data to span -180 to 180 ; - Calculating symmetric contour intervals ; - Drawing filled bars above and below a given reference line ; - Drawing subtitles at the top of a plot ; - Reordering an array ; ============================================================== ; NCL V6.4.0 has new functions eofunc_n_Wrap and ; eofunc_ts_n_Wrap that allow you to calculate the EOFs without ; first having to first reorder the data. See eof_1_640.ncl. ; ============================================================== ; Calculate EOFs of the Sea Level Pressure over the North Atlantic. ; ============================================================== ; The slp.mon.mean file can be downloaded from: ; http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.surface.html ; ============================================================== ; 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 ; ============================================================== ; User defined parameters that specify region of globe and ; ============================================================== latS = 25. latN = 80. lonL = -70. lonR = 40. yrStrt = 2015 yrLast = 2018 season = "DJF" ; choose Dec-Jan-Feb seasonal mean neof = 2 ; number of EOFs optEOF = True optEOF@jopt = 0 ; This is the default; most commonly used; no need to specify. ;;optEOF@jopt = 1 ; **only** if the correlation EOF is desired optETS = False ; ============================================================== ; Open the file: Read only the user specified period ; ============================================================== f=addfile("/home/peni/skripsi/olr.day.anomalies.2015-2018.nc","r") TIME = f->time YYYY = cd_calendar(TIME,-1)/100 ; entire file iYYYY = ind(YYYY.ge.yrStrt .and. YYYY.le.yrLast) OLR_anom = f->OLR_anom(iYYYY,:,:) printVarSummary(OLR_anom) ; variable overview ; ============================================================== ; dataset longitudes span 0=>357.5 ; Because EOFs of the North Atlantic Oscillation are desired ; use the "lonFlip" (contributed.ncl) to reorder ; longitudes to span -180 to 177.5: facilitate coordinate subscripting ; ============================================================== OLR_anom = lonFlip(OLR_anom) printVarSummary(OLR_anom) ; note the longitude coord ; ============================================================== ; compute desired global seasonal mean: month_to_season (contributed.ncl) ; ============================================================== OLR_ANOM = month_to_season (OLR_anom, season) nyrs = dimsizes(OLR_ANOM&time) printVarSummary(OLR_ANOM) ; ================================================================= ; create weights: sqrt(cos(lat)) [or sqrt(gw) ] ; ================================================================= rad = 4.*atan(1.)/180. clat = f->lat clat = sqrt( cos(rad*clat) ) ; gw for gaussian grid ; ================================================================= ; weight all observations ; ================================================================= wOLR_ANOM = OLR_ANOM ; copy meta data wOLR_ANOM = OLR_ANOM*conform(OLR_ANOM, clat, 1) wOLR_ANOM@long_name = "Wgt: "+wOLR_ANOM@long_name ; ================================================================= ; Reorder (lat,lon,time) the *weighted* input data ; Access the area of interest via coordinate subscripting ; ================================================================= xw = wOLR_ANOM({lat|latS:latN},{lon|lonL:lonR},time|:) x = wOLR_ANOM(time|:,{lat|latS:latN},{lon|lonL:lonR}) eof = eofunc_Wrap(xw, neof, optEOF) eof_ts = eofunc_ts_Wrap (xw, eof, optETS) printVarSummary( eof ) ; examine EOF variables printVarSummary( eof_ts ) ; ================================================================= ; Normalize time series: Sum spatial weights over the area of used ; ================================================================= dimxw = dimsizes( xw ) mln = dimxw(1) sumWgt = mln*sum( clat({lat|latS:latN}) ) eof_ts = eof_ts/sumWgt ; ================================================================= ; Extract the YYYYMM from the time coordinate ; associated with eof_ts [same as SLP&time] ; ================================================================= yyyymm = cd_calendar(eof_ts&time,-2)/100 ;;yrfrac = yyyymm_to_yyyyfrac(yyyymm, 0.0); not used here ;============================================================ ; PLOTS ;============================================================ wks = gsn_open_wks("png","eof") ; send graphics to PNG file plot = new(neof,graphic) ; create graphic array ; only needed if paneling ; EOF patterns res = True res@gsnDraw = False ; don't draw yet res@gsnFrame = False ; don't advance frame yet res@gsnAddCyclic = False ; plotted dataa are not cyclic res@mpFillOn = False ; turn off map fill res@mpMinLatF = latS ; zoom in on map res@mpMaxLatF = latN res@mpMinLonF = lonL res@mpMaxLonF = lonR res@cnFillOn = True ; turn on color fill res@cnLinesOn = False ; True is default ;res@cnLineLabelsOn = False ; True is default res@cnFillPalette = "BlWhRe" ; set color map res@lbLabelBarOn = False ; turn off individual lb's ; set symmetric plot min/max symMinMaxPlt(eof, 16, False, res) ; contributed.ncl ; panel plot only resources resP = True ; modify the panel plot resP@gsnMaximize = True ; large format resP@gsnPanelLabelBar = True ; add common colorbar yStrt = yyyymm(0)/100 yLast = yyyymm(nyrs-1)/100 resP@gsnPanelMainString = "SLP: "+season+": "+yStrt+"-"+yLast ;******************************************* ; first plot ;******************************************* do n=0,neof-1 res@gsnLeftString = "EOF "+(n+1) res@gsnRightString = sprintf("%5.1f", eof@pcvar(n)) +"%" plot(n)=gsn_csm_contour_map(wks,eof(n,:,:),res) end do gsn_panel(wks,plot,(/neof,1/),resP) ; now draw as one plot ;******************************************* ; second plot ;******************************************* ; EOF time series [bar form] rts = True rts@gsnDraw = False ; don't draw yet rts@gsnFrame = False ; don't advance frame yet rts@gsnScale = True ; force text scaling ; these four resources allow the user to stretch the plot size, and ; decide exactly where on the page to draw it. rts@vpHeightF = 0.40 ; Changes the aspect ratio rts@vpWidthF = 0.85 rts@vpXF = 0.10 ; change start locations rts@vpYF = 0.75 ; the plot rts@tiYAxisString = "Pa" ; y-axis label rts@gsnYRefLine = 0. ; reference line rts@gsnXYBarChart = True ; create bar chart rts@gsnAboveYRefLineColor = "red" ; above ref line fill red rts@gsnBelowYRefLineColor = "blue" ; below ref line fill blue ; panel plot only resources rtsP = True ; modify the panel plot rtsP@gsnMaximize = True ; large format rtsP@gsnPanelMainString = "OLR_ANOM: "+season+": "+yStrt+"-"+yLast year = yyyymm/100 ; create individual plots do n=0,neof-1 rts@gsnLeftString = "EOF "+(n+1) rts@gsnRightString = sprintf("%5.1f", eof@pcvar(n)) +"%" plot(n) = gsn_csm_xy (wks,year,eof_ts(n,:),rts) end do gsn_panel(wks,plot,(/neof,1/),rtsP) ; now draw as one plot end