[ncl-talk] Spatial trend plot for JJAS season
Lekshmi M S
lekshmiragal at gmail.com
Thu Apr 21 09:50:08 MDT 2022
Thanks a lot, I'll check it out.
On Thu, Apr 21, 2022 at 8:54 PM Buzan, Jonathan <jbuzan at purdue.edu> wrote:
> Hi Lekshmi,
>
> The month_to_annual function can be found in the:
>
> $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl
>
> I recommend looking at how the function behaves, and then creating your
> own function that mimics the month_to_annual but specifically for the
> season that you are focused on.
>
> For example, a 3D variable, T(time,lat,lon) uses the rankx.eq.3:
> contributed.ncl
>
> if (rankx.eq.3) then
> ny = dimx(1) ; nlat
> mx = dimx(2) ; mlon
> nyr = -1
> xAnnual= new ( (/nyrs,ny,mx/), typeof(x), getFillValue(x))
> ; contributed.ncl
> do nt=0,ntim-1,NMOS
> xTemp = x(nt:nt+NMOS1,:,:) ; cleaner code only
> nyr = nyr+1
>
> if (opt.eq.0) then
> xAnnual(nyr,:,:) = dim_sum_n ( xTemp, 0 )
> else
> xAnnual(nyr,:,:) = dim_avg_n ( xTemp, 0 )
> end if
>
> nMsg = 0 ; number of missing for
> current year (nyr)
> if (isatt(x,"_FillValue")) then
> nMsg = num (ismissing(xTemp) ) ; for all grid points
> end if
>
> if (nMsg.gt.0) then
> nGood = dim_num_n(.not.ismissing(xTemp), 0 )
> ; (lat,lon)
> xAnnual(nyr,:,:) = mask( xAnnual(nyr,:,:), nGood.ge.nmos,
> True) ; ?False
> print("month_to_annual: some grid points have missing data:
> nt="+nt \
> +" nyr="+nyr+" num(nGood)="+num(nGood.gt.0))
> end if
> end do
>
> copy_VarAtts (x, xAnnual)
> xAnnual at NCL = "month_to_annual"
> xAnnual!0 = "year"
> copy_VarCoords_skipDim0 (x, xAnnual)
> return(xAnnual)
> end if
>
>
> Cheers,
> -Jonathan
>
>
>
> On Apr 21, 2022, at 16:52, Lekshmi M S via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
> I would like to modify the following script to spatially plot the JJAS
> precipitation trend plot for 70years. Instead of using "month_to_annual", I
> think I have to use "month_to _season" here. But JJAS is not defined as a
> season here. Please help me to do this for JJAS months.
>
> ;*************************************************
> ; regress_4.ncl
> ;
> ; Concepts illustrated:
> ; - Drawing color-filled contours over a cylindrical equidistant map
> ; - Calculating the regression coefficient (slope) at each grid point
> ; - Copying attributes from one variable to another
> ;
> ;*************************************************
> ;
> ; 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
>
> ;************************************************
> ; Specify geographical region and time span (year-month start and end
> ;************************************************
>
> latS = -90
> latN = 90
> lonL = 0
> lonR = 360
>
> ymStrt = 195101
> ymLast = 201012
>
> pltTitle = "Globe: "+(ymStrt/100)+"-"+(ymLast/100)
>
> ;************************************************
> ; Read from netCDF file: variable is type short...unpack
> ;************************************************
> diri = "./"
> fili = "air.sig995.mon.mean.nc"
> f = addfile(diri+fili,"r")
>
> YYYYMM = cd_calendar( f->time, -1)
>
> iStrt = ind(YYYYMM.eq.ymStrt)
> iLast = ind(YYYYMM.eq.ymLast)
>
> x = short2flt( f->air(iStrt:iLast,{latS:latN},{lonL:lonR}) )
>
> x = x-273.15
> x at units= "degC"
>
> printVarSummary(x) ; [time| 720]x[lat| 91]x[lon| 180]
>
> yyyymm = cd_calendar(x&time, -1)
> yyyy = yyyymm/100
>
> dimx = dimsizes(x)
> ntim = dimx(0) ; all years and months
> nlat = dimx(1)
> mlon = dimx(2)
>
> year = ispan(yyyy(0), yyyy(ntim-1), 1)
> nyrs = dimsizes(year)
>
> ;************************************************
> ; Areal averages: cos(lat) is good enough
> ;************************************************
>
> xann = month_to_annual(x , 1) ; [year| 60]x[lat| 91]x[lon| 180]
> xann&year = year
> printVarSummary(xann)
>
> ;************************************************
> ; Calculate the regression coefficients (slopes)
> ;************************************************
> rc = regCoef(year,xann(lat|:,lon|:,year|:))
>
> rc at long_name = "Trend"
> rc at units = xann at units+"/year"
> copy_VarCoords(xann(0,:,:), rc) ; copy lat,lon coords
>
> printVarSummary(rc)
>
> ;************************************************
> ; for illustration: change units to degC/period-used
> ;************************************************
> rc = rc*nyrs ; (C/year)*(nyrs)
> rc at units = "degC/"+nyrs+"_year"
>
> ;************************************************
> ; plotting parameters
> ;************************************************
> wks = gsn_open_wks("png","regress") ; send graphics to PNG file
>
> res = True
> res at gsnMaximize = True ; make large
>
> res at cnFillOn = True ; turn on color
> res at cnLinesOn = False ; turn off contour lines
> res at cnLineLabelsOn = False ; turn off contour line labels
> ;;res at cnFillMode = "RasterFill"
>
> res at cnLevelSelectionMode = "ManualLevels" ; set manual contour levels
> res at cnMinLevelValF = -2.0 ; set min contour level
> res at cnMaxLevelValF = 2.0 ; set max contour level
> res at cnLevelSpacingF = 0.2 ; set contour interval
>
> res at mpFillOn = False ; turn off default background gray
> ;res at mpCenterLonF = 180
>
> res at gsnCenterString = year(0)+" <;setmanualcontourlevelsres at cnMinLevelValF=-2.0;setmincontourlevelres at cnMaxLevelValF=2.0;setmaxcontourlevelres at cnLevelSpacingF=0.2;setcontourintervalres at mpFillOn=False;turnoffdefaultbackgroundgray;res at mpCenterLonF=180res at gsnCenterString=year(0)+>-"+year(nyrs-1)
>
> res at tiMainString = "20th Century Reanalysis: sig995" ; fili
> plot = gsn_csm_contour_map_ce(wks,rc,res)
> end
>
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