[ncl-talk] Spatial trend plot for JJAS season
Buzan, Jonathan
jbuzan at purdue.edu
Thu Apr 21 09:24:02 MDT 2022
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<mailto: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<http://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)+"<mailto:;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
_______________________________________________
ncl-talk mailing list
ncl-talk at mailman.ucar.edu<mailto:ncl-talk at mailman.ucar.edu>
List instructions, subscriber options, unsubscribe:
https://mailman.ucar.edu/mailman/listinfo/ncl-talk
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.ucar.edu/pipermail/ncl-talk/attachments/20220421/715127ed/attachment.html>
More information about the ncl-talk
mailing list