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linguist/samples/NCL/mcsst_1.ncl
2015-07-09 07:17:01 -07:00

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;*****************************************************
; mcsst_1.ncl
;
; Concepts illustrated:
; - Plotting NAVO MCSST data
; - Using fbindirread to read in fortran binary data
; - Converting "byte" data to "float"
; - Adding meta data (attributes and coordinates) to a variable
; - Adding gray to an existing color map
; - Spanning all but the last two colors in a color map for contour fill
; - Drawing raster contours
;
;*****************************************************
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
;***************************************
; type of data available on file
;***************************************
; ipar=0 Weekly Binned Sea Surface Temperature
; ipar=1 Number of Points in Bin
; ipar=2 Weekly Binned Sea Surface Temperature Anomaly
; ipar=3 Interpolated Sea Surface Temperature
; ipar=4 Interpolated Sea Surface Temperature Anomaly
;***************************************
begin
ipar = 3
fname = "2001311d18N16.dat"
tmp = fbindirread(fname,ipar,(/1024,2048/),"byte")
;***************************************
; convert to float and then change to true SST
;***************************************
xslope = 0.15
if(ipar.eq.4.or.ipar.eq.2)then ; anom has different intercept
yint = -20.0
end if
if(ipar.eq.3.or.ipar.eq.0)then
yint = -3.0
end if
sst = new((/1024,2048/),"float") ; create float var
sst = tmp*xslope+yint ; convert to float
delete(tmp) ; delete unecessary array
;***************************************
; assign missing values. The original missing value was zero, but since it was
; not assigned in NCL, it was not recognized. The new missing values are
; listed below. These will be changed later.
;***************************************
if(ipar.eq.4)then
sst@_FillValue = -20
end if
if(ipar.eq.3.or.ipar.eq.0)then
sst@_FillValue = -3
end if
;***************************************
; create coordinate variables
;***************************************
nlat = 1024
dy = 180./nlat
lat = (90. -(ispan(0,1023,1)*dy))-dy/2
lat!0 = "lat"
lat&lat = lat
lat@units = "degrees_north"
nlon = 2048
dx = 360./nlon
lon = (ispan(0,2047,1)*dx)+dx/2-180. ; note -180. added by sjm to align
lon!0 = "lon"
lon&lon = lon
lon@units = "degrees_east"
;***************************************
; fill out the netCDF data model
;***************************************
sst!0 = "lat" ; name dimensions
sst!1 = "lon" ; ditto
sst = sst(::-1,:) ; reverse lat orientation
sst@long_name = "NAVO MCSST" ; assign long_name
sst@units = "deg C" ; assign units
sst&lat = lat ; assign lat cv
sst&lon = lon ; assign lon cv
sst@_FillValue = -999. ; assign missing value
;***************************************
; get year and day from filename
;***************************************
res = True ; plot mods desired
title = stringtochar(fname) ; parse file name to get date
year = title(0:3)
jday = title(4:6)
res@gsnCenterString = year+" "+jday ; create center string
;***************************************
; create plot
;***************************************
wks = gsn_open_wks("ps","mcsst") ; open workstation (plot destination)
gsn_define_colormap(wks,"BlGrYeOrReVi200") ; choose colormap
;
; This will not be necessary in V6.1.0 and later. Named colors can
; be used without having to first add them to the color map.
;
d = NhlNewColor(wks,0.8,0.8,0.8) ; add gray to colormap
res@cnFillOn = True ; turn on color
res@gsnSpreadColors = True ; use full range of colormap
res@gsnSpreadColorStart = 2 ; start at color 2
res@gsnSpreadColorEnd = -3 ; don't use added gray
res@cnLinesOn = False ; no contour lines
res@cnFillDrawOrder = "PreDraw" ; draw contours before continents
res@gsnMaximize = True ; maximize plot
; For a grid this size, it is better to use raster mode. It will be
; significantly faster, and will not go over NCL's 16mb default plot size.
res@cnFillMode = "RasterFill" ; turn on raster mode
plot = gsn_csm_contour_map_ce(wks,sst,res) ; contour the variable
end