Example 1 : Regular Grid

• two-dimensional fields on a regular longitude,latitude grid are retrieved from binary files
• they are then written to a new netcdf file using NCTiles.write()

This example illustrates the use of either NCDatasets.jl or NetCDF.jl as the backend.

using NCTiles
import NCTiles: NCDatasets, NetCDF, Dates

File Paths

inputs=NCTiles.NCTILES_TESTCASES
NCTiles.ensure_testcases_installed()

outputs = joinpath(tempdir(),"NCTILES_TESTCASES_OUTPUT/")
if ~ispath(outputs); mkpath(outputs); end

selectfields = ["ETAN"]
indir = joinpath(inputs,"diags_interp",selectfields[1])
fnames = joinpath.(Ref(indir),filter(x -> occursin(".data",x), readdir(indir)))

savedir = joinpath(outputs,"ex1")
if ~ispath(savedir); mkpath(savedir); end

Grid specifications & Metadata

prec = Float32
README = ["File created by","example 1 of NCTiles.jl","on "*string(Dates.now())]
lon=-179.75:0.5:179.75; lat=-89.75:0.5:89.75;
n1,n2 = (length(lon),length(lat))
tim_units = "days since 1992-01-01"
tim = vec([14.0 45.0 74.0])
longname = "Surface Height Anomaly"
units = "m"

"m"

1. Using NCDatasets.jl As The Backend

Define Dimensions as NCvars

dims = [NCvar("lon_c","degrees_east",size(lon),lon,Dict("long_name" => "longitude"),NCDatasets),
        NCvar("lat_c","degrees_north",size(lat),lat,Dict("long_name" => "latitude"),NCDatasets),
        NCvar("tim",tim_units,Inf,tim,Dict(("long_name" => "tim","standard_name" => "time")),NCDatasets)
        ]

3-element Vector{NCvar}:
 NCvar("lon_c", "degrees_east", (720,), -179.75:0.5:179.75, Dict("long_name" => "longitude"), NCDatasets)
 NCvar("lat_c", "degrees_north", (360,), -89.75:0.5:89.75, Dict("long_name" => "latitude"), NCDatasets)
 NCvar("tim", "days since 1992-01-01", Inf, [14.0, 45.0, 74.0], Dict("long_name" => "tim", "standard_name" => "time"), NCDatasets)

Define Variable Array as BinData

fielddata = BinData(fnames,prec,(n1,n2))
field = NCvar(selectfields[1],units,dims,fielddata,Dict("long_name" => longname),NCDatasets)

NCvar("ETAN", "m", NCvar[NCvar("lon_c", "degrees_east", (720,), -179.75:0.5:179.75, Dict("long_name" => "longitude"), NCDatasets), NCvar("lat_c", "degrees_north", (360,), -89.75:0.5:89.75, Dict("long_name" => "latitude"), NCDatasets), NCvar("tim", "days since 1992-01-01", Inf, [14.0, 45.0, 74.0], Dict("long_name" => "tim", "standard_name" => "time"), NCDatasets)], BinData(["/home/runner/.julia/artifacts/4c36bdda8c1f8388b7f6de8da17d965dab33431e/nctiles-testcases-0.1/diags_interp/ETAN/ETAN.0000000732.data", "/home/runner/.julia/artifacts/4c36bdda8c1f8388b7f6de8da17d965dab33431e/nctiles-testcases-0.1/diags_interp/ETAN/ETAN.0000001428.data", "/home/runner/.julia/artifacts/4c36bdda8c1f8388b7f6de8da17d965dab33431e/nctiles-testcases-0.1/diags_interp/ETAN/ETAN.0000002172.data"], Float32, (720, 360), 1), Dict("long_name" => "Surface Height Anomaly"), NCDatasets)

Create the NetCDF file and populate with dimensions and variable

write(field,joinpath(savedir,"ex1_NCDatasets.nc"),README=README)

closed Dataset

2. Using NetCDF.jl As The Backend

Define Dimensions as NCvars

dims = [NCvar("lon_c","degrees_east",size(lon),lon,Dict("long_name" => "longitude"),NetCDF),
        NCvar("lat_c","degrees_north",size(lat),lat,Dict("long_name" => "latitude"),NetCDF),
        NCvar("tim",tim_units,Inf,tim,Dict(("long_name" => "time","standard_name" => "time")),NetCDF)
        ]

3-element Vector{NCvar}:
 NCvar("lon_c", "degrees_east", (720,), -179.75:0.5:179.75, Dict("long_name" => "longitude"), NetCDF)
 NCvar("lat_c", "degrees_north", (360,), -89.75:0.5:89.75, Dict("long_name" => "latitude"), NetCDF)
 NCvar("tim", "days since 1992-01-01", Inf, [14.0, 45.0, 74.0], Dict("long_name" => "time", "standard_name" => "time"), NetCDF)

Define Variable Array as BinData

fielddata = BinData(fnames,prec,(n1,n2))
field = NCvar(selectfields[1],units,dims,fielddata,Dict("long_name" => longname),NetCDF)

write(field,joinpath(savedir,"ex1_NetCDF.nc"),README=README)

Note: the write function is a shorthand for

# Create the NetCDF file and populate with dimension and field info, as well as dimension data
ncfile,fldvar,dimlist = createfile(joinpath(savedir,"ex1_NetCDF.nc"),field,README)

# Add field data
addData(fldvar,field)

# Close the file-  only needed for NetCDF v < 0.10
finalize(ncfile)

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