Creating raster layer from NetCDF in OPeNDAP DODs (Distributed Oceanographic Data Systems) format

Question

I am trying to access NetCDF files from Simple Ocean Data Assimilation (SODA) 2.2.4. I want to download them as raster layers, with temp, year, depth, lat, and lon data.

The files are in DODs (Distributed Oceans Data Systems)/OPeNDAP because they are too big to download as a netcdf file. I haven't used this format before, as I've always been able to just download the .nc files. On the site, it says I should be able to just use this link as if it were a .nc file in R script in order to convert to a raster layer and download. However, when I try to do this, it fails. However, I can view attributes about the file in R, as shown below.

url_grid <- "http://iridl.ldeo.columbia.edu/SOURCES/.CARTON-GIESE/.SODA/.v2p2p4/.temp/time/%28Jan%201953%29%28Dec%201979%29RANGEEDGES/lat/%280N%29%2889.5N%29RANGEEDGES/lon/%28-200E%29%2820E%29RANGEEDGES/dods"

nc <- nc_open(url_grid)

nc

File http://iridl.ldeo.columbia.edu/SOURCES/.CARTON-GIESE/.SODA/.v2p2p4/.temp/time/%28Jan%201953%29%28Dec%201979%29RANGEEDGES/lat/%280N%29%2889.5N%29RANGEEDGES/lon/%28-200E%29%2820E%29RANGEEDGES/dods (NC_FORMAT_CLASSIC):

     1 variables (excluding dimension variables):
        float temp[lon,lat,depth,time]   
            pointwidth: 1
            missing_value: -9.98999971057742e+33
            standard_name: sea_water_temperature
            units: Celsius_scale
            long_name: TEMPERATURE

     4 dimensions:
        depth  Size:40
            gridtype: 0
            units: meters
        lat  Size:179
            standard_name: latitude
            pointwidth: 0.5
            gridtype: 0
            units: degree_north
        lon  Size:440
            standard_name: longitude
            pointwidth: 0.5
            gridtype: 0
            units: degree_east
        time  Size:324
            standard_name: time
            pointwidth: 1
            calendar: 360
            gridtype: 0
            units: months since 1960-01-01

    1 global attributes:
        Conventions: IRIDL

#This function reads out data from a typical netcdf I have downloaded (I've used this and it works great for .nc files)
get.soda <- function(file){

  soda.info <- nc_open(file)
  name.soda.sizes <- sapply(soda.info$var$temp$dim, function(x)x$name)
  soda.sizes <- soda.info$var$temp$size
  dim.units <- sapply(soda.info$var$temp$dim, function(x)x$units)
  print(dim.units)
  stopifnot(grepl("months since ", dim.units[4])) # make sure time is in correct units and in right place
  names(soda.sizes) <- name.soda.sizes
  ntime <- soda.sizes["time"]
  ndepth <- soda.sizes["depth"]

  soda.time0 <- soda.info$var$temp$dim[[4]]$vals
  ref.date <- as.Date(gsub("months since ", "", dim.units[4]))
  start.before.ref <- grepl("-", soda.time0[1]) # is the first date before ref.date?
  n.month.before <- ceiling(abs(soda.time0[1])) + as.integer(start.before.ref)
  start.increment <- ifelse(start.before.ref, "-1 month", "1 month")
  time.start <- rev(seq.Date(ref.date, by=start.increment, length.out=n.month.before))[1]
  soda.time <- seq.Date(time.start, by="1 month", length.out=ntime)

  soda <- brick(file)
  names(soda) <- soda.time


  return(soda)

}

get.soda(url_grid)
[1] "degree_east"             "degree_north"           
[3] "meters"                  "months since 1960-01-01"

#I get the following error message:

Error in .local(.Object, ...) : 

Error in .rasterObjectFromFile(x, objecttype = "RasterBrick", ...) : 
  Cannot create a RasterLayer object from this file. (file does not exist)

The file does not exist on my computer, but should exist at this link? Help?

Creating raster layer from NetCDF in OPeNDAP DODs (Distributed Oceanographic Data Systems) format

0 Answers0