Apparently NOAA and the NWS use a non-traditional projection for some of their rainfall data and don't offer a lot of help in terms of projecting it to a traditional format for other users. I've had a bit of success in getting the raster to overlay for part of the United States but it still isn't quite right.
I'm hoping someone can help me decipher what I am missing and correct the projection of this data.
You can find more information of this data here: https://polyploid.net/blog/?p=216 https://water.weather.gov/precip/download.php
library(tidyverse)
library(raster)
library(rgdal)
library(sp)
setwd("C:/Users/MPE_Data/")
file_list <- list.files("201809")
grib0<-raster::brick("201809//ST4_2018091307_24h.nc", varname="APCP_SFC")[[1]]
grib0@crs
crs(grib0) <- "+proj=longlat +a=6371200 +b=6371200 +no_defs"
crs(grib0) <- "+proj=stere +lat_0=90 +lat_ts=60 +lon_0=-105 +x_0=0 +y_0=0 +a=6371200 +b=6371200 +units=m +no_defs"
us_shp <- rgdal::readOGR("C:/Users/cb_2017_us_state_500k/US_clipped.shp")
shp <- rgdal::readOGR("C:/Users/nc_sc_counties_wgs1984.shp")
wgs<-"+proj=longlat +datum=WGS84 +ellps=WGS84 +no_defs"
wgsraster <- projectRaster(grib0, crs=wgs)
plot(wgsraster)
shp <- spTransform(shp, CRS(wgs))
us_shp <- spTransform(us_shp, CRS(wgs))
plot(shp,add=TRUE)
plot(us_shp,add=TRUE)
I couldn't find your exact map but here is an example using recent precipitation data. You don't need to assign a CRS as the netCDF file already has a CRS associated with it, you can simply
projectRaster
. Also the NOAA website has the option to download to geoTIFF which I would recommend if you are more comfortable with that.+proj=stere +lat_0=90 +lat_ts=60 +lon_0=-105 +x_0=0 +y_0=0 +a=6371200 +b=6371200 +units=m +no_defs
Note that the maximum value of
rs
changed from 7.8 to 7.0 due to the bilinear interpolation method used inprojectRaster
. You need to consider whether you require bilinear or nearest neighbour interpolation and if you need to be specific about the output raster resolution and extent I would suggest supplying a model raster for theto
argument.Edited to incorporate @Robert Hijmans' suggestion.