R/NLDAS_DL.R

In psavoy/StreamLightUtils: A Utility Package for the StreamLight Package

#' Downloads NLDAS light data
#' @description This function downloads NLDAS incoming shortwave radiation data
#' (w m-2) for a given Latitude and Longitude.
#'
#' @param save_dir The save directory for files to be placed in. For example, "C:/myfolder
#' @param Site_ID The site ID, for example "NC_NHC"
#' @param Lat The site Latitude
#' @param Lon The site Longitude
#' @param startDate The starting date for the download (YYYY-MM-DD)
#'
#' @return Returns a time series of incoming shortwave solar radiation from the start
#' date to the most recent available data
#' @export

#===============================================================================
#Function for downloading NLDAS light data via data rods
#https://disc.gsfc.nasa.gov/information/tools?title=Hydrology%20Data%20Rods
#Created 11/27/2017
#===============================================================================
NLDAS_DL <- function(save_dir, Site_ID, Lat, Lon, startDate){
  #The initial string to build the URL
    http_string <- paste("https://hydro1.gesdisc.eosdis.nasa.gov/daac-bin/access/timeseries.cgi?variable=NLDAS:NLDAS_FORA0125_H.002:DSWRFsfc")

  #Separating the date information
    start_split <- strsplit(startDate, "-")[[1]]

  #Build individual components of the url
    location_string <- paste0("&location=GEOM:POINT(", Lon, ",%20", Lat, ")")
    start_string <- paste0("&startDate=", start_split[1], "-", start_split[2], "-", 
      start_split[3], "T00")
    
  #Generating the URL
    url <-paste0(http_string, location_string, start_string, "&type=asc2")

  #Downloading the data
    destfile <- paste(save_dir, "/", Site_ID, "_NLDAS.asc", sep = "")

  #Error catch in case the page is inaccessible. A little inelegant at present...
    try_result <- try(download.file(url, destfile, method = "libcurl"), silent = FALSE)

    if(class(try_result) == "try-error") {file.remove(destfile)}

} #End DL_NLDAS function