R/get_met_gdas1.R

In rich-iannone/SplitR: Use the HYSPLIT model from inside R

#' Get GDAS1 meteorology data files
#'
#' Downloads GDAS1 meteorology data files from the NOAA FTP server and saves
#' them to a specified folder. Files can be downloaded by specifying a list of
#' filenames (in the form of `"gdas1.{month-abbrev}{year-2}.w{wk-num}"`).
#'
#' @inheritParams hysplit_trajectory
#' @param path_met_files A full directory path to which the meteorological data
#'   files will be saved.
#'   
#' @export
get_met_gdas1 <- function(days,
                          duration,
                          direction,
                          path_met_files) {
  
  # Determine the minimum date (as a `Date`) for the model run
  if (direction == "backward") {
    min_date <- 
      (lubridate::as_date(days[1]) - (duration / 24)) %>%
      lubridate::floor_date(unit = "day")
  } else if (direction == "forward") {
    min_date <- 
      (lubridate::as_date(days[1])) %>%
      lubridate::floor_date(unit = "day")
  }
  
  # Determine the maximum date (as a `Date`) for the model run
  if (direction == "backward") {
    max_date <- 
      (lubridate::as_date(days[length(days)])) %>%
      lubridate::floor_date(unit = "day")
  } else if (direction == "forward") {
    max_date <- 
      (lubridate::as_date(days[length(days)]) + (duration / 24)) %>%
      lubridate::floor_date(unit = "day")
  }
  
  met_days <- 
    seq(min_date, max_date, by = "1 day") %>% 
    lubridate::day()
  
  # "en_US.UTF-8" is not a valid locale for windows.
  os_for_locale <- get_os()
  if(os_for_locale == "win"){
    month_names <- 
      seq(min_date, max_date, by = "1 day") %>%
      lubridate::month(label = TRUE, abbr = TRUE, locale = Sys.setlocale("LC_TIME", "English"))  %>%
      as.character() %>%
      tolower()
  } else {
    month_names <- 
      seq(min_date, max_date, by = "1 day") %>%
      lubridate::month(label = TRUE, abbr = TRUE, locale = "en_US.UTF-8")  %>%
      as.character() %>%
      tolower()
  }
  
  met_years <- 
    seq(min_date, max_date, by = "1 day") %>%
    lubridate::year() %>% 
    substr(3, 4)
  
  # Only consider the weeks of the month we need:
  #.w1 - days 1-7
  #.w2 - days 8-14
  #.w3 - days 15-21
  #.w4 - days 22-28
  #.w5 - days 29 - rest of the month 
  
  met_week <- ceiling(met_days / 7)
  
  files <- paste0("gdas1.", month_names, met_years, ".w", met_week) %>% unique()
  
  get_met_files(
    files = files,
    path_met_files = path_met_files,
    ftp_dir = "ftp://arlftp.arlhq.noaa.gov/archives/gdas1"
  )
  
}