ghcnd_search: Get a cleaned version of GHCND data from a single weather site

Description

This function uses ftp to access the Global Historical Climatology Network daily weather data from NOAA's FTP server for a single weather monitor site. It requires the site identification number for that site and will pull the entire weather dataset for the site. It will then clean this data to convert it to a tidier format and will also, if requested, filter it to a certain date range and to certain weather variables.

Usage

ghcnd_search(stationid, date_min = NULL, date_max = NULL,
  var = "all", refresh = FALSE, ...)

Arguments

stationid

(character) A character string giving the identification of the weather station for which the user would like to pull data. To get a full and current list of stations, the user can use the ghcnd_stations function. To identify stations within a certain radius of a location, the user can use the meteo_nearby_stations function.

date_min

A character string giving the earliest date of the daily weather time series that the user would like in the final output. This character string should be formatted as "yyyy-mm-dd". If not specified, the default is to keep all daily data for the queried weather site from the earliest available date.

date_max

A character string giving the latest date of the daily weather time series that the user would like in the final output. This character string should be formatted as "yyyy-mm-dd". If not specified, the default is to keep all daily data for the queried weather site through the most current available date.

var

A character vector specifying either "all" (pull all available weather parameters for the site) or the weather parameters to keep in the final data (e.g., c("TMAX", "TMIN") to only keep maximum and minimum temperature). Example choices for this argument include:

PRCP: Precipitation, in tenths of millimeters
TAVG: Average temperature, in tenths of degrees Celsius
TMAX: Maximum temperature, in tenths of degrees Celsius
TMIN: Minimum temperature, in tenths of degrees Celsius

A full list of possible weather variables is available in NOAA's README file for the GHCND data (https://www1.ncdc.noaa.gov/pub/data/ghcn/daily/readme.txt). Most weather stations will only have a small subset of all the possible weather variables, so the data generated by this function may not include all of the variables the user specifies through this argument.

refresh

(logical) If TRUE force re-download of data. Default: FALSE

...

In the case of ghcnd additional curl options to pass through to HttpClient. In the case of ghcnd_read further options passed on to read.csv

Value

A list object with slots for each of the available specified weather variables. Each element in the list is a separate time series dataframe with daily observations, as well as flag values, for one of the weather variables. The flag values give information on the quality and source of each observation; see the NOAA README file linked above for more information. Each data.frame is sorted by date, with the earliest date first.

Details

Messages are printed to the console about file path, file last modified time which you can suppress with suppressMessages()

Examples

Run this code

# NOT RUN {
# Search based on variable and/or date
ghcnd_search("AGE00147704", var = "PRCP")
ghcnd_search("AGE00147704", var = "PRCP", date_min = "1920-01-01")
ghcnd_search("AGE00147704", var = "PRCP", date_max = "1915-01-01")
ghcnd_search("AGE00147704", var = "PRCP", date_min = "1920-01-01",
             date_max = "1925-01-01")
ghcnd_search("AGE00147704", date_min = "1920-01-01", date_max = "1925-01-01")
ghcnd_search("AGE00147704", var = c("PRCP","TMIN"))
ghcnd_search("AGE00147704", var = c("PRCP","TMIN"), date_min = "1920-01-01")
ghcnd_search("AGE00147704", var = "adfdf")

# refresh the cached file
ghcnd_search("AGE00147704", var = "PRCP", refresh = TRUE)
# }