meteo_nearby_stations: Find weather monitors near locations

Description

This function inputs a dataframe with latitudes and longitudes of locations and creates a dataframe with monitors within a certain radius of those locations. The function can also be used, with the limit argument, to pull a certain number of the closest weather monitors to each location. The weather monitor IDs in the output dataframe can be used with other rnoaa functions to pull data from all available weather stations near a location (e.g., meteo_pull_monitors).

Usage

meteo_nearby_stations(lat_lon_df, lat_colname = "latitude", lon_colname = "longitude", station_data = ghcnd_stations()[[1]], var = "all", year_min = NULL, year_max = NULL, radius = NULL, limit = NULL)

Arguments

lat_lon_df

A dataframe that contains the latitude, longitude, and a unique identifier for each location (id). For an example of the proper format for this dataframe, see the examples below. Latitude and longitude must both be in units of decimal degrees. Southern latitudes and Western longitudes should be given as negative values.

lat_colname

A character string giving the name of the latitude column in the lat_lon_df dataframe.

lon_colname

A character string giving the name of the longitude column in the lat_lon_df dataframe.

station_data

The output of ghcnd_stations()[[1]], which is a current list of weather stations available through NOAA for the GHCND dataset. The format of this is a dataframe with one row per weather station. Latitude and longitude for the station locations should be in columns with the names "latitude" and "longitude", consistent with the output from ghcnd_stations()[[1]]. To save time, run the ghcnd_stations call and save the output to an object, rather than rerunning the default every time (see the examples in meteo_nearby_stations).

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 (http://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.

year_min

A numeric value giving the earliest year from which you ultimately want weather data (e.g., 2013, if you only are interested in data from 2013 and later).

year_max

A numeric value giving the latest year from which you ultimately want weather data.

radius

A numeric vector giving the radius (in kilometers) within which to search for monitors near a location.

limit

An integer giving the maximum number of monitors to include for each location. The [x] closest monitors will be kept. Default is NULL (pull everything available, within the radius if the radius is specified).

Value

A list containing dataframes with the sets of unique weather stations within the search radius for each location. Site IDs for the weather stations given in this dataframe can be used in conjunction with other functions in the rnoaa package to pull weather data for the station. The dataframe for each location includes:

id: The weather station ID, which can be used in other functions to pull weather data from the station;
name: The weather station name;
latitude: The station's latitude, in decimal degrees. Southern latitudes will be negative;
longitude: The station's longitude, in decimal degrees. Western longitudes will be negative;
distance: The station's distance, in kilometers, from the location.

Details

Great circle distance is used to determine whether a weather monitor is within the required radius.

Examples

Run this code

## Not run: 
# 
# station_data <- ghcnd_stations()[[1]] # Takes a while to run
# 
# lat_lon_df <- data.frame(id = c("sydney", "brisbane"),
#                          latitude = c(-33.8675, -27.4710),
#                          longitude = c(151.2070, 153.0234))
# nearby_stations <-  meteo_nearby_stations(lat_lon_df = lat_lon_df,
#                     station_data = station_data, radius = 10)
# 
# miami <- data.frame(id = "miami", latitude = 25.7617, longitude = -80.1918)
# 
# # Get all stations within 50 kilometers
# meteo_nearby_stations(lat_lon_df = miami, station_data = station_data,
#                       radius = 50, var = c("PRCP", "TMAX"),
#                       year_min = 1992, year_max = 1992)
# # Get the closest 10 monitors
# meteo_nearby_stations(lat_lon_df = miami, station_data = station_data,
#                       limit = 10, var = c("PRCP", "TMAX"),
#                       year_min = 1992, year_max = 1992)
# ## End(Not run)

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