snotelr functionality

Introduction

The SNOTEL network is composed of over 800 automated data collection sites located in remote, high-elevation mountain watersheds in the western U.S. They are used to monitor snowpack, precipitation, temperature, and other climatic conditions. The data collected at SNOTEL sites are transmitted to a central database. This package queries this centralized database to provide easy access to these data and additional seasonal metrics of snow accumulation (snow phenology).

Downloading site meta-data

The SNOTEL network consists of a vast number of observation sites, all of them listed together with their meta-data on the SNOTEL website. The snotel_info() function allows you to query this table and import it as a neat table into R. Some of the meta-data, in particular the site id (site_id), you will need of you want to download the data for a site. You can save this table to disk using the path variable to specify a location on your computer where to store the data as a csv. If this parameter is missing the data is returned as an R variable.

# download and list site information
site_meta_data <- snotel_info()
head(site_meta_data)

Downloading site data

If you downloaded the meta-data for all sites you can make a selection using either geographic coordinates, or state columns. For the sake of brevity I’ll only query data for one site using its site_id below. By default the data, reported in imperial values, are converted to metric measurements.

# downloading data for a random site
snow_data <- snotel_download(
  site_id = 670,
  internal = TRUE
  )

# show the data
head(snow_data)

# A plot of snow accummulation through the years
plot(as.Date(snow_data$date),
     snow_data$snow_water_equivalent,
     type = "l",
     xlab = "Date",
     ylab = "SWE (mm)"
    )

Calculating snow phenology from downloaded data or data frames

Although the main function of the package is to provide easy access to the SNOTEL data a function snotel_phenology() is provided to calculate seasonal metrics of snow deposition.

# calculate snow phenology
phenology <- snotel_phenology(snow_data)

# subset data to the first decade of the century
snow_data_subset <- subset(snow_data, as.Date(date) > as.Date("2000-01-01") &
                             as.Date(date) < as.Date("2010-01-01"))

# plot the snow water equivalent time series
plot(as.Date(snow_data_subset$date),
     snow_data_subset$snow_water_equivalent,
     type = "l",
     xlab = "Date",
     ylab = "SWE (mm)"
  )

# plot the dates of first snow accumulation as a red dot
points(phenology$first_snow_acc,
       rep(1,nrow(phenology)),
       col = "red",
       pch = 19,
       cex = 0.5
      )

A list of all provided snow phenology statistics is provided below.

Value	Description
year	The year in which the an event happened
first_snow_melt	day of first full snow melt (in DOY)
cont_snow_acc	start of continuous snow accumulation / retention (in DOY)
last_snow_melt	day on which all snow melts for the remaining year (in DOY)
first_snow_acc	day on which the first snow accumulates (in DOY)
max_swe	maximum snow water equivalent value during a given year (in mm)
max_swe_doy	day on which the maximum snow water equivalent value is reached (in DOY)

snotelr functionality

Koen Hufkens

2024-11-20

Introduction

Downloading site meta-data

Downloading site data

Calculating snow phenology from downloaded data or data frames

Reference