Western U.S. NRCS data
Collection of environmental data, including met and soils data, from NRCS, Ameriflux, and other research stations and its processing for analysis is covered here.
Start date: 25 Jan, 2010
- Gather continuous measurements of soil moisture, soil temperature, weather/climate, snowpack dynamics, and metrics of soil biological activity for western U.S. mountain sites.
- Quantify spatial variability (by elevation, topography, lat/lon) in climate, snowpack dynamics, SM/ST.
- Quantify inter-annual variability in climate, snowpack dynamics, SM/ST.
- Assess the relationships between spatial or inter-annual variability in SM/ST, climate, and snowpack dynamics among sites.
National Water and Climate Center - SNOTEL, SCAN, and Snow Course data
Most data, including SNOTEL (mountain) and SCAN (lowland) automated station data comes from the National Water and Climate Center. This division of the USDA's Natural Resources Conservation Service runs the Snow Survey (Snow Courses), SNOTEL network, and SCAN network and provides a few online interfaces for accessing this data.
- The NWCC station inventory lists SCAN/SNOTEL sites by state and element (sensor or data type). This provides good inventory and indexing data.
- Individual station siteslike this one allow generation of element (sensor or data) reports for particular time periods, including historical periods.
- The Snow Course data portalallows access to historical snow measurements. Many of these measurements extend back to the 1950's or earlier, and many snow courses are still measured today. They provide calibration data for adjacent SNOTEL stations.
Other (potentially useful) sites
SNOTEL and SCAN raw data files
Files are downloaded as .csv (usually), and are often edited using various text editing and data file handling tools.
Soil station inventory files
Files are downloaded from the NWCC station inventory site. The original column headers are:
Several inventory files, selected using the dropdowns, are useful:
- Selecting precipitation accumulation gives pretty much all SNOTEL and SCAN sites.
- Selecting soil moisture and temperature gives a file containing only sites with soil sensor profiles (SCAN and SNOTEL).
These inventory files have been put into a master spreadsheet that keeps track of sites and the data collected for them (see the inventory directory).
Hourly SM/ST data
Files downloaded from individual station sites by specifying download of hourly wateryear data for SM/ST sensors. One file for each year that the sensors have been in operation must be downloaded.
Fields in these files: \^ Variable name \^ Measurement \^ Units/Format \^ Measurement period \^ | Site Id | Site identification number | integer | - | | Date | Date | yyyy-mm-dd | - | | Time | Time of measurement | hh:mm | - | | SMS.I-1:-2(-8, -20) | Soil moisture @ -2 in (or -8in, -20in) | VWC (%) | hourly average | | STO.I-1:-2(-8, -20) | Soil moisture @ -2 in (or -8in, -20in) | °C | hourly average | | STO.I-1:0 or STO.I-2:0 | Calculated values are sometimes present at odd depths (0) or marked with I-2 (ignore these) |||
All datafiles for UT, ID SNOTEL sites with soil profiles.
Daily summaries - all sensors
Files downloaded from individual station sites by specifying download of daily wateryear data for all sensors. One file for each year that the sensors have been in operation must be downloaded. Instantaneous measurements in these files are for 12AM (data is the same as 12am files - see below). These files include daily calculated temperatures (TMAX, TMIN, TAVG).
Fields in these files: \^ Variable name \^ Measurement \^ Units/Format \^ Measurement period \^ | Site Id | Site identification number | integer | - | | Date | Date | yyyy-mm-dd | - | | Time | Time of measurement | hh:mm | - | | WTEQ.I-1 | Snow water equivalent (pillow) | inches | Instantaneous | | PREC.I-1 | Accumulated Precipitation | inches | Instantaneous | | TOBS.I-1 | Observed temperature | °C | Instantaneous | | TMAX.D-1 | Maximum daily temperature | °C | Calculated daily | | TMIN.D-1 | Minimum daily temperature | °C | Calculated daily | | TAVG.D-1 | Average daily temperature | °C | Calculated daily | | SNWD.I-1 | Snow depth (Judd sensor) | inches | Instantaneous | | SMS.I-1:-2(-8, -20) | Soil moisture @ -2 in (or -8in, -20in) | VWC (%) | Instantaneous | | STO.I-1:-2(-8, -20) | Soil temp @ -2 in (or -8in, -20in) | °C | Instantaneous | | SAL.I-1:-2(-8, -20) | Soil salinity @ -2 in (or -8in, -20in) | grams/l | Instantaneous | | RDC.I-1:-2(-8, -20) | Real dielectric constant (each soil sensor) | unitless | Instantaneous | | BATT.I-1 | Battery voltage | voltage | Instantaneous | | STO.I-1:0 or STO.I-2:0 | Calculated values are sometimes present at odd depths (0) or marked with I-2 (ignore these) ||| | WTEQ.I-2 | Some sites have additional (backup?) measurements - Ignore these |||
Note that the calculated values (for temperature) are suspect prior to hourly recording of measurements (see note below).
All datafiles for AZ. CO, ID, MT, NM, NV, UT, WY SNOTEL sites.
Instantaneous measurement files
Instantaneous measurements for individual or all sensors can be downloaded hourly, or for every third hour (12AM, 3AM...6PM, 9PM). These contain instantaneous measurements for any sensors chosen (including all) at the time period chosen. They do not include summary data (TMIN, TMAX, TAVG) like the files above).
NOTE: At many snotel sites, true hourly measurements did not begin until well after the site was established (mid to late 90's at many).
Sensors and calibrations
Soil sensors at these sites are Stevens Hydra-Probe sensors. Some appear to be the analog version of the sensor which measures soil moisture, temperature, and electrical conductivity. Some may be the digital version (HydraProbe II), but I'm not sure about this.SM/ST sensors are generally located at 2, 8 and 20 inch depths (5, 20, 50cm), but there seems to be some variability among sites here. SCAN sites may have measurements from more depths.
Soil moisture equation change - Feb, 2010
The NRCS issued a notice about a change in the equation used to convert sensor output to soil moisture in the winter of 2009/10. This will take effect for all data, including already collected data, beginning in February 2010. The change in the equation is documented in an article in the Vadose Zone Journal:
Seyfried, M.S., L.E. Grant, E.Du, and K Humes. 2005. Dielectric loss and calibration of the hydra probe soil water sensor. Vadose Zone J. 4:1070-1079
Data currently available on NRCS websites should be updated with this change.
See the sensor history page (linked on individual SNOTEL site pages) for detailed info on sensor maintenance, movement, or replacement.
- Louis Meadow site had sensors moved on 12/15/2003. Apparently sensors at -4 and -8 were moved to -8 and -20 respectively. Not sure if sensors were physically moved, or just renamed in the datalogger output.
- WVF is volume fraction of water in field moist soil (comparable to percent of field capacity)
- At least some files start or end with a few lines of data collected at odd intervals (bad data).
Data processing and filtering
For info on how the data were quality checked and filtered, see the data quality control page.
Some data was downloaded from the NRCS ftp site with help from Tim Bardsley, Dana Kuiper, and Maggie Dunklee.
Data from all SNOTEL sites with soil moisture and temperature profiles installed was obtained from the NRCS in the spring of 2009. This included data from 252 sites, including SCAN sites, for the period from install date to May 29, 2009. Data streams include soil moisture at up to 3 depths, soil temperature at up to 3 depths, avg air temp, max air temp, min air temp, snow depth, and snow water equivalent (SWE). Data were received as .csv files, one for each data stream at each site, with these fields and formats:
\^ Station ID \^ Date sampled \^ Variable code \^ Value \^ Quality control flag \^ | 3-4 digit int | yyyy-mmm-dd hh:mm:ss | String | Float | Character | | 345 | 2003-Sep-06 21:00:00 | WTEQ | -0.3 | V | | 345 | 2003-Sep-06 22:00:00 | WTEQ | -0.3 | V | | 345 | 2003-Sep-06 23:00:00 | WTEQ | -0.2 | E |
Soil moisture and soil temperature files do not have a QC control column. The station ID's are indexed along with their name, state, elevations, lat/lon, install dates, and other info in the soil_stations.csv file.