Title --- SOS_SnowPits Authors --- Daniel Hogan Lead and corresponding author Graduate student 925-588-4507 Civil and Environmental Engineering University of Washington 201 More Hall, Box 352700 Seattle, WA 98195-2700 https://orcid.org/0009-0008-0553-6783 dlhogan@uw.edu Eli Schwat https://orcid.org/0000-0003-1212-5735 elilouis@uw.edu Civil and Environmental Engineering, University of Washington Jessica Lundquist https://orcid.org/0000-0003-2193-5633 jdlund@uw.edu Civil and Environmental Engineering, University of Washington Ethan Gutmann https://orcid.org/0000-0003-4077-3430 gutmann@ucar.edu National Center for Atmospheric Research: Boulder, CO Julie Vano jvano@agci.org Aspen Global Change Institute Dataset Description --- **Introduction** This dataset contains data and information acquired from manual snow pits following protocols and symbology from the International Classification for Snow on the Ground (see document attached titled IntClassificationSnowOnGround.pdf). Snow pits were dug approximately every 24 to 48 hours between January 6 and March 16, 2023. The main measurements taken from each snow pit included total snow depth, surface temperature, snow temperature (every 10 cm), snow density (10 cm average), snow crystal size, snow crystal type, and layer hardness. **Data version number and date** Version 1, 2023-11-27 **Data Status (Preliminary or Final)** Preliminary **Time period covered by the data** 2023-01-06 to 2023-03-16 **Physical location** Latitude/Longitude: 38.958330, -106.989055 Elevation: 2892 meters **Data Frequency** Approximately every 24 to 48 hours. Instrument Description --- Temperature was recorded using a Cooper Atkins-DFP450W Digital Pocket Thermometer. Surface temperature was also recorded using a infrared thermometer. Snow depth was evaulated using a foldable ruler. Snow density was measured using a 1000 cubic centimeter density cutter and digital balance with 1g resolution. Temperature and density data is also provided as a netcdf file (.nc). with two dimensions. *time* - the start time of each snow pit, in UTC time, format dd/mm/yyyy HH:MM:SS. *depth* - the depth of each layer of measurement. One coordinate is availalbe *id* - the id of the snow pit, following the convention KPxx, related to the time dimension. Five variables were recorded: *temperature [C]* - temperature of the snow pit layer. The initial value is the temperature of the surface taken using the digital thermometer. Values were collected every 10 cm down to the ground surface. The 0 depth measurement was as the snow-ground surface interface. *density [g/m3]* - density measured using the 1000 cc density cutter and digital scale. Measurements were collected every 10 centimeters down to the ground surface, so values are 10 cm layer average density. The PDF version of each snow pit contains specific information about the impacts from ground vegetation covered by the snow (e.g. bushes) which may have impacted the measurement of snow density. *ir_surface_temp [C]* - the surface temperature collected using the infrared thermometer. *thermometer_surface_temp [C]* - the surface temperature collected using the digital thermometer. *pit_total_snow_depth [cm]* - the total depth of the snow pit. Attributes for each measurement are available within the netcdf file. ​ Data Collection and Processing --- Snow pits were dug within a 20 by 50 meter area, 10 meters down-valley of the SOS deployment. To avoid impacts from the sun warming the snow pit face where measruments were taken, each snow pit was dug in the same south-southwest direction. Thus, the face of the snow pit where measurements were acquired was north-northeast facing. Each measurment location was in previously undisturved snow. Each new pit was located approximately 1 meter south-southwest of the previous pit location. Snow pits were dug down to the ground surface with the north and east facing walls carefully flattened and smoothed until approximately vertical. Once the snow pit was fully dug, surface temperature measurements near the snow pit openeing were recorded using the digital thermometer which was shielded from solar heating using a snow shovel. Surface temperature from the infrared thermometer was also recorded. The digital thermometer was again used to record the temperature within the snowpack at 10 centimeter intervals down to the ground surface. The final measurement made was at the interface of the snowpack and the ground surface. Once temperatures were recorded, layers within the snowpack were delineated using the hand hardness test, with softest conditions represented as "fist hardness" and hardest conditions represented as "ice hardness". A descripition of the hand hardness test is available in the IntClassificationSnowOnGround.pdf file. After layer hardness was determined, snow density was recorded at 10 centimeter intervals down to the surface using the density cutter and scale. To take a measurement, the density cutter handle was oriented vertically and the cutter was carefully inserted into the snowpack exactly perpindicular to the snow pit face and cut out using the accompanying scraper to extract a snow sample. A sample was retaken if the snow sample was determined to not fully fill the density cutter. The snow sample was then taken to the scale that had been tared to the weight of the empty density cutter. The weight of the sample was then recorded. Since the volume of the density cutter is 1000 cubic centimeters, values were recorded as kg/m3. Once density measurements had been taken, snow crystal form and median size within each hardness layer was evaluated and recorded. The snow pit was then refilled with the previously dug out snow and a flag was placed to mark the location of the snow pit face used for measurement so the next pit could be dug in a new location. All snow pit data was originally recorded in notebooks in the field and then recorded in SnowPilot, an online repository for snow pit visualization (https://snowpilot.org/). PDFs and XML files were downloaded from Snow Pilot. Temperature and density profiles were extracted from XML files and then converted to a netcdf format. Data Format --- Temperature and density profiles for each of the 48 snow pits are available in the KettlePondsSnowPits.nc file. PDFs for each of the 48 snow pits dug over the 2023 winter at the Kettle Ponds site are available in the KettlePondsSnowPits.pdf file. A PDF of the snow pit dug at Avery Picnic is available in the AveryPicnicSnowPit.pdf file. Data Remarks --- When selecting a specific snow pit within the netcdf file, ensure that nan values are dropped for the density or temperature measurements. Again the first (surface) temperature measurements are from the digital thermometer, but can be replaced with values from the IR thermometer, if desired. Data was collected on a semi-regular basis during the winter deployment, but specifically after snow storms or large wind events over the course of the 2023 winter season. An additional snow pit was dug at the upvalley Avery Picnic site (38.97187 N, -106.99653 W) on January 29. This pit data is located in the AveryPicnicSnowPit.pdf file. References --- The International classification for seasonal snow on the ground—UNESCO Digital Library. (n.d.). Retrieved February 15, 2023, from https://unesdoc.unesco.org/ark:/48223/pf0000186462 Appendix --- GCMD science keywords: EARTH SCIENCE>RYOSPHERESNOW/ICE>SNOW WATER EQUIVALENT EARTH SCIENCE>CRYOSPHERESNOW/ICE>SNOW DEPTH EARTH SCIENCE>CRYOSPHERESNOW/ICE>SNOW STRATIGRAPHY EARTH SCIENCE>RYOSPHERESNOW/ICE>SNOW/ICE TEMPERATURE EARTH SCIENCE>RYOSPHERESNOW/ICE>SNOW DENSITY