Data Description

Data Description

Daily data is collected at 25 sites throughout New Hampshire. At each site data is collected at local solar noon (+/- 30 minutes) by the observer. Data collection procedures are as follows:

  • Surface Albedo: The observer picks a location of undisturbed snowpack in an open area (e.g., no shade from trees or buildings) at local solar noon and records the start time of the observation. The observer points the leveling boom at the sun and uses the circular levels to level the pyranometer optic facing upward.  The observer records the incoming solar radiation in W/m2 and then rotates the leveling boom 180° so that the pyranometer optic faces downward at the ground. The observer levels the boom and records reflected solar radiation in W/m2. The observer then repeats upward and downward paired measurements three times and records the end time of the observation. Albedo is calculated as the sum of the three reflected measurements divided by the sum of the three incoming measurements.
  • Snow Depth: The observer inserts an aluminum snow tube vertically into the snow pack and records snow depth using 0.5” increments marked on the outside of the tube and prepares the snow sample collection for snow density measurement.
  • Snow Density: The observer caps the top end of the snow tube and uses a metal scraper to expose the length of the tube to the grass or soil surface. The metal scraper is gently slid under the snow bottom of the snow tube, lifted out of the snowpack, and rotated until the tube is horizontal. The observer inspects the bottom of snow tube and removes any vegetation, soil, or rocks from the tube. The bottom cap is placed on the snow tube and weighed using the digital hanging scale. Total weight of snow tube and snow sample are recorded and entered in the online database. Within the database, snow density is calculated as the mass of the snow sample (total weight minus empty tube + caps, in pounds) divided by the volume of the snow sample (snow depth * pi * [inner diameter of tube/2]2). Snow density values are converted to kg/m3 by the data entry system.
  • Surface Temperature: The observer points the IR temperature gun vertically 3” above the snow or ground surface and records the value (°F) on the digital readout after 10 seconds.
  • Cloud Cover: The observer notes cloud cover as all clear (0% cloud cover, ACLR), clear (1%-30% cloud cover, CLR), partly cloudy (30-60% cloud cover, PCL), or overcast (60-100% cloud cover, OVC).
  • Additional Comments: 

    The Observer Notes:

    • Whether vegetation is visible beneath snow pack
    • Presence of debris on top of the snow pack
    • Location of clouds during albedo measurement (e.g., measurement made while the sun was behind a cloud)
    • Snow texture (fine-grained, coarse-grained, icy)
    • Snowfall within the last 24 hours
    • Melt within the last 24 hours
    • Snowing at the time of measurement

The data processing/quality control procedure is conducted when the observer enters the data into the data entry form. The NH EPSCoR-funded infrastructure of web servers and the availability of custom implemented and publicly available/open-source tools are used to process and visualize the data once entered into the database. The observers are requested to re-enter values if the following errors occur:

  • Albedo values greater than 1.0 are rejected. The observers are asked to check that incoming and reflected measurements were entered into the correct boxes.
  • Snow Density values greater than 1000 kg/m3 are rejected. The observers are asked to check that their snow depth measurements were entered in inches and that the weight was measured in pounds.