Developing an Objective Method to Measure Snow Depth
Snow Depth: Caleb Buchler – University of Delaware, Meteorology
Observer Guide: Ian Bailey
Mentor: Eric Kelsey, PhD Mount Washington Observatory/ Plymouth State University
The strong winds the summit experiences on a near-daily basis throughout the 8-month snow season drifts and scours the snow across the summit in a complex pattern that is challenging to average no matter the method. For over 85 years, MWO Observers have visually estimated snow depth at the summit of Mount Washington. A visual estimate of average snow depth inherently comes with significant subjectivity and uncertainty. An objective measure of snow depth is needed to meet National Weather Service and World Meteorological Organization guidelines.
The purpose of this project is to develop an objective method for measuring snow depth at the summit. The method developed must be subjective, be close to the true average snow depth, and also be logistically simple and robust enough that an Observer can take the measurement in extreme winds, frigid temperatures, and near-zero visibility in a short amount of time so that they can complete the other weather observations in time to submit to the National Weather Service.
Caleb Buchler continued the work done by previous intern, Chloe Boehm, in which she developed a snow depth measurement method that meets these requirements. Chloe’s method involves taking multiple measurements across the area where Observers make their visual estimate (the area between the precipitation can and the Sherman Adams Building), calculating an average snow depth, and then using statistics to determine the one point that is best representative of the average. Caleb, and the intern on the other shift Eve Cinquino, developed a dataset during the winter of 2019-2020 by measuring snow depth with a gradated avalanche probe at the nine points.
Together, Caleb and Eve measured snow depth at the same time that the Observers visually estimated snow depth 60 times. They recorded the snow depth for each of the nine points and calculated the mean for each measurement time. Using data from the 60 measurement times, Caleb did a statistical analysis to determine which site is most representative of the average. Caleb determined the one site that was closest to the overall average, had the lowest variance from the overall average, and was closest to the average most frequently. Caleb also discovered that the average snow depth was lower in the measured area than the visually-estimated average.
For future research, Caleb proposed putting stakes with measurement ticks in the ground at the nine locations before the winter season begins. This would reduce human error with measurements in the exact same location each time, allow the person measuring to go outside in high winds without having to carry an instrument, and allow for measurements that include ice layers that are difficult to penetrate and often form throughout the season.
Caleb taking measurements on a calm day. This was taken just south of the Sherman Adams Summit Building. For reference, the precipitation can is visible to his left while he is facing in the direction of the summit sign.