Snow Specific Surface Area: Margins of Error, Best Methods, and Interpretation of In-Situ Measurements Using the IceCube, an Integrating Sphere

Snow specific surface area (SSA) is a minute physical property of snow that partially governs reflectance and plays an important role in microwave emission modeling and estimations of Earth's energy budget. SSA, or optical grain size, is an essential measurement for snow water equivalent (SWE) retrieval from radar but there are many challenges to acquiring in situ measurements. This project utilizes the IceCube, which measures snow SSA optically in the field. The IceCube is highly desirable for its ability to make in field measurements, although there are some uncertainties about its margin of error. Some studies that have used the IceCube have noted a difference between IceCube SSA and micro-CT SSA up to 25% and even higher in some cases. Data from the SnowEx campaign in March 2020, for example, shows that IceCube measurements are much higher than micro-CT measurements. This project took SSA samples using both IceCube and micro-CT from a wide variety of snow packs. Results are currently being analyzed with the goal of laying out sources of error, identifying trends in the SSA differences, giving a better margin of error for the IceCube, and prescribing the best methods for sampling with the IceCube. We hope that this will be useful to those who are not experts in microstructure but need accurate SSA measurements to validate modeling products, remote sensing data, as well as for other areas of study.