Physical Drivers of Thin Snowpack Spatial Structure from Unpiloted
Aerial System (UAS) Lidar Observations
Abstract
Snow distribution is a function of interactions among static variables,
such as terrain, vegetation, and soil properties, and dynamic
meteorological variables, such as wind speed and direction, solar
radiation, and soil moisture that occur over a range of spatial scales.
However, identifying the dominant physical drivers responsible for
spatial patterns of the snowpack, particularly for ephemeral, shallow
snowpacks, has been challenged due to the lack of the high-resolution
snowpack and physical variables with high vertical accuracy as well as
inherent limitations in traditional approaches. This study uses an
Unpiloted Aerial System (UAS) lidar-based snow depth and static
variables (1-m spatial resolution) to analyze field-scale spatial
structures of snow depth and apply the Maximum Entropy (MaxEnt)
framework to identify primary controls over open terrain and forests at
the Thompson Farm Research Observatory, New Hampshire, United States. We
found that, among nine topographic and soil variables, plant functional
type and terrain roughness contribute up to 80% and 76% of relative
importance in MaxEnt to predicting locations of deeper or shallower
snowpacks, respectively, across the landscape. Soil variables, such as
organic matter and saturated hydraulic conductivity, were also important
controls (up to 70% and 81%) on snow depth spatial variations for both
open and forested landscapes suggesting spatial variations in soil
variables under snow can control thermal transfer among soil, snowpack,
and surface-atmosphere. This work contributes to improving land surface
and snow models by informing parameterization of the sub-grid scale snow
depths, downscaling remotely sensed snow products, and understanding
field scale snow states.