Topographic Correction of Snow Albedo Measured from a UAV (Extended Abstract)

The albedo of seasonal snowpack exerts considerable control on the Earth’s energy balance and is highly variable throughout space and time. Accurate quantification of snow albedo can be achieved through physically-based modeling approaches that are initialized or updated by optical satellite observations. Near-surface measurements are critical for validating both modeled and satellite-based reconstructions of snow albedo. Uncrewed Aerial Vehicles (UAVs) equipped with upward and downward-facing pyranometers provide high-resolution measurements of broadband albedo, spatially distributed across landscapes at scales not attainable by current satellite technologies. UAV surveys can deploy across heterogeneous terrain to acquire representative measurements of a diverse range of snow-covered environments, providing an improved source of calibration and validation data over traditional point-based measurements. Since UAV measurements can be taken near the surface (10 m - 100 m), they greatly reduce atmospheric and geolocational error sources. Near-surface measurements are still susceptible to other sources of error that must be corrected for if measurements are to be used operationally. Variable terrain introduces error in albedo measurements as reflectance measurements are not representative of surface conditions when they are taken at an oblique angle to the surface, introducing the need for topographically corrected albedo measurements. The tilt of the UAV platform can also compound this error.