Hemispherical-directional reflectance factor (HDRF) of snow surfaces retrieved from airborne camera measurements in Antarctica during austral summer in 2013/14

• Main Authors: Carlsen, Tim, Birnbaum, Gerit, Ehrlich, André, Helm, Veit, Jäkel, Evelyn, Schäfer, Michael, Wendisch, Manfred
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 2020
• Subjects: anisotropy; BRDF; camera observations; HDRF; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; reflectance; remote sensing; snow; snow grain size; snow surface roughness; SPP1158; albedo; Alfred Wegener Institute; Antarc*; Antarctic; Antarctica; Sea ice; The Cryosphere
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.921707; https://doi.org/10.1594/PANGAEA.921707

The hemispherical-directional reflectance factor (HDRF) of snow surfaces was measured in Antarctica during austral summer in 2013/14. The HDRF was retrieved from airborne measurements using a digital 180° fish-eye camera onboard the research aircraft Polar 6 operated by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Bremerhaven, Germany. -- The dataset contains the weighting functions for isotropic (f_iso), volumetric (f_vol), and geometric (f_geo) scattering obtained by inverting the kernel-driven, semi-empirical Ross-Thick-Li-Sparse-Reciprocal model for the bidirectional reflectance distribution function (BRDF). Along with the weighting functions f_iso, f_vol, and f_geo, the weights of determination (WoD) and root-mean-square errors (RMSE) are given as a criterion for the quality of the inversion for all 3 camera channels (Red: 602 nm central wavelength, Green: 538 nm, Blue: 470 nm). In addition, the footprint size of the camera observations is stated. -- The snow HDRF was measured over a variety of different solar zenith angles, optical-equivalent snow grain sizes, and surface roughness, which are given as parameters within the dataset. The optical-equivalent snow grain size was retrieved from spectral surface albedo measurements with the Spectral Modular Airborne Radiation measurement sysTem (SMART) mounted on Polar 6 using observations at 1280 and 1100 nm wavelength. The surface roughness was measured using the airborne laser scanner RIEGL VQ580 on Polar 6. -- Averaging was performed over time intervals of 30 s. The number of camera pictures, SSA measurements and laser scanner observations used for averaging over each 30s-interval are given. -- The dataset further includes basic flight parameters such as the second of day, longitude, latitude, flight altitude, surface elevation, aircraft velocity, and an attitude flag (0 = okay, 1 = do not use) corresponding to the times of measurement. -- Use of these data requires prior OK from the PIs.