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

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.