Description: 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.

Description: The data contain time series of optical-equivalent snow grain size (r_opt) retrieved from airborne spectral surface albedo measurements North of Greenland during PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project) in spring 2018. The data of three flights were measured under cloudless, low Sun, and partly rough surface conditions. Snow r_opt was retrieved from two wavelength approaches based on spectral surface albedo data using (i) the albedo ratio between 1280 nm and 1100 nm wavelength (ratio-method), and (ii) the surface albedo at 1700 nm (1700nm-method). The corresponding spectral surface albedo (also included in the data set) was derived from measurements by the Spectral Modular Airborne Radiation measurement sysTem (SMART) mounted on the Polar 5 research aircraft operated by AWI.

Description: Longwave and shortwave cloud radiative forcing derived from broadband irradiance observations (https://doi.org/10.1594/PANGAEA.900442) during the ACLOUD (Arctic CLoud Observations Using airborne measurements during polar Day) campaign in May / June 2017. This dataset contains only low-level flight sections (in case of clouds always below clouds). In addition, a cloud liquid water path equivalent derived from the shortwave transmissivity is given and a cloud-free albedo estimate during cloudy observations.

Description: During the ACLOUD (Arctic CLoud Observations Using airborne measurements during polar Day ) campaign in May / June 2017 spectral up- and downward irradiances were measured over the Arctic sea ice using the Spectral Modular Airborne Radiation measurement sysTem (SMART-Albedometer). The data set gives time series of irradiances measured along the flight path for three different wavelengths (555 nm, 645 nm, and 1640 nm) on different days and for different illumination conditions. The surface albedo can be directly calculated from the up- and downward irradiances. From these data set a temporal change of the sea ice albedo and a dependence on the illumination condition can be observed.

Description: Hyperspectral fields of visible and near infrared cloud top radiance observed by AISA Eagle (1024 spatial pixels and 504 spectral channels between 400 and 993 nm) and AISA Hawk (384 spatial pixels and 384 spectral channels between 931 and 2545 nm) during the ACLOUD (Arctic Cloud Observations Using airborne measurements during polar Day) campaign in May/June 2017.

Description: During the ACLOUD (Arctic CLoud Observations Using airborne measurements during polar Day) campaign conducted in May / June 2017, downward-looking commercial digital cameras equipped with a 180° - fisheye lens were installed on the aircraft Polar 5 and Polar 6. The images were used to derive the surface type fractions of snow/white ice, bare ice, melt ponds, and open water. The data set provides collocated broadband surface albedo, nadir brightness temperature, and surface type fractions along selected flight tracks of 21 flights.

Description: During the ACLOUD (Arctic CLoud Observations Using airborne measurements during polar Day) campaign conducted in May / June 2017, downward-looking commercial digital cameras equipped with a 180° - fisheye lens were installed on the aircraft Polar 5 and Polar 6. The images were used to derive the surface type fractions of snow/white ice, bare ice, melt ponds, and open water. The data set provides collocated broadband surface albedo, nadir brightness temperature, and surface type fractions along selected flight tracks of 21 flights.

Description: During the AFLUX (Airborne measurements of radiative and turbulent FLUXes of energy and momentum in the Arctic boundary layer) campaign conducted in spring 2019, a downward-looking commercial digital cameras equipped with a 180° - fisheye lens was installed on the aircraft Polar 5. The images were used to derive the surface type fractions of snow/white ice, bare ice, melt ponds, and open water. The data set provides collocated broadband surface albedo, nadir brightness temperature, and surface type fractions along selected flight tracks of six flights.

Description: During the PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project) campaign conducted in spring 2018, a downward-looking commercial digital camera equipped with a 180° - fisheye lens was installed on the aircraft Polar 5. The images were used to derive the surface type fractions of snow/white ice, bare ice, melt ponds, and open water. The data set provides collocated broadband surface albedo, nadir brightness temperature, and surface type fractions along selected flight tracks of seven flights.

Description: During the MOSAiC-ACA (MOSAiC-ACA (Multidisciplinary drifting Observatory for the Study of Arctic Climate - Airborne observations in the Central Arctic) campaign conducted in September 2020, a downward-looking commercial digital cameras equipped with a 180° - fisheye lens and a wide-angle camera system were installed on the aircraft Polar 5 and Polar 6. The images were used to derive the surface type fractions of snow/white ice, bare ice, melt ponds, and open water. The data set provides collocated broadband surface albedo, nadir brightness temperature, and surface type fractions along selected flight tracks of five flights.