Observing and modelling the effects of surface roughness on the albedo of Antarctic snow

Antarctica plays a crucial role in Earth's radiative energy balance, with the surface albedo of its snow cover being a key parameter.Snow albedo depends strongly on the optical properties of snow grains in the nearsurface layers.Other factors including illumination geometry, cloud conditions, and impurities influence albedo, though Antarctic snow is generally pristine.Surface roughness, operating at multiple scales, also modulates albedo and directional reflectance, but remains challenging to quantify.Advances in laser scanning have enabled high-resolution measurements over larger areas, opening new possibilities for modelling.While roughness-albedo relationships have been explored in alpine and boreal snow, Antarctic snow has not received equivalent attention.We conducted a field campaign in western Queen Maud Land during the 2022-23 austral summer, using Unmanned Aerial Vehicle (UAV)-mounted laser scanning alongside in situ observations to investigate the impact of centimeter-scale surface roughness on snow albedo.We observed surface roughness with mean root-mean-square (RMS) slopes in the range of 0.2 to 0.4 radians from the UAV, confirmed with near-surface laser scanning once scale variability was accounted for.The resulting albedo impact was in the range of 0.01 -0.06 (mean of ~0.03), in accordance with prior studies and exhibiting logical relationships with e.g.local snowfall or high wind events.