UAV Oblique Imagery Reveals Order-of-Magnitude Changes in Snow Aerodynamic Roughness Length Under Shifting Meteorological Regimes at Qinling Station, East Antarctica

Abstract

Snow aerodynamic roughness length ($z_0$) plays a critical role in Antarctic surface energy and mass balance. Yet, $z_0$ is conventionally treated as a constant in turbulent flux calculations. Fine-scale spatiotemporal variations in $z_0$ remain largely unmonitored. This study employed multi-temporal uncrewed aerial vehicle oblique photogrammetry to construct digital surface models and estimate $z_0$ values for various underlying surfaces and weather conditions with the bulk-aerodynamic method at Qinling Station, East Antarctica. The results demonstrate similar spatial distribution patterns among five $z_0$ estimation models, yet reveal an order-of-magnitude discrepancy in absolute values. The $z_0$ values in snow sastrugi areas are approximately an order of magnitude lower than those in rock areas. Snow surface $z_0$ shows high sensitivity to changes in meteorological conditions. Snowfall results in an increase of the regional mean $z_0$ in the snow sastrugi area from 0.01 to 0.10 mm, while strong winds reduce it by approximately one order of magnitude. Furthermore, $z_0$ tends to increase with the spatial sampling scales. Fine-scale estimation of $z_0$ can be combined with wind-based $z_0$ observations to provide a basis for developing high-fidelity snow-atmosphere interaction models, which is particularly crucial for simulating complex polar climates and environments.