Arctic observations and numerical simulations of surface wind effects on Multi-Angle Snowflake Camera measurements

Abstract. Ground-based measurements of frozen precipitation are heavily influenced by interactions surface winds with gauge-shield geometry. The Multi-Angle Snowflake Camera (MASC), which photographs hydrometeors in free-fall from three different angles while simultaneously measuring their fall speed, has been used the field at multiple midlatitude and polar locations both without wind shielding. Here, we present an analysis Arctic observations – a Belfort double Alter shield compare results to computational fluid dynamics (CFD) simulations airflow corresponding particle trajectories around unshielded MASC. MASC-measured speeds well Ka-band Atmospheric Radiation Measurement (ARM) Zenith Radar (KAZR) mean Doppler velocities only when light (≤5ms-1) MASC is shielded. that do not match KAZR-measured tend below threshold value increases approximately linearly speed but generally <0.5ms-1. For those events ≤1.5ms-1, orientation angle mode 12∘ horizontal plane, large, low-density aggregates as much 5 times more likely be observed. Simulations absence show separation flow upstream side instrument, upward velocity component just above aperture, decreases 55 % (74 %) for m s−1 (10 s−1). We conclude accurate microphysical, orientation, characteristics snow particles require shielding fence restriction where (≤5ms-1). Hydrometeors still air, so adjustments these properties' distributions within natural turbulence remain determined.