Drifting snow threshold measurements near McMurdo station, Antarctica: A sensor comparison study

We present the results of an Antarctic spring field study of snow drift threshold measurements made using two custom drift sensors and a commercial parts-counting device. All three sensor types worked well at detecting drifting snow events, but the sensors recorded different magnitudes (particle count per unit time) of drift. Each sensor has a unique detection threshold for particle size, and responded differently to identical wind and snow conditions, although the particle counts from the different sensors are linearly related at low wind speeds. The drift threshold is defined here as the minimum friction velocity at which drifting snow was observed during more than 10% of measurements at that wind speed. The results of this multi-sensor study demonstrate that the drift threshold is lower (friction velocity of 0.2 m/s) for very small particles that are likely transported in suspension than for coarse-grained saltating particles (0.25 m/s). These friction velocities correspond to 10-meter wind speeds of 5.6 and 7.2 m/s respectively for the conditions during this experiment. The commercially available parts counter is recommended as a low-cost alternative to custom-built drift sensors for use in future field studies of drifting and blowing snow.