Measurements of drifting and blowing snow at Iqaluit, Nunavut, Canada during the star project

Abstract A 10 m meteorological tower near Iqaluit Airport was operational from late October 2007 to early April 2008. Measurements included wind speed, temperature, pressure, humidity, visibility, and blowing snow number flux. Number flux measurements give a frequency of blowing and drifting snow of approximately 10% for the duration of the study, while meteorological observations from the Iqaluit weather office give a frequency of approximately 5%. Winter winds were predominantly from the northwest, and some strong southeasterly winds were also observed, especially in early spring. The average roughness length determined from the variance of wind speed is z0 = 0.14 mm. Threshold wind speeds for the onset of blowing snow ranged from 7 m s–1 to 12 m s–1, excluding events with falling snow. Measurements of visibility correlate well with the measured number density (R2 = 0.83), assuming a constant particle diameter of d ≈ 100 μm at a height of 2 m. A camera system was used during blowing snow events in February to measure the size of blowing snow particles and the mass flux of blowing snow. At a height of 0.35 m, the particle size distribution can be approximated by a gamma distribution with shape parameter 4.4 < α < 6.4 and an average particle diameter of 70 < d < 148 μm. The particle size at a height of 0.35 m increases linearly with the 10 m wind speed (R2 = 0.69). Mass flux measurements demonstrate a power law relation with height between 0.1 and 0.9 m, with a negative exponent of approximately 2.5. Blowing snow density follows a power law relation with height between 0.85 and 1.85 m, with a negative exponent of approximately 1.3 for friction velocity 0.25 < u* < 0.55 m s–1. In February 2008, a field mill was installed, which measured electric field strengths as high as 26.2 kV m–1 at a height of 0.5 m.