2020 Volume 98 Issue 3 Pages 527-550
Data from the continuous observations of four shallow snow events (echo top < 8 km) and two deep events (> 10 km) were obtained using the C-band vertically pointing radar with frequency-modulation continuous-wave technology with extremely high resolution during the winter of 2015–2016 in middle latitudes of China. Snow-generating cells (GCs) were found near the cloud top in each event. Reflectivity (Z), radial velocity (Vr), and the vertical gradients of Z (dZ/dh, where h is the vertical distance) and Vr (dVr/dh) showed different vertical distribution characteristics between the upper GC and lower stratiform regions (St regions). Fall streaks (FSs) associated with GCs were embedded in the St regions. In the deep events, the proportions of GC regions were slightly larger, but the average contributions to the growth of Z (33 %) were lower than those in the shallow events (42 %). The average d Z /dh values were usually two to three times larger inside GCs and FSs compared to outside. Bimodal Doppler spectra were used to establish the relationships between Z and the reflectivity-weighted particle fall speed (Vz) for the two regions. The vertical air velocity (Wa) and Vz were then retrieved, and the results showed that both the updraft and the downdraft were alternately observed in GC regions. GC locations were usually accompanied by strong upward air motion, with average speeds mostly distributed around 1.2 m s−1, whereas downward air motion often appeared between GCs. In the St regions, the speeds of Wa were mainly within 0.5 m s−1. The upper areas of the St regions consisted primarily of weak upward motion, whereas weak downward motion dominated the lower areas. There was no apparent difference in Wa inside and outside the FSs. The average Vz was slightly larger inside GCs and FSs compared to outside, with a difference of 0.1–0.3 m s−1 and 0.2–0.4 m s−1, respectively.
