Radar Observations of Cold Air Outbreak Snowfall in East China: Variations of Z‐S Parameterizations and Microphysical Impacts

Abstract In this study, we characterized cold air outbreak (CAO) snowfall over the Shandong Peninsula, East China, using gauge and weather radar observations from 2020 to 2024. We developed a gauge‐radar matched data set and determined the coefficients in Z = aS b every 30 min using a differential evolution algorithm. The results show that the exponent b is relatively stable at 1.72 whereas the prefactor a shows large variations. Then, we fixed b at 1.72 and classified a values into three groups. Our analysis suggests that a larger prefactor a is characterized by smaller peak reflectivity, larger differential reflectivity, larger specific differential phase, larger mean volume diameter, smaller number concentration and smaller snowfall rates and vice versa. We present two cases with contrasting values of a (109.0 vs. 567.8). Surface disdrometer observations suggest that the first event is characterized by significant riming, whereas the latter exhibits signatures of unrimed snow aggregates. Further spectral analysis of the radar mosaic for the two events reveals wavelengths of 29.5 and 141.1 km, with corresponding periods of 0.6 and 3.1 hr, respectively. Multi‐event 2DFFT wavelength analyses suggest that the microphysics of CAO snowfall are associated with the spatial structure of the snowstorm system.