Insights into Cold Cloud Microphysical Processes Using Radar Doppler Spectra

Unraveling the complexities of cold cloud and precipitation processes is one of the leading challenges facing our community. The features captured by zenith pointing cloud radar Doppler spectra offer a particularly promising, information-rich window into these processes. For more than ten years, the United States Department of Energy ARM program has continuously recorded radar Doppler spectra at Barrow, on the North Slope of Alaska, creating a dataset now on the order of 100 million profile samples. Here we show that with such a vast dataset, microphysical processes can be targeted with exceptional specificity by imposing strict constraints on a number of parameters simultaneously, while still maintaining robust statistics. In contrast to the use of a case study approach, we instead apply techniques for compositing radar Doppler spectra across the entire data record, subject to tight controls over temperature and relative humidity through time coordination with balloon sounding launches. This framework gives us the ability to test various theories regarding the formation and growth of different ice particle forms with respect to temperature and liquid/ice supersaturation. Here we demonstrate evidence of secondary ice generation and growth through the Hallett-Mossop process and the production of small plates in the dendritic growth regime. In addition, we provide frequency of occurrence of the environmental conditions favorable to these processes, as well as that of supercooled liquid resolved in the vertical column.