Comparison of the Precipitation Structure and Microphysical Properties within Two Alberta Clipper Systems During the 2022 IMPACTS Deployment

Mid-latitude winter cyclones in North America exhibit wide variability in synoptic-scale forcing mechanisms, storm tracks, and moisture sources which impact the development and evolution of these systems. Alberta clipper-type storms are typically fast-moving, exhibit low moisture content, and traverse the plains states, upper Midwest, Northeast, and southern parts of Canada. Nonetheless, these systems can have strong frontogenetic forcing, produce localized regions of significant snowfall accumulation with a high snow-to-liquid ratio, and present challenges for operational forecasting. Since observations of the in-situ microphysics and physical structure from airborne radars within these storms are limited, information on the microphysical processes present in these storms is of interest to improve numerical models and remote sensing retrievals.

Two Alberta clippers were sampled in the Northeast US and Québec during the 2022 deployment of the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) experiment. IMPACTS is a five-year NASA-funded mission aimed at characterizing banded precipitation structures and understanding the dynamic, thermodynamic, and microphysical processes associated with enhanced precipitation using a satellite-simulating ER-2 and a storm-penetrating P-3 aircraft.

The two clippers exhibited different frontal forcing, instability, and moisture content that impacted the precipitation structures and microphysical properties. The clipper system with greater forcing and instability exhibited more prominent snowbands, higher variability in the cloud depth, larger aggregates, and greater vertical motions than the other storm. The stronger clipper also exhibited reflectivity that increased more rapidly with temperature, the mass-weighted mean diameter Dm was 37% larger, and ice water content was 14% lower compared to other snowstorms sampled during the 2020 and 2022 deployments. Ground-based measurements from radars, disdrometers, radiosondes, and surface stations put the observed snowfall rates in context with radar observations. Lastly, a pre-existing neural network radar retrieval is used to relate the multi-frequency radar measurements to microphysical properties within the Alberta clippers.