Hadleigh D. Thompson, Julie M. Thériault, Nicolas R. Leroux (2022). A mixed-phase precipitation deployment of a Multi Angle Snowflake Camera . Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

Measuring solid precipitation phase and type at the surface is crucial for better understanding their formation mechanism and improving their representation in models. Such measurements are commonly taken manually and, when possible, with macrophotography. The Multi-Angle Camera (MASC) allows for automatic observations of solid precipitation type at the surface without an observer being present. The MASC has previously been deployed in regions such as the Colorado Rockies, the Swiss Alps, and Antarctica, yet not in a mixed phased precipitation orientated campaign. The Saint John River Experiment on Cold Season Storms (SAJESS) provided such an opportunity, with an intensive observation period (IOP) running March-April 2021 in Edmundston, New Brunswick. During this period, five storms with mixed-phase (both rain and snow) precipitation occurred. Here, we explore the potential for the MASC to contribute to mixed-phase precipitation observations by delineating between images of solid and liquid particles. After 980 hours of operation, a previously published supervised detection algorithm was used to process over 93,000 collected images, with the algorithm detecting solid particles 92% of the time during the mixed phased events. This contrasts with manual observations for the same period that recoded 50/50 rain and snow observations, implying that liquid particles may be seen as solid by the MASC. During snow events, however, when only solid particles were recorded during manual observations, MASC data compare favorably in both precipitation type and timing. Ongoing work includes further analysis of MASC data, including particle size and fall speed measured during rain-only events, with the aim of improving the detection algorithms' ability to identify liquid particles. This research highlights the current limitations, yet also the potential, of the MASC to identify mixed precipitation.

First Author: Hadleigh D. Thompson, Département des sciences de la Terre et de l’atmosphère, Université du Québec à Montréal
Additional Authors: Julie M. Thériault, Département des sciences de la Terre et de l’atmosphère, Université du Québec à Montréal; Nicolas R. Leroux, Département des sciences de la Terre et de l’atmosphère, Université du Québec à Montréal