Macro- and Microphysical Properties of Atmospheric River Snowfall: Results from Two Instrument Sites

Atmospheric rivers (ARs) can produce intense snowfall events with different characteristics compared to snowfall events not associated with ARs. This study uses remotely sensed and in situ observations at multi-year instrument sites in Marquette, Michigan and Hyytiälä, Finland to comprehensively evaluate snowfall properties during ARs and compare to snowfall properties during non-AR conditions (NoAR). A snowfall classification scheme is applied at each site to find deep (large-scale) snowfall events and classify them as either AR or NoAR snowfall. To identify differences between the two regimes, reanalysis data products and ground-based observations are utilized to examine the large-scale properties, environmental conditions, and macro- and microphysical characteristics of AR and NoAR snowfall. During AR snowfall, there is a preferential large-scale setup at both instrument sites that result in enhanced water vapor transport. The AR snowfall events produce higher snowfall rates, as well as a higher number of denser and faster falling snow particles compared to NoAR snowfall.