The Influence Of Atmospheric Rivers On Cold-Season Precipitation In The Upper Great Lakes Region

This study aims to identify the impacts of atmospheric rivers (AR) associated with cold-season precipitation in the Upper Great Lakes region of the United States. A MERRA-2-derived AR dataset is combined with data from a suite of instruments hosted by the National Weather Service in Marquette, Michigan, including a profiling radar and a video disdrometer. ARs coincide with deep, synoptically-forced precipitation 28% of the time during the cold season. These ARs are found to intrude from the southwest and are associated with warmer surface and upper-level temperatures, increased radar reflectivity values, and enhanced precipitation rates. Warmer atmospheric temperatures aloft associated with ARs lead to a fourfold increase in the likelihood that cold-season precipitation will be rain instead of snow. Additionally, inland ARs in the Upper Great Lakes region are correlated with the negative phases of the Pacific Decadal Oscillation and the Pacific-North American pattern.Plain Language Summary The Upper Great Lakes region of the United States experiences an abundance of snowfall each year. The National Weather Service in Marquette, Michigan closely monitors snowfall events due to the socioeconomic impact on the surrounding communities. Studies have shown that intrusions of enhanced levels of atmospheric water vapor, or "atmospheric rivers", lead to increased precipitation along oceanic coastlines and other parts of the interior United States. This study investigates the impact of atmospheric rivers on cold-season precipitation in the Upper Great Lakes region using ground-based observations from Marquette. We find that atmospheric rivers occur frequently during large-scale, deep precipitation events and are associated with enhanced precipitation rates, greater likelihood of rain instead of snow at the surface, and warmer temperatures. These events are also correlated with well-known climate variability patterns, which could aid forecasters in mid- and long-range prediction of these weather events.Key PointsDeep, synoptically forced cold-season precipitation is frequently associated with atmospheric rivers (ARs) in the Upper Great Lakes regionPrecipitation rates are enhanced and rain is four times more likely to occur than snow if an AR is proximalUpper Great Lakes ARs are significantly correlated to negative phases of the Pacific-North American pattern and Pacific Decadal Oscillation