What Are the Most Important Contributors to Arctic Precipitation—When, Where, and How?

ABSTRACT The Arctic climate system is experiencing large changes associated with global warming. Precipitation is a crucial factor linking the atmosphere with other climate compartments, for example, ocean and cryosphere. Using atmospheric reanalysis (ERA5) we assess the role of atmospheric weather systems, that is, atmospheric rivers, cyclones, and fronts. When: Averaged over the whole Arctic (> 70° N), a strong seasonal cycle exists with twice as much precipitation in summer than in winter when frozen precipitation is mainly brought by cyclones. In summer, the highest total precipitation amounts are rather equally contributed by all weather systems. Where: In winter, the Arctic North Atlantic region experiences by far the highest precipitation amounts, whereas in summer precipitation is more evenly distributed over the whole Arctic. How: Overall, cyclones are the most important contributor to precipitation. The highest precipitation intensity occurs when atmospheric rivers, cyclones, and fronts coincide, whereas the lowest precipitation rates occur when precipitation cannot be attributed to any of these weather systems. This residual makes up almost half of the annual snowfall, most of it in the central Arctic, and 25% of rainfall. Marine Cold Air Outbreaks can explain part of the residual. The amount and drivers for light “trace” precipitation requires further investigation.