Global Attribution of Precipitation to Weather Features

Abstract

Weather features, such as extratropical cyclones (ETCs), atmospheric rivers (ARs), and fronts, contribute to substantial amounts of precipitation globally. However, previous estimates of how much these individual features contribute to precipitation are very sensitive to subjectively chosen metrics. Furthermore, there is no information on how these weather features contribute to precipitation poleward of 60° latitude. To alleviate these shortcomings, we introduce a more robust attribution method applicable at all latitudes. Based on ERA5, we present the first global climatology of the contributions from cyclones, fronts, moisture transport axes (MTAs; AR-like features), and cold air outbreaks, as well as their combinations, to summer and winter precipitation as well as extreme precipitation. Most of the precipitation in the midlatitudes relates to the combination of ETC, fronts, and MTAs (28%), while in polar regions most precipitation occurs within the ETC-only category (27%). Extreme precipitation events in all extratropical regions are predominantly associated with the combination of ETCs, fronts, and MTAs (46%). In the midlatitudes, the combination of ETCs, fronts, and MTAs occurs almost 4 times as often during extreme events compared to regular events.