Synoptic Categorization of Landfalling Atmospheric Rivers Near Dronning Maud Land, Antarctica Using Self-Organizing Maps

Atmospheric rivers (ARs) that reach the Antarctic Ice Sheet (AIS) transport anomalous moisture from lower latitudes and can impact the AIS via extreme precipitation and increased downward longwave radiation. ARs contribute significantly to the interannual variability of precipitation over the AIS and thus are likely to play a key role in understanding future changes in the surface mass balance of the AIS. While ARs impact the entire coastal AIS, coastal Dronning Maud Land (DML) is one of four East Antarctic maxima in AR frequency. Along with the high frequency of ARs, the variability of large-scale flow patterns associated with ARs around DML motivates further investigation of synoptic regimes favoring ARs in this region. This study utilizes self-organizing maps (SOMs) to identify synoptic-scale regimes associated with landfalling ARs in and near DML. The catalogue of ARs used in this research is output from a detection algorithm developed specifically for Antarctic ARs, and AR landfalls are identified at timesteps in which an AR overlaps with the AIS between 30°W and 30°E. To determine synoptic regimes conducive to AR landfall, sea level pressure anomalies between 60°W and 60°E from MERRA-2 at the time of AR landfalls are used to train a series of SOMs. Subsequent analysis of these SOMs will provide insight into: (1) the synoptic regimes that favor AR landfall near DML, (2) the preferred evolution of synoptic regimes during AR landfall over the DML, and (3), the extent to which AR properties and impacts vary as a function of the synoptic regime or evolution. The results from this analysis are expected to provide important context for understanding future impacts of ARs in DML.