A description of the Ross Ice Shelf air stream (RAS) through the use of self-organizing maps (SOMs)

The low-level wind field across the Ross Ice Shelf region, Antarctica is studied through the method of self-organizing maps (SOMs). Emphasis is placed on identifying and characterizing the Ross Ice Shelf air stream (RAS). The RAS is a dominant northward stream of air resulting in significant transport of atmospheric mass from the interior of Antarctica. Two SOMs are created for the lowest model level (similar to 13 m) and the 5th lowest model level (similar to 150 m), from archived real-time numerical weather prediction output of the Antarctic Mesoscale Prediction System (AMPS). A verification of the SOM for the lowest model level is completed by comparing select nodes to automatic weather station wind rose plots. The winds depicted in the lowest model level SOM are dominated by the position of the cyclone in the Ross Sea and the changes in wind speeds on the Antarctic plateau. The 5th lowest model level provides a better depiction of the RAS. The RAS is found to be present primarily when associated with a cyclone in the Ross Sea. There is a strong seasonality to the RAS with the RAS occurring frequently during the winter months and rarely during the summer months. The structure and position of the RAS is strongly dependent on the position of the Ross Sea cyclone.