Synoptic Weather Types for the Ross Sea Region, Antarctica

ynoptic classifications over the Southern Ocean in the Ross Sea region of Antarctica (50°S–Antarctic coast, 150°E–90°W) have been derived from NCEP reanalysis data (1979–2011), producing a set of six synoptic types for the region. These types describe realistic synoptic conditions for the region and represent the moisture-bearing low pressure systems that circulate around Antarctica. The types are described as follows: low Bellingshausen/Amundsen (L-BA), low (L), zonal (Z), low Ross (L-R), ridge (R), and low Amundsen (L-A).Seasonal frequencies of the synoptic types reflect the seasonal zonal shift of the Amundsen Sea low (ASL) and also correlate well with the Southern Oscillation index (SOI) and the southern annular mode (SAM). Variability in the occurrences of the synoptic types L-R and L-BA indicate a shifting of the position of the ASL farther east (west) toward (away from) the Antarctic Peninsula during La Nina (El Nino) and positive (negative) SAM conditions. A joint linear regression of the...