A decadal abruption of midwinter storm tracks over North Pacific from 1951 to 2010

Based on 60-year (1951-2010) reanalysis data of the National Oceanic and Atmospheric Administration and extended reconstructed sea surface temperatures, a detailed investigation was conducted to explore the midwinter storm track changes over the North Pacific. The root-mean-square (rms) of subweekly (2.5-6 days) transient of 300 hPa geopotential height field was calculated to represent the storm track. A decadal abruption occurred in 1982/1983, according to the Mann-Kendall test result. The first two Empirical Orthogonal Function (EOF) spatial patterns of the North Pacific storm track during P1 (1955-1982) and P2 (1983-2010) revealed opposite results: The EOF1 during P1 and the EOF2 during P2 revealed changes of intensity of the midwinter storm track in the North Pacific, whereas the EOF2 during P1 and the EOF1 during P2 exhibited a southward/northward shift of its central axis. In addition, pronounced differences in the thermal influence of the ocean on the storm track during P1 and P2 existed. A strong and sustained ENSO signal contributed to a storm track variation through the westerly jet from 1955 to 1982, as the storm track was observed to strengthen and shift equatorward during El Nino events. From 1983 to 2010, an apparent sea temperature frontal zone at approximately 40 degrees N and the associated near-surface baroclinicity resulted in the organization of a prominent mid-latitude storm track throughout the depth of the troposphere.