Variations Of The Spring Storm Track Over The North Pacific And North Atlantic And Their Associations With SST Anomalies

Based on the 20CR reanalysis data and sea surface temperature data provided by European Center, the variability of spring storm track over the North Pacific and North Atlantic as well as the relationships between storm track and SST anomalies on different time scales are investigated.Results show that there are two main variation modes for spring storm track over the North Pacific based on EOF analysis, i.e., the first mode as its intensity variation and the second mode as its variation of meridional position. On inter-decadal time scales, the relationship between storm track and North Pacific SST anomalies mainly indicates an atmosphere-to-ocean forcing. Under different decadal background, the inter-annual relationship between the storm track and SST anomalies over the Pacific Ocean exhibits different inter-decadal changes. After 1977, the relationship between the intensity of storm track and North Pacific SST indicates an atmosphere-to-ocean forcing, however, before that, their relationship reverses, indicating an ocean-to-atmosphere forcing, with SST anomalies over the Kuroshio Extension acting to force the atmosphere in the simultaneous spring. On the other hand, the relationship between the meridional position of the storm track and North Pacific SST anomalies after 1977 indicates an atmosphere-to-ocean forcing as the storm track acts to lead the central North Pacific SST anomalies,however, before 1977, the meridional position of storm track is also closely related to the SST anomalies in the eastern equatorial Pacific in the simultaneous spring,implying ENSO's effect on the position of storm track.Similarly, there are also two main variation modes for spring storm track over the North Atlantic based on EOF analysis. Its intensity and meridional position show significant inter-annual variation characteristics with 4 years of relatively stable period. On inter-annual time scales, the relationship between storm track and SST anomalies indicates the common role of oceans and atmosphere. The intensity of storm track acts to lead the tropical Atlantic SST anomalies, but is forced by the eastern equatorial Pacific SST anomalies in the previous winter. On the other hand,the position of storm tack acts to lead the SST anomalies east of Newfoundland, but is also forced by the SST anomalies in the eastern equatorial Pacific in the previous winter and simultaneous spring.The relationship between the position of spring storm track over North Pacific and North Atlantic exhibits inter-decadal changes. After 1960, the relationship reverses to anti-correlation in the form of a seesaw-like oscillation, maybe due to the increasing variability of SST which inspires more significant atmospheric circulation anomalies. Therefore, the anti-correlation coupling relationship between the position of spring storm track over North Pacific and North Atlantic is reinforced.