Inter-annual and inter-decadal variability of the spring storm track over the North Pacific and its association with SST anomalies

Based on the 20CR reanalysis data and sea surface temperature (SST) data provided by European Center, the inter-annual (inter-decadal) variability of spring storm track over the North Pacific as well as the inter-decadal change in the relationship between the storm track and North Pacific SST are investigated. Results of Empirical Orthogonal Function (EOF) analysis show that there are two main variation modes for the spring storm track. The first mode represents its intensity variation and the second mode reflects its meridional variation in position. On the inter-decadal time scale, the relationship between the storm track and North Pacific SST anomalies mainly indicates an atmosphere-to-ocean forcing. Under different decadal backgrounds, 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 the storm track and North Pacific SST indicates an atmosphere-to-ocean forcing. Before 1977, however, the relationship reflected an ocean-to-atmosphere forcing that is opposite to the situation after 1977. Specifically, SST anomalies over the Kuroshio Extension imposed strong concurrent forcing on the atmosphere in the 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 behaves to lead the central North Pacific SST anomalies. However, before 1977, the meridional position of the storm track was also closely related to simultaneous SST anomalies in the equatorial eastern Pacific in the spring, implying ENSO's effect on the position of the storm track.