The relationship between the North Pacific midlatitude oceanic frontal intensity and the storm track and its future changes

The midlatitude oceanic front is a zonally elongated domain with a prominent sea surface temperature meridional gradient, which is a key region for the midlatitude air-sea interaction. The synoptic-scale transient eddy activity is prevalent over the midlatitude oceanic front, referred to as storm track, which plays an important role in the midlatitude weather and climate system. Therefore, it is of great significance to investigate the interaction between the midlatitude oceanic front and the storm track , which may help to understand and improve the theory of midlatitude air-sea interaction.

In this study, the relationship between the North Pacific midlatitude oceanic frontal intensity and the storm track is investigated based on the high-resolution oceanic and atmospheric reanalysis datasets. It is found that there exists a close association between the North Pacific storm track and the midlatitude oceanic front. The storm track strengthens (weakens) with the increased (decreased) oceanic front. The impact of the oceanic frontal intensity on the storm track is strongest in winter and spring, followed by autumn, and it is weakest in summer. The seasonal variations of the relationship between the two may be attributed to the near surface baroclinicity and the baroclinic energy conversion anomalies.

Additionally, future changes in the relationship between the North Pacific midlatitude oceanic frontal intensity and the wintertime storm track are projected based on a CMIP6 high-resolution climate model CNRM-CM6-1-HR. By comparing the relationship between the oceanic frontal intensity and the storm track under four different shared socioeconomic pathways (SSPs) with the historical run, it is found that there tends to exist the significant positive correlation under global warming, while the correlation will weaken in the storm track climatology and northern region, with the largest reduction in the high radiation scenarios (SSP5-8.5) and the least reduction in the medium to high radiation scenarios (SSP3-7.0). Further analysis indicates that the positive correlation between the oceanic frontal intensity and the near-surface baroclinicity also exhibits a similar weakened trend, which suggests that the projected changes in the relationship between the oceanic front and the storm track are mainly determined by the future changes in the relationship between the oceanic front and the near-surface baroclinicity.