The Modulation of Gulf Stream Influence on the Troposphere by the Eddy-Driven Jet
The main aim of this study is to better understand the relative roles of the large-scale ocean and atmosphere circulations in the ocean-to-atmosphere forcing near the Gulf Stream by exploring the observed relationship between the North Atlantic eddy-driven jet (EDJ), the Gulf Stream SST front, and atmospheric frontal variability in the context of how deep the Gulf Stream influence extends into the troposphere.
Since the ocean-to-atmosphere feedback near the Gulf Stream can be a source of predictability for the downstream extreme weather events, our result implies such predictability can be sensitivity to the EDJ latitude and particularly enhanced when the EDJ is in its southern regime.
This study suggests that the Gulf Stream influence on the wintertime North Atlantic troposphere is most pronounced when the EDJ is farthest south and better collocated with the Gulf Stream. Using the NCEP-CFSR reanalysis for December–February 1979–2009, the daily EDJ latitude is separated into three regimes (northern, central, and southern). It is found that the average trajectory of atmospheric fronts covaries with EDJ latitude. In the southern EDJ regime (~19% of the time), the frequency of near-surface atmospheric fronts that pass across the Gulf Stream is maximized. This significantly strengthens near-surface atmospheric frontal convergence resulting from strong air-sea sensible heat flux gradients. Thus the atmospheric fronts associated with a southern EDJ primarily sets the time mean convergence and vertical motion, due to enhanced Gulf Stream air-sea interaction.