Thursday, 29 June 2017
Salon A-E (Marriott Portland Downtown Waterfront)
We investigate the seasonal cycle of the Atlantic storm track and the occurrence of a midwinter minimum of eddy activity over the North Atlantic. Observations show that eddy kinetic energy over the Atlantic is reduced during winter relative to fall and spring, despite the stronger jet stream and enhanced baroclinicity, similarly to the well-known Pacific midwinter minimum. The reduction over the Atlantic is smaller and persists for a shorter period, yet it is statistically significant. To explore the potential role of the jet stream in driving this seasonal cycle, we present an analysis of years of strongest jet versus years of weakest jet over the Atlantic and Pacific basins. We find that when the wintertime jet is stronger, the midwinter suppression of eddy activity is more pronounced, as was found in observations of the Pacific storm track. We also explore the impact of the jet position on the Atlantic storm track seasonal cycle and the response to ENSO and NAO, and show the connection of the midwinter minimum to these modes of variability.
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