Extratropical cyclone energetics modulated by ocean meanders

Extratropical cyclones primarily develop over the western parts of ocean basins, where strong sea surface temperature (SST) contrasts form along western boundary currents such as the Gulf Stream in the Atlantic. These ocean currents are known to intensify extratropical cyclones by supplying moisture to the atmosphere through surface evaporation, which contributes to the diabatic heating associated with cloud formation and precipitation. While previous studies have highlighted the influence of the mean SST and SST gradient on cyclones developing over these currents, they have generally disregarded their meandering nature. Using idealized simulations, we examine the sensitivity of cyclone development to SST meanders of varying size through an analysis of the energy budget. In particular, we show that the moisture supply provided by warm SST anomalies associated with ocean meanders triggers diabatic heating a few hours later within storms. Both the size and phase of meanders relative to the cyclone modulate this energetic response. Such results reveal that not only the SST gradient but also the SST front geometry affect the life cycle of extratropical cyclones. Overall, our analysis provides insights into mechanisms of ocean-atmosphere interaction at the synoptic scale that, integrated over time, may have a noticeable impact on storm tracks at the climatological scale.

 

Reference: Vivant, F., Lapeyre, G. Meandering ocean currents modulate mid-latitude storm energetics (under review). https://doi.org/10.22541/essoar.175696970.05317808/v1.