The climatological mean enhancement of the turbulent air–sea heat exchange along mid-latitude sea surface temperature (SST) fronts highlights their crucial role for the atmospheric water cycle and storm tracks through the intensification of atmospheric cyclones and their associated precipitation. As part of a Norway–Japan collaborative project, we investigate the sensitivity of the atmospheric circulation – from synoptic to global scales – to SST fronts using a series of aqua-planet experiments. These experiments systematically vary the latitude and strength of the SST front to assess the relative importance of the structure of the SST front versus the SST itself. This presentation focuses on the atmospheric water cycle and storm-track activity. Varying the latitude of a zonally symmetric SST front, the mid-latitude atmospheric water cycle responds through distinct changes in surface latent heat fluxes, precipitation, and atmospheric moisture fluxes, whereas the tropical latitudes remain largely unaffected. As storm tracks are self-maintained through the diabatic generation of eddy available potential energy, the position of the storm track is diabatically anchored at the SST front. While the position of the SST front determines the position of the eddy moisture convergence and thus the diabatic heating that energizes the storm track, the underlying SST itself determines the general strength of the water cycle and thus the intensity of the storm track. Our results emphasize the fundamental role of SST fronts in organizing storm-track activity and the atmospheric water cycle. At the same time, the results highlight that smoothing the sharpness of the SST front while maintaining the cross-frontal SST difference does not significantly alter the atmospheric water budget or storm-track behavior, which is mainly driven by the overall difference in SST across the SST front. The strong connection between the eddy moisture flux and the SST front provides a diabatic pathway to anchor storm tracks along SST fronts.

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