Lia Siegelman (Scripps Institution of Oceanography, USA); Patrice Klein (LMD-IPSL, JPL-Caltech, USA); Torres Hector (JPL-Caltech, USA); Dimitris Menemenlis (SJSU, JPL-Caltech, USA); Andrea Molod (NASA Goddard Space Flight Center, USA)

The dynamics of mid-latitude storms are driven by moisture processes, convection, and associated precipitation. Over the past two decades, studies have emphasized the role of western boundary currents in the ocean, such as the Gulf Stream and the Kuroshio Extension, in providing moisture to the atmosphere, thereby intensifying convective activity (e.g., clouds and rain) and storms intensity. While the influence of oceanic mesoscale (~200 km-size) and larger scales on storm tracks is relatively understood, the impact of oceanic submesoscale fronts (~10-20 km-size), characterized by strong sea surface temperature gradients of 5°C per 10 km, remains unknown. Using a global coupled ocean-atmosphere simulation at a km-scale resolution, we show that half of latent heat flux variability at the air-sea interface is driven by oceanic motions at the mesoscale (~40%) and submesoscale (~10-20 km-size, <10%) in the Kuroshio Extension during winter. The analysis further demonstrates that ocean submesoscale fronts drive a secondary circulation, extending above the planetary boundary layer up to 4 km within the troposphere, which enhances diabatic processes and convective precipitations within storms. In the warm sector of storms, ocean submesoscale fronts locally account for half of the total diabatic heating and half of the total precipitations, averaging 14 mm/day over five days. In contrast, diabatic heating and precipitations associated with submesoscale fronts are respectively three and twelve times smaller in the cold sector. As such, ocean submesoscale fronts pump moisture from the ocean to the atmosphere and have the potential to affect storms intensification. Overall, these results suggest that SWOT can identify the influence of ocean fine-scales on weather systems by measuring air-sea exchanges down to the submesoscales.

Reference: Vivant, F., Siegelman, L., Klein, P., Torres, H. S., Menemenlis, D., & Molod, A. M. (2025). Ocean submesoscale fronts induce diabatic heating and convective precipitation within storms. Communications Earth & Environment, 6(1), 69. https://doi.org/10.1038/s43247-025-02002-z