Haiyuan Yang, Zhaohui Chen, Shantong Sun, Mingkui Li, Wenju Cai, Lixin Wu, Jinzhuo Cai, Bingrong Sun, Ke Ma, Xiaohui Ma, Zhao Jing, Bolan Gan
Published in Geophysical Research Letters, January 2024
Air-sea exchanges across oceanic fronts are critical in powering cloud formation, precipitation, and atmospheric storms. Oceanic submesoscale fronts of scales 1–10 km are characterized by strong sea surface temperature (SST) gradients. However, it remains elusive how submesoscale fronts affect the overlying atmosphere due to a lack of high-resolution observations or models. Based on rare high-resolution in situ observations in the Kuroshio Extension region, we quantify the air-sea exchanges across an oceanic submesoscale front. The cross-front SST and turbulent heat flux gradients reaches 2.4°C/km and 47 W/m2/km, respectively, far stronger than that typically found in mesoscale-resolving products. The stronger SST gradient drives substantially stronger air-sea fluxes and vertical mixing than mesoscale fronts, enhancing cloud formations. The intense air-sea exchanges across submesoscale fronts are confirmed in idealized model simulations, but not resolved in mesoscale-resolving climate models. Our finding provides essential knowledge for improving simulations of cloud formation, precipitation, and storms in climate models.
Fig. Observed atmosphere response to submesoscale front. (a) Sea surface height anomaly field (shading) and surface wind (vector). (b) SST (red) and THF (blue) across the front. (c) Comparison of the SST gradient and heat flux gradient from observation and other products. The SST and heat flux gradients in observations are calculated based on the average between 39.08°N and 39.11°N. The error bars indicate the standard deviation. (d) Relative humidity (%; shading), potential temperature (°C; contour), MABL (black dotted line) and cloud base (gray dots). The black triangle denotes the position of front. Observations reveal large SST and THF gradients across the submesoscale front, which are not resolved in the widely used data and drive a strong cross-front gradient in the MABL.
Yang, H., Chen, Z., Sun, S., Li, M., Cai, W., Wu, L., et al. (2024). Observations reveal intense air-sea exchanges over submesoscale ocean front. Geophysical Research Letters, 51, e2023GL106840. https://doi.org/10.1029/2023GL106840