Exceptional multi-year prediction skill of the Kuroshio Extension in the high-resolution CESM decadal prediction system

The Kuroshio Extension (KE) has far-reaching influences on climate as well as on local marine ecosystems. Thus, skillful multi-year to decadal prediction of the KE state and understanding sources of skill are valuable. Retrospective forecasts using the high-resolution CESM show exceptional skill in predicting KE variability up to lead year 4, substantially higher than the skill found in a similarly configured low-resolution CESM. The higher skill is attained because the high-resolution system can more realistically simulate the westward Rossby wave propagation of initialized ocean anomalies in the central North Pacific and their expression within the sharp KE front, and does not suffer from spurious variability near Japan present in the low-resolution CESM that interferes with the incoming wave propagation. These results argue for the use of high-resolution models for future studies that aim to predict changes in western boundary current systems and associated biological fields.

黑潮延伸区（KE）对气候及当地海洋生态系统的影响深远。因此，对KE状态进行多年至十年期的精确预测，以及理解预测能力之源，具有重要的价值。利用高分辨率CESM模型进行的回顾性预测显示，在预测KE变率直至提前4年时具有卓越的预测能力，显著高于配置相似但分辨率较低CESM的预测能力。这种更高的预测能力得以实现，是因为高分辨率系统能更真实地模拟初始化于中北太平洋中心的海洋异常的西向罗斯比波传播，及其在黑潮锋面内的表现，且不受低分辨率CESM中近日本地区的虚假变率的干扰，这种虚假变率会干扰 incoming wave propagation。这些结果为使用高分辨率模型进行未来研究提供了论据，这些研究旨在预测西边界流系统及其相关生物领域的变迁。