Analysis of heat transport driven by the Kuroshio and short-range forecast of the Kuroshio variabilities using data assimilation methods

对日本南部黑潮路径变率的短期预报能力进行了研究，将绝对海面动态高度资料同化到一个高分辨率的1 1/2层原始方程模式中，从1993年到1997年连续5年。所用的初始化方案是变分方法，它包含模式的非线性动力学作为弱约束，适用于西部边界流区的初始化。分析场的时间序列很好地反映了研究期间的黑潮路径变化，例如，在Enshu-nada外海流轴的纬度位置与观测值的均方根偏差在0.3°以内，而它们的观测均方根变率为0.5°。然后进行了116例90天的黑潮路径变化的预报试验，以评估我们同化系统的统计特性。我们f…的精确度日本南部更多的预报场远高于持续性试验，并且在初始化后成功地再现了黑潮向Enshu-nada外大范围路径演变的典型过程。特别是，向东推进的速度和曲流河的水平尺度与观测结果非常相似。这些结果以及与分析场均方根变率的比较，使我们能够推断出日本南部黑潮路径变率的大约60天预报是可能的。其次，为了估计黑潮的总热量输送，我们利用海洋环流模式和伴随方法建立了一个4D-VAR海洋数据同化系统。结果证明了该再分析数据的有效性。例如，对黑潮路径进行了修正，使之更加逼真，太平洋表面热通量再分析数据代表了过去研究中大多数熟悉的总体特征。这些改进使我们能够通过我们的数据同化系统来充分估计黑潮热量输送。较少

Capability for short-range forecasting of the Kuroshio path variabilities south of Japan is studied by assimilating the absolute sea surface dynamic height data into a high-resolution 1 1/2-layer primitive equation model for 5 years from 1993 to 1997. The initialisation scheme used is the variational method, which contains the nonlinear dynamics of the model as a weak constraint and is suitable for initialization in the western boundary current regions.The time series of the analysis field well represents the-Kuroshio path variations during the study period For example, the rms differences from the observations falls within 0.3°for the location in latitude of the current axis off Enshu-nada while their observed rms variability is 0.5°By using the resulting fields as the initial conditions, one hundred and sixteen cases of 90-day forecast experiments for the Kuroshio path variations are then performed to assess the statistical properties of our assimilation system. The accuracy of our f … More orecasted field south of Japan is much higher than that of persistence experiments and the typical evolution of the Kuroshio into a large-amplitude path off Enshu-nada is successfully reproduced after the initialization. In particular, the eastward progression speed and the horizontal scale of the meander are quite similar to those observed. These results and the comparison with the rms variability of the analysis field enable us to infer that roughly 60-day forecasts of the Kuroshio path variabilities south of Japan are possible.Next, in order to estimate the total heat transport by the Kuroshio, we have constructed a 4D-VAR ocean data assimilation system using an ocean general circulation model and the adjoint method. The result demonstrates the validity of this reanalysis data. For example, the Kuroshio path is corrected to be more realistic and the surface heat flux reanalysis data in the Pacific Ocean represents most of the familiar gross features of past studies. These improvements allow us to estimate the Kuroshio heat transport adequately by our data assimilation system. Less