A Madden–Jillian oscillation (MJO) and boreal summer intraseasonal oscillation (BSISO) are important climate variabilities, which affect a forecast of weather and climate. In this study, the MJO and the BSISO hindcasts from the Global Seasonal Forecast System, version 5 (GS5) were diagnosed using dynamic-oriented theories. We additionally analyzed the GS5 climatological run to identify whether the weakness of the GS5 hindcast results from the model physics or initialization processes. The GS5 hindcast captures three-dimensional dynamics and thermodynamics structure of MJO eastward propagation well in the Indian Ocean. The model produces the boundary layer (BL) moisture convergence anomalies to the east of the MJO deep precipitation with easterly anomalies associated with the Kelvin wave. The enhanced BL moisture convergence increases upward transport of moisture from the surface to the lower troposphere, inducing the moist lower troposphere and the positive convective instability by destabilization of the lower atmosphere and, thus, generating the next convection to the east of MJO deep convection and promoting MJO eastward propagation. However, the signal for eastward propagation is relatively weak in the Maritime Continent (MC) and the Western Pacific (WP). To improve the MJO eastward propagation in the MC and WP, improved heating induced by shallow (or congestus) clouds interacting with enhanced BL dynamics may be required. On the other hand, the GS5 hindcast reproduces the BSISO northward propagation reasonably well in the Indian Ocean, which is attributed to positive vorticity anomalies induced by strong vertical shear.

中文翻译：

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使用面向动态的ISO理论从GloSea5诊断ISO预测

Madden-Jillian振荡（MJO）和夏季北方季节内振荡（BSISO）是重要的气候变化，影响天气和气候的预测。在这项研究中，使用面向动态的理论诊断了来自全球季节预报系统第5版（GS5）的MJO和BSISO后发事件。我们还分析了GS5的气候运行过程，以确定GS5后代的弱点是来自模型物理学还是初始化过程。GS5的后预报捕获了印度洋MJO向东传播井的三维动力学和热力学结构。该模型产生了MJO深降水以东的边界层（BL）湿气收敛异常，以及与开尔文波相关的东风异常。增强的BL水分会聚增加了水分从地表到对流层较低层的向上输送，通过使低层大气不稳定而引起了潮湿的对流层下层和正对流不稳定性，从而在MJO深对流东部产生了下一个对流，促进MJO向东传播。但是，在海陆（MC）和西太平洋（WP）中，向东传播的信号相对较弱。为了改善MJO在MC和WP中的向东传播，可能需要改善由浅（或拥挤）云与增强的BL动力学相互作用而引起的热量。另一方面，GS5的后播在印度洋上较好地再现了BSISO向北的传播，这归因于强垂直切变引起的正涡度异常。