A new weakly coupled data assimilation (CDA) system based on the dimension‐reduced projection four‐dimensional variational data assimilation (DRP‐4DVar) with a simplified off‐line localization technique and a fully coupled model, i.e., the Grid‐point Version 2 of Flexible Global Ocean‐Atmosphere‐Land System Model (FGOALS‐g2), was developed for the initialization of decadal predictions. A 1‐month assimilation window was adopted for the CDA system, in which monthly mean temperature and salinity analyses were assimilated along the trajectory of the coupled model during the initialization for the period of 1945–2006. The system is efficient because the 62‐year initialization only takes about 2.375 times of the time cost of the uninitialized run for the same period. Compared with the uninitialized simulation and the initialization without localization, ocean temperature and salinity, sea surface elevation, surface air temperature, and precipitation are in better agreement with the verification data. Furthermore, climate variabilities in the Pacific and Atlantic regions such as El Niño‐Southern Oscillation, Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) are more realistically captured. Starting from the initial conditions (ICs) generated by the initialization, 10‐member ensemble decadal prediction experiments were conducted each year from 1961 to 1996. The results demonstrate that higher decadal prediction skills of surface air temperature anomalies averaged over the globe, ocean, land, and the North Pacific subpolar gyre are achieved than those obtained from persistence, the uninitialized simulation, and the prediction initialized from the ICs without localization. Besides, PDO and AMO indices exhibit significant correlation skills in most lead times.

中文翻译：

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基于DRP-4DVar的耦合数据同化系统，具有简化的离线定位技术，可进行十进制预测

一种新的弱耦合数据同化（CDA）系统，它基于降维投影四维变分数据同化（DRP-4DVar），具有简化的离线定位技术和完全耦合的模型，即网格点版本2开发了灵活的全球海洋-大气-陆地系统模型（FGOALS-g2），用于初始化年代际预测。CDA系统采用了1个月的同化窗口，其中在1945年至2006年初始化期间，沿耦合模型的轨迹对月平均温度和盐度分析进行了同化。该系统之所以有效，是因为62年的初始化仅花费了同期未初始化运行时间成本的2.375倍。与未初始化的模拟和未本地化的初始化相比，海洋温度和盐度，海面海拔，地表气温和降水与验证数据更好地吻合。此外，更现实地捕捉了太平洋和大西洋地区的气候变化，例如厄尔尼诺-南方涛动，太平洋年代际涛动（PDO）和大西洋多年代际涛动（AMO）。从初始化产生的初始条件（IC）开始，从1961年到1996年，每年进行10个成员的年代际预测实验。结果表明，全球，海洋，陆地的平均地表温度异常的年代际预测技能更高，而北太平洋副极回旋比通过持续性，未初始化的模拟获得的回旋要好，并从IC初始化预测而无需本地化。此外，PDO和AMO指数在大多数交货时间内都显示出显着的相关技能。