A DRP-4DVar-Based Coupled Data Assimilation System With a Simplified Off-Line Localization Technique for Decadal Predictions
A DRP-4DVar-Based Coupled Data Assimilation System With a Simplified Off-Line Localization Technique for Decadal Predictions
复制标题
基于 DRP-4DVar- 的耦合数据同化系统，具有简化的十年预测离线定位技术
DOI：
10.1029/2019ms001768
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发表时间：
2020
影响因子：
6.8
通讯作者：
Yu Yongqiang
中科院分区：
文献类型：
--
作者：
He Yujun;Wang Bin;Liu Li;Huang Wenyu;Xu Shiming;Liu Juanjuan;Wang Yong;Li Lijuan;Huang Xiaomeng;Peng Yiran;Lin Yanluan;Yu Yongqiang
基于简化脱机定位技术的降维投影四维变分数据同化（DRP-4DVar）和全耦合模式，即柔性全球海洋-大气-陆地系统模式（f目标-g2）格点版2，建立了一个用于年代际预测初始化的弱耦合数据同化（CDA）系统。CDA系统采用1个月同化窗，同化窗内逐月平均温度和盐度分析沿耦合模式初始化轨迹同化，同化时间为1945-2006年。系统的效率很高，因为62年的初始化运行时间仅为未初始化运行时间的2.375倍。与未初始化和初始化不定位的模拟结果相比，海洋温度和盐度、海面高程、地面气温和降水与验证数据更吻合。此外，太平洋和大西洋地区的气候变化，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），更真实地捕捉到了。从初始化产生的初始条件（initial conditions, ICs）开始，1961 ~ 1996年每年进行10元集合年代际预测试验。结果表明，对全球、海洋、陆地和北太平洋次极环流平均地表气温异常的年代际预测能力高于持续、未初始化模拟和非局域化ic初始化预测。此外，PDO和AMO指数在大部分交货期均表现出显著的相关技能。
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 Nino-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.