Role of Ocean Initialization in Skillful Prediction of Sahel Rainfall on the Decadal Timescale
Role of Ocean Initialization in Skillful Prediction of Sahel Rainfall on the Decadal Timescale
复制标题
海洋初始化在十年时间尺度萨赫勒降雨巧妙预测中的作用
DOI：
10.1175/jcli-d-21-0729.1
复制
发表时间：
2022-12
影响因子：
4.9
通讯作者：
Feifei Li
中科院分区：
文献类型：
--
作者：
Yujun He;Bin Wang;Lijuan Li;Juanjuan Liu;Yong Wang;Feifei Li
摘要：20世纪70年代至80年代，萨赫勒地区夏季降雨持续干旱，造成严重的人员生命和经济损失。许多研究指出，萨赫勒降雨的年代际变化主要受不同洋盆低频海面温度（SST）变化的调节。然而，这种调制如何有助于萨赫勒降雨的十年预测技能仍然未知。这项研究使用降维投影四维变分 (DRP-4DVar) 数据同化方法初始化的十年后报提供了肯定的响应，仅将海洋分析数据纳入灵活的全球海洋-大气-陆地系统模型 (FGOALS-g2) 的网格点版本 2 中。后报揭示了 DRP-4DVar 方法对于提高通过异常相关系数 (ACC)、均方根误差、ACC 差异和均方技能得分来衡量的萨赫勒降雨年代际预测技能的好处。大西洋、地中海、印度洋和太平洋海温的年代际变化以及相关萨赫勒降雨与海温关系的正确表示都得到了很好的预测，从而对萨赫勒降雨进行了巧妙的预测。特别是，与其他流域相比，大西洋和地中海海温的初始化在萨赫勒降雨的熟练预测中发挥着更重要的作用。 FGOALS-g2预测系统对萨赫勒降雨的预测能力明显高于大多数仅用海洋分析数据初始化的耦合模式比对项目（CMIP5&6）第五和第六阶段预测系统的预测能力。这一结果可能归因于 FGOALS-g2 预测系统比 CMIP5&6 预测系统在萨赫勒降雨量和海温之间的关系更准确。
Abstract.Sahel summer rainfall has undergone persistent drought from the 1970s to 1980s, causing severe human life and economic losses. Many studies pointed out that the decadal variations of Sahel rainfall are mainly modulated by low-frequency sea surface temperature (SST) variations in different ocean basins. However, how this modulation contributes to the decadal prediction skill of Sahel rainfall remains unknown. This study provided an affirmative response using the decadal hindcasts initialized by a Dimensional-Reduced Projection Four-Dimensional Variational (DRP-4DVar) data assimilation method to incorporate only ocean analysis data into the Grid-point Version 2 of the Flexible Global Ocean-Atmosphere-Land System Model (FGOALS-g2). The hindcasts reveal the benefits of the DRP-4DVar approach for improving the Sahel rainfall decadal prediction skill measured by the anomaly correlation coefficient (ACC), root mean square error, ACC difference and mean square skill score. The decadal variations of SSTs in the Atlantic, Mediterranean Sea, Indian Ocean, and Pacific as well as correct representations of the associated Sahel rainfall-SST relationships are well predicted, thus leading to skillful predictions of Sahel rainfall. In particular, the initialization of SSTs in the Atlantic and Mediterranean Sea plays a more important role in skillful Sahel rainfall predictions than in the other basins. The prediction skill of Sahel rainfall by the FGOALS-g2 prediction system is significantly higher than those by most fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5&6) prediction systems initialized only with ocean analysis data. This result is likely attributed to a more accurate relationship between Sahel rainfall and SST by the FGOALS-g2 prediction system than by the CMIP5&6 prediction systems.