Collaborative Research: Exploring centennial changes in ocean circulation with SODA

该项目扩展了一项正在进行的工作(SODA：简单海洋数据同化)，以探索利用平行海洋计划(POP)重建海洋环流百年分析的模式和数据同化的潜力和局限性。该领域是全球海洋，重点放在观测记录更多的上层海洋。主要的时间段是上个世纪下半叶(1950-2007年)，如果能确定在本世纪上半叶有足够的观测数据来提供对海洋状况的可靠估计，则着眼于将其扩展到上个世纪。第一项工作是收集这次再分析所需的观测数据和地面强迫数据。事实上，该项目的动机是气象学家做出的相应努力，以产生百年大气再分析。将对用于同化的信息的错误统计进行彻底调查。第二个努力是探索一种更复杂的基于局部集合变换卡尔曼滤波的同化方案。这一变化将允许数据同化的性质，如温度-盐度误差协方差，在整个再分析期间演变，而不是事先固定。还将把注意力集中在改善混合层结构的表现上。再分析实验的结果将被用来探索各种海洋气候信号的结构和演变，如太平洋的厄尔尼诺、南方涛动(ENSO)和全球海洋的年代际变化。总体目标是探索海洋数据同化在多大程度上可以被用来为海洋产生参考气候，而参考气候反过来又可以作为检查其他物理、化学和生物分析产品的基础，为观测组提供大范围的背景，以及研究海洋？S对气候变化的贡献。智力价值：这项研究将导致对海洋物理状态百年重新分析的潜力的理解，重点放在1000米以上。百年再分析将与强迫和海洋数据集一起编制并提供给社区。学术上的价值在于这种重新分析有可能打开有关海洋的新问题？S在气候变化中所扮演的角色。结果将用于对季节、年际和年代际时间尺度上的变率进行诊断检验，包括检验大气气候变率的协变性。最后，海洋再分析产品将与独立的观测组进行比较，以了解再分析中的不确定性。广泛的影响：来自世界各地的研究人员目前正在使用SODA再分析，由于覆盖时间较长和新的同化计划，应该会对这些新的再分析产生相当大的兴趣。这项工作产生的一系列再分析实验将向社区提供，并将为学生和研究人员提供许多探索海洋气候变异性的机会。除了对马里兰大学和德克萨斯农工大学的研究生进行海洋数据同化方面的培训外，再分析还可以作为其他机构研究生的基础，也可以作为课堂教学的资源。

This project extends an on-going effort (SODA: Simple Ocean Data Assimilation) to explore the potential as well as the limitations of modeling and data assimilation directed toward reconstruction of a centennial analysis of ocean circulation using the Parallel Ocean program (POP). The domain is the global ocean, with an emphasis on the upper ocean where the observational record is more substantial. The main time period is the second half of the last century (1950-2007) with an eye to expand it to the last century if it can established that there are enough observations in the first half of the century to provide reliable estimate of the state of the ocean.. The first effort is to assemble the observations and surface forcing data sets needed for this reanalysis. Indeed, the project is motivated by a corresponding effort by meteorologists to produce a centennial atmospheric reanalysis. A thorough investigation of the error statistics of information that goes into the assimilation will be conducted. The second effort is to explore a change to a more sophisticated assimilation scheme based on the Local Ensemble Transform Kalman Filter. This change would allow properties of the data assimilation such as temperature-salinity error covariances to evolve throughout the reanalysis period, rather than being fixed a priori. Attention will also be focused on improving representation of the structure of the mixed layer. The results of the reanalysis experiments will then be used to explore the structure and evolution of a variety of ocean climate signals such as the El Nino?Southern Oscillation (ENSO) in the Pacific Ocean and decadal variability in the global oceans. The overall goal is to explore the extent to which ocean data assimilation may be used to produce a reference climate for the oceans that in turn can serve as the basis for examining other physical, chemical, and biological analysis products, for providing the large-scale context for observation sets, as well as for studies of the ocean?s contribution to climate variability.Intellectual merit: This research will result in understanding of the potential of a centennial reanalysis of the physical state of the ocean with emphasis on the upper 1000m. Centennial reanalyses will be produced and made available to the community, along with the forcing and ocean data sets. The intellectual merit lies in the potential of this kind of reanalysis to open up new questions regarding the ocean?s role in climate variability. The results will be used to carry out diagnostic examination of variability on seasonal, interannual, and decadal timescales including examination of covariations of atmospheric climate variability. Finally, the ocean reanalysis product will be compared to independent observation sets in order to learn about the uncertainties in the reanalysis.Broader impacts: SODA reanalyses are currently being used by researchers from around the world and there should be considerable interest in these new reanalyses, both because of the longer period of coverage and because of the new assimilation scheme. The set of reanalysis experiments resulting from this work will be made available to the community and will offer many opportunities for students and researchers to explore ocean climate variability. In addition to training graduate students at the University of Maryland and at Texas A&M University in ocean data assimilation, the reanalysis can be used as the foundation for graduate students at other institutions and as a resource for classroom teaching.