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Improved estimates of heat and water mass transports in the Pacific Ocean by a long-term data assimilation experiment using a 4-dimensional variational approach

通过使用 4 维变分方法的长期数据同化实验改进了对太平洋热量和水团传输的估计

基本信息

批准号：
14340141
负责人：
AWAJI Toshiyuki
金额：
$ 9.28万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The main objective of our research is to construct an innovative 4-dimensional variational(4D-VAR) data assimilation system capable of providing high-quality comprehensive datasets. Synthesis of observational data and state-of-the-art general circulation models by the variational approach has the ability to produce a dynamically self-consistent space-time dataset. Such datasets are urgently required for more accurate prediction and for better estimation of the dynamical state of the Pacific Ocean associated with global warming.In order to achieve our goal, we have successfully constructed a 4D-VAR data assimilation system on a parallel computer machine, and have applied it to a long-term reanalysis experiment during the period after the late 1980's. This experiment assimilated all the observational data available into an ocean general circulation model. The obtained reanalysis dataset shows good consistency with previous knowledge of important climate events. For example, the evolution … More of Nino3 SST is well reproduced (its error value reduces to about 1/2 of that from the earlier simulations), which supports the notion that our dataset accurately represents the climate variability in this region. Further, our reanalysis dataset exhibits realistic subsurface water mass distribution and enables us to clarify the water mass formation and movement processes. An application of a sensitivity experiment to the dichothermal and mesothermal water pathways that characterize the northwest North Pacific circulation is performed in which we investigate the sensitivity to an artificial cost given in the subarctic Pacific region. The distribution of adjoint variables shows good consistency with previous studies of the subtropical Kuroshio Extension region and western subarctic region. Similarly, intermediate waters can be traced back to their source regions. Using our reanalysis data set, we estimated meridional heat and water mass transports associated with the overturn in the Pacific Ocean. A close look at the meridional distributions reveal that the annual mean and the seasonal change are by and large consistent with previous knowledge. These results confirm that our 4D-VAR data assimilation system is a powerful tool for the understanding and prediction of the dynamical state of the Pacific Ocean. Less

本研究的主要目标是建立一个创新的四维变分（4D-VAR）数据同化系统，能够提供高质量的综合数据集。通过变分方法合成观测数据和最先进的大气环流模式，能够产生动态自洽的时空数据集。为了更准确地预报和更好地估计与全球变暖有关的太平洋动力状态，我们在并行计算机上成功地建立了一个4D-VAR数据同化系统，并将其应用于80年代后期以后的长期再分析试验。这项试验将所有现有的观测数据纳入海洋环流模式。所获得的再分析数据集显示出良好的一致性与以前的知识的重要气候事件。例如， ...更多信息 Nino 3 SST的模拟结果较好地再现了Nino 3 SST的变化（误差值约为前期模拟结果的1/2），这支持了我们的资料准确地反映了该地区气候变率的观点。此外，我们的再分析数据集表现出现实的地下水质量分布，使我们能够澄清水团的形成和运动过程。应用的敏感性实验的dichothermal和中层水的途径，西北北太平洋环流的特点是，我们调查的敏感性，在亚北极太平洋地区的人工成本。伴随变量的分布与前人对副热带黑潮延伸区和副北极西部的研究结果有较好的一致性。同样，中间沃茨也可以追溯到它们的源区。利用我们的再分析数据集，我们估计了与太平洋翻转相关的纬向热量和水质量输送。仔细研究的纬向分布表明，年平均值和季节变化基本上与以前的知识一致。这些结果表明，我们的4D-VAR资料同化系统是一个强大的工具，为了解和预测的动力状态的太平洋。少