Improving ocean tides by constraining the dynamic HAMTIDE model with altimetry an GRACE data

通过高度测量和 GRACE 数据约束动态 HAMTIDE 模型来改善海洋潮汐

• 批准号: 192240048
• 负责人: Professor Dr.-Ing. Reiner Rummel
• 金额: --
• 依托单位: Centrum für Erdsystemforschung und Nachhaltigkeit (CEN)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/192240048?language=en
• 关键词: Improving; ocean; tides; constraining; dynamic

The proposed effort of improving global ocean tide models through the assimilation of tidal information available from altimetry and GRACE data is of central concern for the SPP 1257 “Massentransporte und Massenverteilungen im System Erde” and is necessary to improve GRACE and GOCE gravity field modeling (to avoid aliasing). At the same time the effort will improve our knowledge about the role of tide in the general circulation of the ocean. Global ocean tide models describe short term ocean mass variations, quantify loading effects for stations on land, explain parts of the variations observed in Earth rotation, and are required for correcting altimetric sea surface heights and for GRACE and GOCE gravity field modeling (dealiasing). Equally important, tidal friction, mainly in the shallow seas, contribute to mixing the ocean, and exerts influence on the angular momentum and hence on the length of the day. Moreover, the internal wave drag caused by interaction of barotropic tidal currents with topography induces generation of the internal tides in the deep ocean. Such conversion of the mechanical energy into the internal tides is important for the abyssal ocean mixing to maintain the general ocean circulation (nearly steady-state process). Other important features of the tides are their influence on the solid Earth deformation (loading and self-attraction effect) and on the variation of the gravitational fields, consequently on the variation of the satellite orbits. Improving our understanding of ocean tides and expanding our insight into tidal currents, tidal energy transfer or dissipation is therefore an O(1)-problem to physical oceanography and the geodetic community alike. Improved estimates of ocean tides, beyond what we can learn from empirical tide models, can be obtained by constraining dynamical tide models by observed tidal information. The dataassimilative model HAMTIDE, which is used in this project, has already proven valuable and capable of modelling ocean tides during the first two funding periods of DAROTA. The high quality of the dynamical solution is obtained through an effective method by which the model is being constrained by surface tide information (water elevation defined by the altimetry as well as data inferring tidal currents). Results can be used for detecting rates and generation sites of the surface-to-internal tide conversion, finding regions of the tidally induced vertical mixing, and consequently influence on the climate, i.e., an important link from satellite signals to climate variations. In the next phase, the gravimetry (GRACE, GOCE) and altimetry (T/P, ICESat, CRYOSAT2) data will be used simultaneously as constraints in the assimilation process. This will improve tidal estimates not only in low and mid-latitudes where altimetry is available, but also in high latitudes where better tide models are needed to improve gravity field retrievals. The first result of this kind of data assimilation (with coarse resolution and few gravimetry data) is highly promising. Results will be used for an improved understanding of tidal dissipation (see also the figure on the title page and the attached draft paper Taguchi, Stammer and Zahel, 2010). Results will likewise be intercompared with all state of the art global tide models as part of the proposed effort.

通过同化高度计和 GRACE 数据中提供的潮汐信息来改进全球海洋潮汐模型的建议工作是 SPP 1257“Massentransporte und Massenverteilungen im System Erde”的核心关注点，并且对于改进 GRACE 和 GOCE 重力场模型是必要的（以同时，这一努力将提高我们对潮汐在海洋总体环流中的作用的了解，全球海洋潮汐模型描述了短期海洋质量。变化，量化陆地站的负载效应，解释地球自转中观测到的部分变化，并且是校正高度测量海面高度以及 GRACE 和 GOCE 重力场建模（去混叠）所必需的。潮汐摩擦力同样重要，主要是在潮汐摩擦力中。浅海，有助于混合海洋，并对角动量产生影响，从而影响日的长度。此外，正压潮流与地形相互作用引起的内波阻力导致内波的产生。深海潮汐的这种机械能转化对于深海混合以维持总体海洋环流（近稳态过程）非常重要。潮汐的其他重要特征是它们对固体地球的影响。变形（载荷和自吸引效应）以及引力场的变化，从而提高我们对海洋潮汐的理解，扩大我们对潮汐流、潮汐能的认识。因此，对于物理海洋学和大地测量学界来说，转移或耗散是一个 O(1) 问题。改进的海洋潮汐估计超出了我们从经验潮汐模型中可以学到的知识，可以通过观测到的潮汐信息约束动态潮汐模型来获得。该项目中使用的数据同化模型 HAMTIDE 已被证明具有价值，并且能够在 DAROTA 的前两个资助期间对海洋潮汐进行建模。通过该模型获得了高质量的动力学解决方案。模型受表面潮汐信息（由测高定义的水位以及推断潮汐流的数据）约束的有效方法，结果可用于检测表面潮汐到内部潮汐转换的速率和生成地点，寻找潮汐引起的垂直混合的区域，从而对气候产生影响，即卫星信号与气候变化的重要联系。在下一阶段，重力测量（GRACE、GOCE）和高度测量。 （T/P、ICESat、CRYOSAT2）数据将同时用作同化过程中的约束，这不仅将改善可进行测高的低纬度和中纬度地区的潮汐估计，而且还将改善需要更好潮汐模型的高纬度地区的潮汐估计。改进重力场反演的这种数据同化（具有粗分辨率和少量重力数据）的第一个结果将非常有希望用于改善对潮汐的理解。作为拟议工作的一部分，结果将类似地与所有最先进的全球潮汐模型进行相互比较。