Combined Ocean Tide Analysis by GRACE and Altimetry data (COTAGA)

精确的海潮模型是至关重要的，因为(i)必须从CHAMP和GRACE观测中去除海潮的影响，以便获得专门描述地球重力的重力场模型；（ii）高度计海面高度应该“不受潮汐影响”，以便相互比较并被吸收到数值模型中。即使是在最新的模型中，对大陆架和极地海洋潮汐的不足也是众所周知的。因此，本项目侧重于两种策略：1)对广泛使用的最先进的海潮模型FES2004进行经验改进，(a)仅从GRACE数据（长波）中求解空间分辨率短至300公里的主要潮汐成分的残差(b)将响应和谐波分析应用于多任务高度计数据，以估计特别是浅水区主要潮汐成分的校正和非线性效应，如M4（短波）波长)。这两种修正都将被验证，并结合到一个升级的fes2004模型中，随后用于更精确地消除GRACE重力场模型的混叠，并改进测高数据的修正。2)水动力模拟，进一步完善汉堡潮汐模型。通过对专业知识的修正，这些调查将提供一个具有同化的开阔海和浅海潮汐定量动态模型，能够克服目前潮汐模型的不足。

Precise models of ocean tides are crucial because (i) the effect of ocean tides has to be removed from CHAMP and GRACE observations in order to obtain gravity field models describing exclusively the Earth gravity and (ii) altimetric sea surface heights should be ¿tidefree¿ in order to be comparable with each other and to be assimilated into numerical models. Deficiencies for ocean tides over continental shelves and in polar oceans are well known ¿ even for the most recent models. The present project therefore focuses on two strategies:1) Empirical improvements to the widely used state-of-the-art ocean tide model FES2004 by (a) solving residuals for major tidal constituents with a spatial resolution as short as 300 km from GRACE data only (long wavelength) and (b) applying response and harmonic analysis to multi-mission altimeter data to estimate in particular for shallow water areas corrections for the dominant tidal constituents and non-linear effect like M4 (short wavelength). Both, corrections will be validated and combined to an upgraded FES2004-model subsequently used for a more precise de-aliasing of the GRACE gravity field models and for improved corrections of altimetry data.2) Hydrodynamic modelling to further enhance the Hamburg Tide Model. Revising expertise these investigations shall provide a quantitative dynamical tide modelling with assimilation in open ocean and shallows sea, capable to overcome the deficiencies of current tide models.