时变卫星重力和频率依赖响应的日长变化激发理论在若干全球动力学的联合应用

Due to mantle anelasticity, oceanic dissipation and quasi-fluid rheology, the Earth’s responses to external perturbations are frequency-dependent and dissipative. Thus Love numbers are actually complex functions of frequency, while traditional length-of-day (LOD) theory treats them as real constants, which will inevitably give rise to discrepancies between theoretical predictions and observations. Therefore, it is necessary to overcome the “constant response assumption” in the traditional theory and develop a new theory to incorporate the effects of frequency-dependent responses. On the other hand, mass migrations and relative motions caused by changes in atmosphere, oceans and continental water are able to cause multi-band LOD variations. However, data qualities for those mass migrations and relative motions are significantly affected by the number and distribution of the observatories, the limitations in numerical simulation models as well as the violation of global mass conservation. High-accuracy LOD observations and satellite time-variable gravity data can place strong constraints on those mass migrations and relative motions, and thus help to improve their accuracies and provide better understandings of them. Meteorological excitations of LOD can be accurately quantified on the bases of the new LOD theory and the refined atmospheric, oceanic and hydrological data for mass migrations and relative motions.

传统日长变化激发理论假定地球介质对外部扰动的响应不随频率变化，实际上地幔滞弹性、海洋耗散性、地球的似流体形变及核幔耦合使该响应表现出明显的频率依赖性和耗散性，导致理论预测与观测的不一致。因此有必要改进传统理论，研究顾及频率依赖响应的日长变化激发理论。大气、海洋、陆地水和冰川的质量迁移和运动可激发多频段的日长变化。由于观测台站数量及分布的限制、相关数值模型的局限性及未考虑全球质量守恒等原因，不同机构发布的相关模型数据存在较大误差，有必要利用高精度的极移观测数据和GRACE/SLR卫星重力数据作为约束，融合不同机构模型数据以提高其精度，深入研究大气、海洋、陆地水和冰川质量迁移和运动规律。基于顾及频率依赖响应的日长变化激发理论及改进的大气、海洋、陆地水和冰川数据，可更为精准地确定多频段日长变化的激发机制。

本项目取得的成果可归纳如下：.1、确定了高精度的地球动力学形状参数 (包括地球、地幔及地核的主惯性矩及动力学扁率)。.2、研究了冰川均衡调整GIA对重力和地表形变的影响，并利用全球GPS速度场确定的GIA地表形变反演改进了地幔粘滞度模型，并据此导出了顾及地幔黏弹性的Love数改正公式。.3、提出了一种自洽的、根据极移观测估算Chandler晃动周期TCW和品质因子QCW的新方法，得到了最优的TCW和QCW估值，并据此导出了顾及地幔滞弹性的Love数改正公式。.4、导出了顾及地幔滞弹性、地幔黏弹性和海潮耗散性的、频率依赖的Love数理论公式，建立了顾及地球频率依赖响应的日长变化激发理论。.5、确定高精度的全球大气、海洋及陆地水物质迁移和运动数据模型LDCmgm90，并揭示大气、海洋及陆地水的变化规律；提供了对应于该模型的全球地表负荷形变模型LDCmgm90-loading。.6、在顾及地球频率依赖响应的情况下，采用小波等手段分析了大气、海洋及陆地水变化对多频段日长变化的激发作用。.7、基于Langrage乘子法，提出了频域最小差异法LDC的改进方法LMFDC法，可更好的融合多源数据，改进数据质量。.8、基于Holt-Winters算法，提出了一种考虑Chandler晃动衰减和激发作用的地球自转参数（EOP）预报方法HW-VCW。该方法单独使用已达到或超过目前主流的多种组合EOP预报方法的精度水平。.9、提出了一种结合频域和时域Liouville方程的、可严密结算地球自转观测激发的时频结合法FTLE。该方法在时域和频域均优于IERS官方程序。