GRACE时变重力场各向异性高斯组合滤波方法

受测量误差等因素影响，直接使用GRACE时变重力场模型的地表质量变化反演结果呈现严重条带噪声，必须采用滤波消除。本文对不同滤波方法进行了试验分析，以信噪比最大为准则，确定了不同滤波方法的最优滤波参数，并在此基础上提出了一种各向异性组合滤波方法。该方法根据时变重力场模型球谐系数误差特性，结合各向异性高斯滤波和均方根滤波特点，对精度较高的低次项系数采用较大权重以保留更多有效信号，而对精度较差的高次项系数采用较小权重以压制噪声。不同于传统的两步法组合滤波，该方法仅需进行一步滤波处理。试验结果表明，本文提出的各向异性组合滤波方法计算步骤简单，能够有效消除条带噪声；与单一滤波和传统两步法组合滤波方法相比，提高了反演结果信噪比，保留了更多真实信号。

Non-isotropic Gaussian combination filtering method of GRACE time-variable gravity

Affected by factors of measurement errors and so on,the surface mass variation inversion results would be dominated by serious north-to-south stripe noise with using time-variable gravity models directly. Filtering methods must be adopted. Optimal parameters of different filtering methods are determined by taking signal-to-noise ratio maximum as the criterion. On this basis, a new non-isotropic combination filtering method is proposed based on the features of time-variable gravity model spherical harmonic serrors. The new non-isotropic combination filtering method is different from traditional two-steps combination filtering methods. It just performs in one step with combining non-isotropic Gaussian filtering and RMS filtering. The basic idea of the new combination filtering method is to apply larger weights to low-order spherical harmonic coefficients while smaller weights to high-order spherical harmonic coefficients for keeping more signals and suppressing noise. The experiment results show that the new combination filtering method is simple to calculate and stripe noise can be removed effectively. The new combination filtering method improves the signal-to-noise ratio compared with previous filtering methods and traditional two-steps combination filtering methods.