面向海洋重力场反演的新型测高任务波形重跟踪算法研究

Satellite altimetry has evolved as an effective method for recovering refined marine gravity field, and corresponding researches have always been a hot issue in the geoscience community. However, the constructed marine gravity models are slowing down their rates of enhancement in accuracy and resolution due to the restriction of Ku-band pulse-limited measurements. The new-generation altimetry missions with special design in measuring mode (e.g. SAR) and measuring frequency (e.g. Ka-band) bring great potential for improving marine gravity recovery, which also represent the direction of future development. One emerging problem is that the current retrackers are no longer suitable for Ka-band and SAR-mode echoes with parameters and threshold values optimally determined for Ku-band measurements. Consequently, we intend to develop an improved waveform retracker for new-generation altimetry missions with the purpose of optimal gravity recovery. The Ka-band and SAR-mode waveforms are firstly divided into groups on the basis of cluster analysis and regularities of echo power will be discussed according to the sampling analysis. The model-fitting parameters and the empirical threshold values are respectively determined for each classified group. An improved strategy is proposed for selecting a better result from either the model-fitting algorithm or the empirical threshold method. The enhancement of accuracy and resolution capability for Ka-band and SAR-mode altimetry measurements based on the retracker will be verified according to the crossover analysis, the validation with tide gauge data, the calculation of vertical deflections and the constructed regional marine gravity models. This research is helpful for exploring the detail characteristics of marine gravity field and especially effective in the coastal zone. The acquired results also play an important role in refining the marine geoid information in the offshore regions.

卫星测高技术是反演海洋重力场的主要手段。目前，受传统Ku波段观测方式的制约，反演的海洋重力场模型精度和分辨率趋于瓶颈。Ka波段和SAR模式等观测技术是未来测高任务的发展方向，有望在精度和分辨率上带来新的改善，但同时也对测高波形重跟踪算法带来新的需求。因此，本项目瞄准近岸海洋重力场反演精度和分辨率问题，将针对Ka、SAR等新型测高模式的波形观测数据，利用聚类分析等方法研究波形的分类，分析波形采样功率分布特征，获取针对不同重跟踪算法的适用波形判定准则，进而研究波形拟合参数的确定和重跟踪经验阈值的选取等，发展面向海洋重力场反演的新型测高任务波形重跟踪算法，并通过交叉点统计、验潮资料检核、垂线偏差解算和区域重力场建模，验证新型测高资料和波形重跟踪算法的可靠性。本项目的研究有助于提高海洋重力场反演，特别是近岸区域的精度和分辨率水平，为海岸带大地水准面精化等提供精细数据保证。

卫星测高技术是反演海洋重力场的主要手段。目前，受传统Ku波段观测方式的制约，反演的海洋重力场模型精度和分辨率趋于瓶颈。Ka波段和SAR模式等观测技术是未来测高任务的发展方向，有望在精度和分辨率上带来新的改善，但同时也对测高波形重跟踪算法带来新的需求。本项目针对这一问题，开展面向海洋重力场反演的新型测高任务波形重跟踪算法研究，具体研究内容包括：.（1）完成了Ka波段测高任务波形资料的采样功率分布特征分析，发展了两步加权最小二乘拟合法，通过迭代选取最优拟合参数和截取子波形提升拟合效率；在此基础上，通过标准差分析、功率谱分析和模型检核评价，验证了新算法的波形重跟踪效果。.（2）完成了CryoSat-2 SAR模式测高任务波形资料的采样功率分布特征分析，实现了波形特征参数计算和波形分类；分别基于抛物柱函数模型拟合法和NPP阈值法实现波形重跟踪过程，南海海域算例表明采用抛物柱函数模型拟合的波形重跟踪算法效果更优。.（3）实现了单星及多星垂线偏差法解算海洋重力异常的流程，以西北大西洋海域作为研究算例，验证了Ka波段、SAR模式等新型测高任务波形资料及其适用的波形重跟踪算法带来了海洋重力场反演水平的提升，同船测资料检核的标准差缩减了约10%。. 总体而言，本项目的研究成果推进了新型测高任务波形资料重跟踪方法的改进，促进了海表面高度观测精度的提升，有利于精化卫星测高资料的探测能力，为海洋重力场反演应用等提供精细数据保证。