地球时变重力场模型反演陆地水储量变化已为全球气候变化研究作出巨大贡献, 考虑到时变重力场模型球谐系数中存在相关性, 其高阶次项具有较大的误差, 需采用最优的滤波方法进行空间平滑。本文提出一种新的各向异性组合滤波方法, 其基本思想是将改进的高斯滤波法与均方根(root mean square, RMS)滤波法组合, 即对球谐系数的低阶次采用改进的高斯滤波法, 而高阶次采用RMS滤波法。首先分析了最新的GRACE RL05系列时变重力场模型系数误差特性, 基于全球水储量变化反演结果, 分析比较了高斯滤波、改进的高斯滤波、RMS滤波和DDK滤波与本文提出的组合滤波法的有效性及精度, 并利用模型结果进行验证, 计算结果表明, 组合滤波法的中误差最小。研究结果表明, 本文提出的组合法相比于先前的滤波方法, 可有效地过滤高阶次的噪声, 消除南北条带误差, 同时减少信号泄漏, 提高信噪比, 保留更多有效的地球物理信号, 进而提高反演精度。
[1] TAPLEY B D, BETTADPUR S, WATKINS M, et al. The Gravity Recovery and Climate Experiment: Mission Overview and Early Results[J].Geophysical Research Letters, 2004, 31:1-4.
[2] YADU N, POKHRE L, HANASAKI N, et al. Model Estimates of Sea-level Change due to Anthropogenic Impacts on Terrestrial Water Storage[J]. Nature Geoscience, 2012(5):389-392.
[3] HU Xiaogong, CHEN Jianli, ZHOU Yonghong. Monitoring Seasonal Changes in the Yangtze River Water Storage by GRACE Space Observations[J]. Science in China Series D Earth Sciences, 2006, 36(3): 225-232. (胡小工, 陈剑利, 周永宏.利用GRACE 空间重力测量监测长江流域水储量的季节性变化[J]. 中国科学D 辑, 2006, 36(3): 225-232.)
[4] ZHOU Xuhua, WU Bing, PENG Bibo, et al. Detection of Global Water Storage Variation Using GRACE. Chinese[J].Chinese Journal of Geophysics, 2006, 49(6):1644-1650. (周旭华, 吴斌, 彭碧, 等. 全球水储量变化的GRACE卫星检测[J]. 地球物理学报, 2006, 49(6): 1644-1650.)
[5] LUO Zhicai, LI Qiong, ZHONG Bo. Water Storage Variations in Heihe River Basin Recovered from GRACE Temporal Gravity Field[J]. Acta Geodaetica et Cartographica Sinica, 2012, 41(5):676-681. (罗志才, 李琼, 钟波.利用GRACE时变重力场反演黑河流域水储量变化[J]. 测绘学报, 2012, 41(5): 676-681.)
[6] DUAN Jianbin, ZHONG min, YAN Hanming, et al. Recovery of Land Water Storage Variations in Chinese Mainland by Use of GRACE Data[J]. Journal of Geodesy and Geodynamics, 2007, 27(3): 68-71. (段建宾, 钟敏, 闫昊明, 等, 利用重力卫星观测资料解算中国大陆水储量变化[J]. 大地测量与地球动力学, 2007, 27(3): 68-71.)
[7] ZHU Guangbin, LI Jiancheng, WEN HanJiang, et al. Study On Variations of Global Continental Water Storage With GRACE Gravity Field Models[J]. Journal of Geodesy and Geodynamics, 2008, 28(5): 39-44. (朱广彬, 李建成, 文汉江,等. 利用GRACE时变重力位模型研究全球陆地水储量变化[J]. 大地测量与地球动力学, 2008, 28(5): 39-44.)
[8] ZHAI Ning, WANG Zeming, WU Yue, et al. Recovery of Yangtze River Basin Water Storage Variations by GRACE Observations[J]. Geomatics and Information Science of Wuhan University, 2009, 34(4): 436-439.(翟宁, 王泽民, 伍岳, 等. 利用GRACE 反演长江流域水储量变化[J]. 武汉大学学报:信息科学版, 2009, 34(4): 436-439.)
[9] WAHR J, MOLENAAR M, BRYAN F. Time Variability of the Earth's Gravity Field: Hydrological and Oceanic Effects and Their Possible Detection Using GRACE[J]. Journal of Geophysical Research, 1998,103:30205-30229.
[10] JEKELI C. Alternative Methods to Smooth the Earth's Gravity Field[R].Columbus:Department of Geodetic Science and Surveying. Ohio State University,1981.
[11] SWENSON S, WAHR J. Methods for Inferring Regional Surfacemass Anomalies from Gravity Recovery and Climate Experiment (GRACE) Measurements of Time-variable Gravity[J]. Journal of Geophysical Research, 2002, 107(B9):1-27.
[12] HAN S C, SHUM C K, JEKELI C, et al. Non-isotropic Filtering of GRACE Temporal Gravity for Geophysical Signal Enhancement[J].Geophysical Journal International, 2005, 163:18-25.
[13] CHEN J L, WILSON C R, SEO K. Optimized Smoothing of Gravity Recovery and Climate Experiment (GRACE) Time-variable Gravity Observations[J]. Journal of Geophysical Research, 2006,DOI:10.1029/2005JB004064.
[14] KUSHE J. Approximate Decorrelation and Non-isotropic Smoothing of Time-variable GRACE-type Gravity Field Models[J].Journal of Geodesy, 2007, 81:733-749. DOI:10.1007/s00190-007-0143-3.
[15] KUSHE J, SCHMIDT R, PETROVIC S,et al. Decorrelated GRACE Time-variable Gravity Solutions by GFZ, and Their Validation Using a Hydrological Model[J]. Journal of Geodesy, 2009,83(10):903-913.
[16] RODELL M, HOUSER P R, JAMBOR U, et al. The Global Land Data Assimilation System[J]. Bulletin of the American Meteorological Society, 2004,85 (3):381-394.
[17] FAN Y, VANDE H, MITCHELL K, et al. A 51-Year Reanalysis of the US Land-surface Hydrology [J]. GEWEX News, 2003, 13(2): 6-10.
[18] FUKUMORI I, RAGHUNATH R, FU L, et al. Assimilation of TOPEX/POSEIDON Data into a Global Ocean Circulation Model: How Good are the Results?[J]. Journal of Geophysical Research, 1999, 104(C11), 25647-25665.
[19] HEISKANEN W A, MORTIZ H. Physical Geodesy[M].San Francisco: Freeman and Company, 1967.
[20] PELTIER W R, ANDREW J. Glatial Isostatic Adjustment. I: The forward Problem[J]. Geophy. Journal of Geophysical Research, 1976, 46, 605- 646.
[21] SWENSON S, WAHR J, MILLY P. Estimated Accuracies of Regional Water Storage Variations Interfered from the Gravity Recovery and Climate Experiment (GRACE)[J]. Water Resource Research, 2003, 39(8),DOI:10.1029/2002WR001808.
[22] CHEN J L, WILSON C R, BLANKENSHIP D D,et al. Antarctic Mass Rates from GRACE[J]. Geophysical. Research. Letters, 2006c, 33,DOI:10.1029/2006GL026369.
[23] VELICOGNA I, WAHR J. Measurements of Time-variable Gravity Show Mass Loss in Antarctica[J]. Science, 2006, 311:1754-1756,DOI:10.1126/science.1123785.
[24] CHEN J L, WILSON C R, TAPLEY B D, et al. Low Degree Gravitational Changes from GRACE: Validation and Interpretation[J]. Geophy. Res. Lett, 2004, 31, DOI: 10.1029/2004G L021670.
[25] CHAMBERS D P, WAHR J, NEREM R S. Preliminary Observations of Global Ocean Mass Variations with GRACE[J]. Geophysical Research Letters, 2004, 31,DOI:10.1029/2004GL020461.
[26] VELICOGNA I, WAHR J. Acceleration of Greenland Ice Mass Loss in Spring 2004[J]. Nature, 2006, 443:329-331, DOI:10.1038/nature05168.
[27] SWENSON S, WAHR J. Post-processing Removal of Correlated Errors in GRACE Data[J]. Geophyscial. Research Letters, 2006,33,DOI:10.1029/2005GL025285.
[28] ZHAN Jingang, WANG Yong, HAO Xiaoguang. Improved Method for Removal of Correlated Errors in GRACE Data[J]. Acta Geodaetica et Cartographica Sinica, 2011, 40(4):443-446.(詹金刚, 王勇, 郝晓光. GRACE时变重力位系数误差的改进去相关算法[J]. 测绘学报, 2011, 40(4):443-446.)
[29] ZHANG Z Z, CHAO B F. An Effective Filtering for GRACE Time-variable Gravity: Fan Filter[J]. Geophysical Research Letters,2009, 36,L17311, DOI: 10.1029/2009GL039459.
