Medium-Long Term Forecasting Method for Earth Rotation Parameters Considering Effective Angular Momentum Information
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摘要:
地球自转参数(Earth rotation parameters, ERP)的预报精度一直是卫星自主导航和深空探测等用户关注的焦点。为了进一步提升用户的满意度,首先将激发域的有效角动量(effective angular momentum, EAM)的拟合残差序列卷积到大地测量观测域,并添加经验调节因子,构造出新的EAM拟合残差序列;然后将ERP和新的EAM拟合残差序列做减法,获得差异序列;最后联合差异序列和新的EAM残差序列的预报值,推出目标ERP序列的预报值。使用由ERP数据驱动的最小二乘外推和自回归(the least square extrapolation and autoregressive,LS+AR)模型,从2012年初到2021年初的预报实验结果显示,在1~ 365 d的预报窗口上,X方向和Y方向的调节因子均为0.7时,分别较传统方法平均提高31.86%和21.00%;日长变化的调节因子为1时,较传统方法平均提升15%。这用数值预报的方式验证了极移短时间尺度的约70%高频变化由EAM激发这一已有结论,并为ERP预报研究提供了参考。
Abstract:ObjectivesThe prediction accuracy of Earth rotation parameters (ERP), as one of the hot spots in geodetic research, has been attracting attention from users such as autonomous satellite navigation and deep space exploration. In order to further satisfy the users' requirements, we combine the new effective angular momentum (EAM) data for the ERP prediction study.
MethodsThe EAM fitted residual series in the excitation domain is first transferred to the geodetic observation domain, and an empirical adjustment factor is added to construct a new EAM fitted residual series. Then the fitted residual series of ERP and the fitted residual series of the new EAM are subtracted to obtain the difference series. Using the least square extrapolation and autoregressive (LS+AR) models driven by ERP data, prediction experiments are performed for the difference series and the new EAM residual series, respectively, and finally predictions for the target ERP series are jointly introduced.
ResultsBased on experiments from the beginning of 2012 to the beginning of 2021, it is shown that an overall better result can be obtained for the adjustment factor of 0.7 in both the X-direction and Y-direction at a prediction horizons of 1-365 days, with an average improvement of 31.86% and 21.00% over the traditional method, respectively. The average improvement over the traditional method is 15% when the adjustment factor of length of day is 1.
ConclusionsThis verifies the existing conclusion that about 70% of the high-frequency changes in the short time scale of polar motion are stimulated by EAM by means of numerical prediction, and provides a reference for ERP prediction research.
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感谢IERS提供ERP数据,感谢GFZ地球系统建模小组提供EAM数据。
http://ch.whu.edu.cn/cn/article/doi/10.13203/j.whugis20220246
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表 1 本文的预报方案
Table 1 Prediction Schemes of This Paper
预报方案 调节因子 输入数据的长度 方案1 1 极移是3~10 aLOD是18 a 方案2 0.2 方案3 0.4 方案4 0.6 方案5 0.7 方案6 0.8 方案7 0.9 传统方法 0 IERS公报A 表 2 本文方法、传统方法和IERS 公报A的MAE
Table 2 MAE Values of the Proposed Method, Traditional Method and Bulletin A
ERP 方案 不同时间窗口的MAE 1 d 30 d 60 d 90 d 120 d 150 d 180 d 240 d 300 d 365 d X/m(″) 方案1 (5 a) 0.183 7.118 12.317 15.692 17.583 18.237 18.016 19.516 22.094 22.531 方案5 (5 a) 0.181 7.033 12.060 15.295 16.680 17.019 16.848 18.876 20.834 20.947 方案6 (5 a) 0.181 7.005 12.055 15.359 16.906 17.339 17.159 18.954 21.217 21.306 方案7 (5 a) 0.182 7.042 12.117 15.452 17.139 17.737 17.699 19.391 21.733 21.891 传统方法 0.178 8.224 16.606 23.498 28.133 30.050 29.719 27.919 28.965 31.222 IERS公报A 0.270 6.811 11.472 14.405 16.388 17.833 18.726 21.060 22.449 23.050 /% -1.69 14.48 27.38 34.91 40.71 43.36 43.31 32.39 28.07 32.91 Y/m(″) 方案1 (4 a) 0.165 7.320 16.447 24.218 28.963 30.733 30.630 29.936 30.128 31.023 方案2 (4 a) 0.150 5.811 11.393 15.326 17.470 18.345 18.835 19.043 19.299 21.387 方案1 (5 a) 0.165 7.230 16.404 24.999 30.772 33.449 33.807 33.275 34.495 35.031 方案5 (5 a) 0.144 5.301 10.296 14.216 16.713 18.778 20.067 21.263 21.362 24.049 方案6 (5 a) 0.144 5.360 10.500 14.546 16.883 18.979 20.298 21.462 21.813 24.769 方案7 (5 a) 0.146 5.407 10.713 14.906 17.051 18.853 20.229 21.580 22.464 25.337 传统方法 0.148 5.926 12.560 19.313 24.405 27.214 27.725 24.789 25.874 28.685 IERS公报A 0.198 4.306 7.719 11.871 16.645 20.769 23.676 25.825 25.613 25.041 /% 2.70 10.55 18.03 26.39 31.52 31.00 27.62 14.22 17.44 16.16 LOD/ms 方案1 (18 a) 0.019 0.154 0.168 0.178 0.183 0.196 0.212 0.231 0.260 0.277 传统方法 0.029 0.166 0.192 0.213 0.224 0.242 0.256 0.268 0.285 0.293 /% 32.14 7.23 12.50 16.43 18.30 19.01 17.19 13.43 8.42 5.46 -
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