一般通过在国界外围均匀添加一定数量的IGRF点以改善区域地磁场模型的边界效应.而最新的地磁场综合模型(Comprehensive Model 4,CM4)可以计算1960～2002年内全球任意区域的地核场、地壳场、磁层场及其感应场、电离层场及其感应场,其内...一般通过在国界外围均匀添加一定数量的IGRF点以改善区域地磁场模型的边界效应.而最新的地磁场综合模型(Comprehensive Model 4,CM4)可以计算1960～2002年内全球任意区域的地核场、地壳场、磁层场及其感应场、电离层场及其感应场,其内源场比IGRF更适合作为边界补充点以提高模型精度.本文对CM4和IGRF10的地核场网格图进行了比较,并以Taylor多项式模型为例,通过将34个CM4的内源场数据点和34个IGRF10的数值点分别作为边界补充点代入计算出网格值,并将其相减以分析差异.结果显示:各分量在国内大部分区域差异很小,几乎都为0值,在境外区域除了北向分量(X),其余分量均是正值,说明结合IGRF10建立的模型在国界外区域的数值偏小.展开更多
The selection of the truncation level （TL） and the control of boundary effect （BE） are critical in regional geomagnetic field models that are based on data fitting. We combine Taylor and Legendre polynomials to mo...The selection of the truncation level （TL） and the control of boundary effect （BE） are critical in regional geomagnetic field models that are based on data fitting. We combine Taylor and Legendre polynomials to model geomagnetic data over China's Mainland for years 1960, 1970, 1990, and 2000. To tackle the TL and BE problems, we first determine the range of TL by calculating the root-mean-square error （RMSE） of the models. Next, we determine the optimum TL using the Akaike information criterion （AIC） and the normalized root- mean-square error （NRMSE）. We use the regional anomaly addition （RAA） and the uniform addition （UA） method to add supplementary point outside the national boundary, and find that the intensities of extreme points gradually decrease and stabilize. The UA method better controls BEs over China, whereas the RAA method does a better job at smaller scales. In summary, we rely on a three-step method to determine the optimum TL and propose criteria to determine the optimum number of supplementary points.展开更多
文摘一般通过在国界外围均匀添加一定数量的IGRF点以改善区域地磁场模型的边界效应.而最新的地磁场综合模型(Comprehensive Model 4,CM4)可以计算1960～2002年内全球任意区域的地核场、地壳场、磁层场及其感应场、电离层场及其感应场,其内源场比IGRF更适合作为边界补充点以提高模型精度.本文对CM4和IGRF10的地核场网格图进行了比较,并以Taylor多项式模型为例,通过将34个CM4的内源场数据点和34个IGRF10的数值点分别作为边界补充点代入计算出网格值,并将其相减以分析差异.结果显示:各分量在国内大部分区域差异很小,几乎都为0值,在境外区域除了北向分量(X),其余分量均是正值,说明结合IGRF10建立的模型在国界外区域的数值偏小.
基金supported by the National Natural Science Foundation of China(Grant Nos.41404053 and 41174165)Special Project for Meteo-Scientific Research in the Public Interest(Grant No.GYHY201306073)Natural Science Foundation of Higher Education Institutions of Jiangsu Province,China(Grant No.14KJB170012)
文摘The selection of the truncation level （TL） and the control of boundary effect （BE） are critical in regional geomagnetic field models that are based on data fitting. We combine Taylor and Legendre polynomials to model geomagnetic data over China's Mainland for years 1960, 1970, 1990, and 2000. To tackle the TL and BE problems, we first determine the range of TL by calculating the root-mean-square error （RMSE） of the models. Next, we determine the optimum TL using the Akaike information criterion （AIC） and the normalized root- mean-square error （NRMSE）. We use the regional anomaly addition （RAA） and the uniform addition （UA） method to add supplementary point outside the national boundary, and find that the intensities of extreme points gradually decrease and stabilize. The UA method better controls BEs over China, whereas the RAA method does a better job at smaller scales. In summary, we rely on a three-step method to determine the optimum TL and propose criteria to determine the optimum number of supplementary points.
基金Supported by the National Natural Science Foundation of China(Grant No:4140405341174165)+1 种基金National Natural Science Foundation of China(Grant No.14KJB170012)Special Project for Meteo-scientific Research in the Public Interest(Grant No:GYHY201306073)
