延迟是全球卫星导航定位中重要的误差源之一,提高电离层TEC建模和预报精度对改善卫星导航定位精度至关重要.本文构建了以太阳辐射通量指数F_(10.7)、地磁活动指数Dst、地理坐标和中国科学院(Chinese Academy of Sciences,CAS)GIM数据为...延迟是全球卫星导航定位中重要的误差源之一,提高电离层TEC建模和预报精度对改善卫星导航定位精度至关重要.本文构建了以太阳辐射通量指数F_(10.7)、地磁活动指数Dst、地理坐标和中国科学院(Chinese Academy of Sciences,CAS)GIM数据为输入参数的NeuralProphet神经网络模型(NP模型),实现在2015年3月特大磁暴期中国区域电离层TEC短期预报.为验证NP模型的预报精度,本文同时构建了长短期记忆神经网络(Long Short-term Memory Neural Network,LSTM)模型进行对比分析.结果统计分析表明,NP模型在磁暴期(2015年DOY076-078)TEC预报值RMSE和RD分别为0.83 TECU和3.13%,绝对和相对精度较LSTM模型分别提高1.49 TECU和10.25%;且NP模型RMSE优于1.5 TECU的比例达97.24%,远高于LSTM模型.NP模型预报值与CAS具有较好一致性和无偏性,偏差均值仅为-0.01 TECU,而LSTM模型预报值的均值偏大,偏差均值为1.49 TECU.从低纬到中纬度的三个纬度带内,NP模型RMSE分别为1.12、0.83和0.44 TECU,精度比LSTM模型提高1.94、1.56和1.23 TECU.整体上,在磁暴期NP模型预报性能明显优于LSTM模型,能够精细描述中国区域电离层TEC时空变化.展开更多
电离层TEC(Total Electron Content)扰动与多种扰动源相关联.2009年6至7月期间存在地震和日全食的扰动源.利用广州地区GPS监测网在2009年6至7月连续监测到的TEC数据,通过采用前15天数据的滑动窗口对数据进行处理,从时间序列和空间分布...电离层TEC(Total Electron Content)扰动与多种扰动源相关联.2009年6至7月期间存在地震和日全食的扰动源.利用广州地区GPS监测网在2009年6至7月连续监测到的TEC数据,通过采用前15天数据的滑动窗口对数据进行处理,从时间序列和空间分布两方面分析了华南地区电离层TEC扰动特征.结果显示,2009年6至7月华南地区电离层TEC扰动和该时期发生的地震以及日全食事件可能有关联;2009年7月多个地震发生引起的电离层扰动特征为,震前出现的是正异常,发震当天或震后有可能是正异常,也有可能是负异常;7月22日日全食当天TEC扰动为正异常,推测该正异常是地磁活动、地震活动及日全食综合效应的结果.展开更多
半参数球谐函数(Semiparametric Spherical Harmonic,Semi-SH)模型能减少电离层预报模型误差以及残余周期带来的系统误差.但是半参数球谐函数模型中窗宽参数的选取会带来一定的估计偏差,本文利用长短期记忆神经网络(Long-Short Term Mem...半参数球谐函数(Semiparametric Spherical Harmonic,Semi-SH)模型能减少电离层预报模型误差以及残余周期带来的系统误差.但是半参数球谐函数模型中窗宽参数的选取会带来一定的估计偏差,本文利用长短期记忆神经网络(Long-Short Term Memory Networks,LSTM)在非平稳性时间序列预报中的良好适应性,提出了一种联合Semi-SH与LSTM(Semi-SH-LSTM)的全球电离层TEC短期组合预报模型,适用于1—5天的短期预报.Semi-SH-LSTM模型通过预报球谐函数系数解算全球电离层TEC,利用二次多项式和半参数核估计方法分别拟合球谐系数趋势项和周期项,最后基于LSTM对拟合残差进行补偿预报.本文利用欧洲定轨中心(Center for Orbit Determination in Europe,CODE)球谐函数系数产品,采用单天预报和多天预报两种实验方案验证Semi-SH-LSTM模型的有效性.实验结果表明,相比于Semi-SH模型和综合半参数与自回归模型,Semi-SH-LSTM模型的单天全球TEC预报残差RMS值分别提升了12.6%和13.1%;误差小于1 TECU占比分别提升了4.9%、4.6%.基于Semi-SH-LSTM模型的多天全球TEC预报残差RMS值分别提升了10.5%和8.5%,误差小于1 TECU占比提升了3.9%和3.2%.同时,半参数LSTM组合预报模型每预报一天耗时约在2 h以内.展开更多
Total Electron Content(TEC)and electron density enhancement were observed on the day before 17 March 2015 great storm in the China Region.Observations from ground-and space-based instruments are used to investigate th...Total Electron Content(TEC)and electron density enhancement were observed on the day before 17 March 2015 great storm in the China Region.Observations from ground-and space-based instruments are used to investigate the temporal and spatial evolution of the pre-storm enhancement.TEC enhancement was observed from 24°N to 30°N after 10:00 UT at 105°E,110°E and 115°E longitudes on March 16.The maximum magnitude of TEC enhancement was more than 10 TECU and the maximal relative TEC enhancement exceeded 30%.Compared with geomagnetic quiet days,the electron density of Equatorial Ionization Anomaly(EIA)northern peak from Swarm A/C satellites on March 16 was larger and at higher latitudes.NmF2 enhanced during 11:30—21:00 UT at Shaoyang Station and increased by 200%at~16:00 UT.However,TEC and electron density enhancement were not accompanied by a significant change of hmF2.Most research has excluded some potential mechanisms as the main driving factors for storm-time density enhancements by establishing observational constraints.In this paper,we observed pre-storm enhancement in electron density at different altitudes and Equatorial Electrojet(EEJ)strength results derived from ground magnetometers observations suggest an enhanced eastward electric field from the E region probably played a significant role in this event.展开更多
The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from ...The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from GPS observations at stations of Shenzhen and Guangzhou from 2011 to 2012.This study reported that the ratio of simultaneous occurrences of TEC depletions with strong scintillations was higher than that of TEC depletions with weak scintillations in vernal and autumnal equinoxes of 2011 over South China.The number of the periodic structures of TEC with depletion contained was greater than that with no depletion contained corresponding to strong scintillations.The structure of the slab of plasma irregularities could be responsible for the simultaneous occurrences of TEC depletion with strong scintillations and ROTI.Before and during the occurrences of strong scintillation,there was Large-Scale Wave Structure(LSWS) which provided the seed ionization perturbation to trigger ESF irregularities and contributed to the periodic structure of TEC.展开更多
2023年2月6日土耳其连续2次7.8级地震是一次显著的地质构造运动,也是一个特别典型的科学实验场景。当前各类观测数据较为丰富,为全球学者验证自己的猜想和进行模型实验提供了绝佳的机会。本文利用自行研究的热红外年均线差值振幅增强比...2023年2月6日土耳其连续2次7.8级地震是一次显著的地质构造运动,也是一个特别典型的科学实验场景。当前各类观测数据较为丰富,为全球学者验证自己的猜想和进行模型实验提供了绝佳的机会。本文利用自行研究的热红外年均线差值振幅增强比法和TEC(Total Electron Content,电离层总电子含量)微观异常事件滑动年均线法研究发现,分别于2022年4月底至5月上旬、8月,在震中区域东西两侧曾出现高强度热红外异常;震前约1个月,震中东西两侧及北部区域同步热红外活跃性显著增强,尤其是北部区域其年线差值振幅增强比值在2023年1月31日创新高,是2018年以来最高记录,且为震前4年平均水平的2.5倍。TEC微观异常事件滑动年均线法研究显示,震中及附近区域TEC微观异常事件年线值从2021年开始快速下降,震前均值创历史最低水平,其年均值降至2000年以来高点的25%。热红外及TEC 2种异常在时间、空间上存在高度重叠,且地震发生在以上2种异常区域内,说明2种异常与本次地震系列可能存在密切联系。展开更多
文摘电离层TEC(Total Electron Content)扰动与多种扰动源相关联.2009年6至7月期间存在地震和日全食的扰动源.利用广州地区GPS监测网在2009年6至7月连续监测到的TEC数据,通过采用前15天数据的滑动窗口对数据进行处理,从时间序列和空间分布两方面分析了华南地区电离层TEC扰动特征.结果显示,2009年6至7月华南地区电离层TEC扰动和该时期发生的地震以及日全食事件可能有关联;2009年7月多个地震发生引起的电离层扰动特征为,震前出现的是正异常,发震当天或震后有可能是正异常,也有可能是负异常;7月22日日全食当天TEC扰动为正异常,推测该正异常是地磁活动、地震活动及日全食综合效应的结果.
文摘半参数球谐函数(Semiparametric Spherical Harmonic,Semi-SH)模型能减少电离层预报模型误差以及残余周期带来的系统误差.但是半参数球谐函数模型中窗宽参数的选取会带来一定的估计偏差,本文利用长短期记忆神经网络(Long-Short Term Memory Networks,LSTM)在非平稳性时间序列预报中的良好适应性,提出了一种联合Semi-SH与LSTM(Semi-SH-LSTM)的全球电离层TEC短期组合预报模型,适用于1—5天的短期预报.Semi-SH-LSTM模型通过预报球谐函数系数解算全球电离层TEC,利用二次多项式和半参数核估计方法分别拟合球谐系数趋势项和周期项,最后基于LSTM对拟合残差进行补偿预报.本文利用欧洲定轨中心(Center for Orbit Determination in Europe,CODE)球谐函数系数产品,采用单天预报和多天预报两种实验方案验证Semi-SH-LSTM模型的有效性.实验结果表明,相比于Semi-SH模型和综合半参数与自回归模型,Semi-SH-LSTM模型的单天全球TEC预报残差RMS值分别提升了12.6%和13.1%;误差小于1 TECU占比分别提升了4.9%、4.6%.基于Semi-SH-LSTM模型的多天全球TEC预报残差RMS值分别提升了10.5%和8.5%,误差小于1 TECU占比提升了3.9%和3.2%.同时,半参数LSTM组合预报模型每预报一天耗时约在2 h以内.
基金Fundamental Research Funds for the Central Universities(No.B230201012)National Natural Science Foundation of China(No.42104009)China Postdoctoral Science Foundation(No.2022M720988)。
文摘Total Electron Content(TEC)and electron density enhancement were observed on the day before 17 March 2015 great storm in the China Region.Observations from ground-and space-based instruments are used to investigate the temporal and spatial evolution of the pre-storm enhancement.TEC enhancement was observed from 24°N to 30°N after 10:00 UT at 105°E,110°E and 115°E longitudes on March 16.The maximum magnitude of TEC enhancement was more than 10 TECU and the maximal relative TEC enhancement exceeded 30%.Compared with geomagnetic quiet days,the electron density of Equatorial Ionization Anomaly(EIA)northern peak from Swarm A/C satellites on March 16 was larger and at higher latitudes.NmF2 enhanced during 11:30—21:00 UT at Shaoyang Station and increased by 200%at~16:00 UT.However,TEC and electron density enhancement were not accompanied by a significant change of hmF2.Most research has excluded some potential mechanisms as the main driving factors for storm-time density enhancements by establishing observational constraints.In this paper,we observed pre-storm enhancement in electron density at different altitudes and Equatorial Electrojet(EEJ)strength results derived from ground magnetometers observations suggest an enhanced eastward electric field from the E region probably played a significant role in this event.
基金Supported by the National Natural Science Young Foundation of China(41704168)。
文摘The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from GPS observations at stations of Shenzhen and Guangzhou from 2011 to 2012.This study reported that the ratio of simultaneous occurrences of TEC depletions with strong scintillations was higher than that of TEC depletions with weak scintillations in vernal and autumnal equinoxes of 2011 over South China.The number of the periodic structures of TEC with depletion contained was greater than that with no depletion contained corresponding to strong scintillations.The structure of the slab of plasma irregularities could be responsible for the simultaneous occurrences of TEC depletion with strong scintillations and ROTI.Before and during the occurrences of strong scintillation,there was Large-Scale Wave Structure(LSWS) which provided the seed ionization perturbation to trigger ESF irregularities and contributed to the periodic structure of TEC.
文摘2023年2月6日土耳其连续2次7.8级地震是一次显著的地质构造运动,也是一个特别典型的科学实验场景。当前各类观测数据较为丰富,为全球学者验证自己的猜想和进行模型实验提供了绝佳的机会。本文利用自行研究的热红外年均线差值振幅增强比法和TEC(Total Electron Content,电离层总电子含量)微观异常事件滑动年均线法研究发现,分别于2022年4月底至5月上旬、8月,在震中区域东西两侧曾出现高强度热红外异常;震前约1个月,震中东西两侧及北部区域同步热红外活跃性显著增强,尤其是北部区域其年线差值振幅增强比值在2023年1月31日创新高,是2018年以来最高记录,且为震前4年平均水平的2.5倍。TEC微观异常事件滑动年均线法研究显示,震中及附近区域TEC微观异常事件年线值从2021年开始快速下降,震前均值创历史最低水平,其年均值降至2000年以来高点的25%。热红外及TEC 2种异常在时间、空间上存在高度重叠,且地震发生在以上2种异常区域内,说明2种异常与本次地震系列可能存在密切联系。
