Sanya VHF radar （18.4°N, 109.6°E, dip latitude 12.8°N） at Hainan Island is the first coherent backscatter radar for sounding low-latitude ionospheric irregularities in the mainland of China. In this p...Sanya VHF radar （18.4°N, 109.6°E, dip latitude 12.8°N） at Hainan Island is the first coherent backscatter radar for sounding low-latitude ionospheric irregularities in the mainland of China. In this paper, we present the first results of low-latitude iono- spheric E and F region irregularities using the radar data during the period from February 2009 to March 2010. The Doppler velocity of radar echoes from E region field aligned irregularities （FAIs） was about several tens of meters per second, while the Doppler spectral width was appreciably larger than the velocity, and could reach one hundred meters per second, indicating that the observed E region FAls belonged to type 2 irregularities. The observations of range time intensity （RTI） maps of FAIs showed that E region irregularities most often occurred at night within the altitude range 85-115 kin, and were rarely observed at afternoon hours. The percentage occurrence of E region FAIs maximized during spring months （Feb.-May） with a peak value over 80%. The heights at which the strongest echo related FAIs occurred were mainly around 100 kin, lower than h＇Es and the difference is mostly 10-20 km. December solstice seemed to be the minimum period of occurrence when the FA! ech- oes were commonly detected at a narrow altitude range 90-100 km. Moreover, simultaneous radar and GPS observations dur- ing spread F events in the pre-midnight hours of solar minimum revealed that significant GPS L band scintillations coincided with the appearance of F region plasma plume structures, which extended up to 450 km in altitude.展开更多
Many observations have revealed the complex motions of the atmosphere because of the rapid developement of experiment technique. However, as compared with numerical stimulations of atmospheric dynamic system, little i...Many observations have revealed the complex motions of the atmosphere because of the rapid developement of experiment technique. However, as compared with numerical stimulations of atmospheric dynamic system, little is known about the complexity occurring in the real atmosphere. The chaotic motion can usually be described by 3 characteristic quantities for the dissipative motion of the atmosphere: dimension, Lyapunov exponent展开更多
【目的】利用子午工程甚高频(very high frequency,VHF)相干散射雷达观测数据,基于深度学习技术对低纬F区电离层3m尺度不规则体进行识别与特征提取。【方法】本文基于CSPDarknet神经网络技术构建了电离层不规则体事件智能识别模型,并基...【目的】利用子午工程甚高频(very high frequency,VHF)相干散射雷达观测数据,基于深度学习技术对低纬F区电离层3m尺度不规则体进行识别与特征提取。【方法】本文基于CSPDarknet神经网络技术构建了电离层不规则体事件智能识别模型,并基于预训练好的CSPDarknet为骨干网络以及Yolo目标检测算法,构建了电离层不规则体事件定位模型。【结果】所构建不规则体识别模型能自动从整天甚高频相关散射雷达观测数据当中挑选出低纬电离层不规则体,并根据不规则体定位模型提取出不规则体的高度和持续时间。实验结果表明,不规则体识别模型的F1得分达到了85.89%,比EfficientNet模型的F1得分高5.68%;不规则体定位模型的平均精度指标mAP可以达到87.22%,比Yolov5s模型的mAP高4.32%。【局限】模型训练过程中主要利用了海南富克站单台站的观测数据,为提升模型的泛化性能需进一步引入更多台站观测数据。【结论】本文基于深度学习技术首次提出了一套电离层不规则体事件的智能识别与定位方案,极大改善了传统基于阈值法识别不规则体效率低下且依赖专家的问题,提升了电离层不规则体的研究效率。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41074113, 40904038, 40774091, 41174136)Chinese Academy of Sciences (Grant No. KZCX2-YW-Y10)
文摘Sanya VHF radar （18.4°N, 109.6°E, dip latitude 12.8°N） at Hainan Island is the first coherent backscatter radar for sounding low-latitude ionospheric irregularities in the mainland of China. In this paper, we present the first results of low-latitude iono- spheric E and F region irregularities using the radar data during the period from February 2009 to March 2010. The Doppler velocity of radar echoes from E region field aligned irregularities （FAIs） was about several tens of meters per second, while the Doppler spectral width was appreciably larger than the velocity, and could reach one hundred meters per second, indicating that the observed E region FAls belonged to type 2 irregularities. The observations of range time intensity （RTI） maps of FAIs showed that E region irregularities most often occurred at night within the altitude range 85-115 kin, and were rarely observed at afternoon hours. The percentage occurrence of E region FAIs maximized during spring months （Feb.-May） with a peak value over 80%. The heights at which the strongest echo related FAIs occurred were mainly around 100 kin, lower than h＇Es and the difference is mostly 10-20 km. December solstice seemed to be the minimum period of occurrence when the FA! ech- oes were commonly detected at a narrow altitude range 90-100 km. Moreover, simultaneous radar and GPS observations dur- ing spread F events in the pre-midnight hours of solar minimum revealed that significant GPS L band scintillations coincided with the appearance of F region plasma plume structures, which extended up to 450 km in altitude.
文摘Many observations have revealed the complex motions of the atmosphere because of the rapid developement of experiment technique. However, as compared with numerical stimulations of atmospheric dynamic system, little is known about the complexity occurring in the real atmosphere. The chaotic motion can usually be described by 3 characteristic quantities for the dissipative motion of the atmosphere: dimension, Lyapunov exponent
文摘【目的】利用子午工程甚高频(very high frequency,VHF)相干散射雷达观测数据,基于深度学习技术对低纬F区电离层3m尺度不规则体进行识别与特征提取。【方法】本文基于CSPDarknet神经网络技术构建了电离层不规则体事件智能识别模型,并基于预训练好的CSPDarknet为骨干网络以及Yolo目标检测算法,构建了电离层不规则体事件定位模型。【结果】所构建不规则体识别模型能自动从整天甚高频相关散射雷达观测数据当中挑选出低纬电离层不规则体,并根据不规则体定位模型提取出不规则体的高度和持续时间。实验结果表明,不规则体识别模型的F1得分达到了85.89%,比EfficientNet模型的F1得分高5.68%;不规则体定位模型的平均精度指标mAP可以达到87.22%,比Yolov5s模型的mAP高4.32%。【局限】模型训练过程中主要利用了海南富克站单台站的观测数据,为提升模型的泛化性能需进一步引入更多台站观测数据。【结论】本文基于深度学习技术首次提出了一套电离层不规则体事件的智能识别与定位方案,极大改善了传统基于阈值法识别不规则体效率低下且依赖专家的问题,提升了电离层不规则体的研究效率。
