本文采用吸湿性串联差分式电迁移粒径谱仪(Hygros-copicity Tandem Diferential Mobility Analyzer,H-TDMA)和气溶胶组分监测仪(S-611EG),对成都市2019年1—2月气溶胶粒子吸湿增长因子(GF)、气溶胶液态含水量(ALWC)、气溶胶谱分布(PNSD...本文采用吸湿性串联差分式电迁移粒径谱仪(Hygros-copicity Tandem Diferential Mobility Analyzer,H-TDMA)和气溶胶组分监测仪(S-611EG),对成都市2019年1—2月气溶胶粒子吸湿增长因子(GF)、气溶胶液态含水量(ALWC)、气溶胶谱分布(PNSD)、粒子化学组分进行观测,并结合气象要素分析了成都市大气气溶胶吸湿效应及其对能见度的影响。结果表明:(1)成都冬季40~200 nm的非吸湿模态粒子(GF_(NH))的吸湿增长因子随粒径增大而减小,强(弱)吸湿模态粒子的吸湿增长因子(GFMH,LH)均随粒径增大而增大,非(弱)吸湿性粒子比例(NF_(NH,LH))随粒径增大而减少。(2)成都冬季气溶胶液态含水量由爱根核模态和积聚模态粒子占主导,其中爱根核模态对ALWC贡献最大。相对湿度(RH)、细颗粒物(PM_(2.5))对ALWC的影响力依次降低,高PM_(2.5)且高RH是高ALWC的充分条件。(3)不利气象条件是成都此次雾霾过程的主要成因,低能见度在低RH时由PM_(2.5)积累所致,而气溶胶吸湿增长效应在高RH时主导能见度下降。展开更多
本研究利用2017—2023年陕西VLF/LF闪电定位系统地闪数据,基于GIS(Geographic Information System)核密度场模型,建立了基于强度权重的地闪核密度表面;应用热点探测模型对地闪密度热点进行提取和等级分类;分析了地闪核密度及其热点的分...本研究利用2017—2023年陕西VLF/LF闪电定位系统地闪数据,基于GIS(Geographic Information System)核密度场模型,建立了基于强度权重的地闪核密度表面;应用热点探测模型对地闪密度热点进行提取和等级分类;分析了地闪核密度及其热点的分布与地形地貌、植被覆盖等环境因素的关系。研究结果显示:①利用GIS核密度场模型和热点探测模型可以准确识别闪电活动密集区域,并深入揭示地闪空间分布特征。②陕西地闪活动存在明显的时空差异,地闪在夏季发生次数多强度大,春秋季次之,冬季最少;空间分布总体表现为南北高—中间低的空间格局。③核密度在海拔高度1 km以下与海拔高度正相关,在海拔高度1 km以上与海拔高度负相关;地形地貌、植被及两者交叉项均对核密度产生显著性差异影响。地形地貌影响的差异超过植被。④中海拔黄土梁峁和中海拔中起伏山地的草地和林区是大型及中大型热点的主要分布区。展开更多
Fine-scale structures can be observed in small field-of-view(FOV)auroral observations,but they are often overlooked because they appear only sporadically in all-sky observations.Such forms are of great interest becaus...Fine-scale structures can be observed in small field-of-view(FOV)auroral observations,but they are often overlooked because they appear only sporadically in all-sky observations.Such forms are of great interest because they may embody specific magnetosphere-ionosphere coupling processes,reveal localized energy deposition pathways,and provide new insights into cross-scale plasma dynamics and instabilities.However,their limited spatial extent,transient occurrence,and scarcity in wide-FOV observations make systematic investigation challenging.Traditional manual analysis struggles to capture these subtle structures within vast all-sky datasets,while automated detection faces severe data imbalance and morphological ambiguity.To address these challenges,we propose a synthetic-to-real progressive learning framework for cross-FOV retrieval of rare auroral forms.A Generative Adversarial Network(GAN)is employed to perform cross-FOV transformation between unpaired small-FOV images containing rare aurora forms and all-sky images(ASI)without such structures,thereby generating large numbers of synthetic ASI with rare auroral morphology.These synthetic samples are used to train an initial detection model,which subsequently undergoes iterative fine-tuning through feedback-guided learning:The model performs inference on new all-sky data,and the progressively accumulated real detections are incorporated into the training set.Experimental results demonstrate that the proposed method achieves over 92%detection accuracy on ASI,enabling high-precision retrieval of small-scale auroral structures across large-scale observations.This framework provides a scalable and effective approach to rediscovering rare auroral phenomena in continuous all-sky monitoring,offering new opportunities for exploring the fine-scale dynamics of the upper atmosphere.展开更多
We have examined an unusual rocket-triggered lightning flash during the summer campaign of the SHAndong Triggered Lightning Experiment(SHATLE)in 2018.High-speed video camera observations and three-dimensional(3D)light...We have examined an unusual rocket-triggered lightning flash during the summer campaign of the SHAndong Triggered Lightning Experiment(SHATLE)in 2018.High-speed video camera observations and three-dimensional(3D)lightning mapping show that the upward positive leader split into two branched channels(referred to as branch A&branch B,respectively)at a height of about 370 m,and then progressed into different charge regions of the thundercloud.Branch A initially developed upward before turning northwest from the trigger point;ten pronounced intermittent negative leaders were observed propagating downward along this branch channel,causing strong current pulses.Branch B propagated obliquely upward towards the northeast before continuing northward to a region of weak radar echo at 3 km altitude,resulting in a large-scale charge transfer of approximately–250 C(C=Coulomb)and generating a sustained,strong current exceeding 2 kA.Furthermore,downward dart leaders propagating along branch A connected to the active channel of branch B at the bifurcation point.This connection generated a surge of large current pulses(M-components)superimposed on the continuing current.Evidence from 3D lightning mapping and concurrent channel-base current measurements suggests that the 10th negative dart leader split during its downward propagation,with one branch propagating to ground,while the other entered into a positive charge reservoir.This initiated a positive charge transfer to ground via the existing channel,ultimately triggering the final stroke which exhibited a bi-polarity current pulse.展开更多
文摘本研究利用2017—2023年陕西VLF/LF闪电定位系统地闪数据,基于GIS(Geographic Information System)核密度场模型,建立了基于强度权重的地闪核密度表面;应用热点探测模型对地闪密度热点进行提取和等级分类;分析了地闪核密度及其热点的分布与地形地貌、植被覆盖等环境因素的关系。研究结果显示:①利用GIS核密度场模型和热点探测模型可以准确识别闪电活动密集区域,并深入揭示地闪空间分布特征。②陕西地闪活动存在明显的时空差异,地闪在夏季发生次数多强度大,春秋季次之,冬季最少;空间分布总体表现为南北高—中间低的空间格局。③核密度在海拔高度1 km以下与海拔高度正相关,在海拔高度1 km以上与海拔高度负相关;地形地貌、植被及两者交叉项均对核密度产生显著性差异影响。地形地貌影响的差异超过植被。④中海拔黄土梁峁和中海拔中起伏山地的草地和林区是大型及中大型热点的主要分布区。
基金supported by the National Natural Science Foundation of China(Grant no.41874173).
文摘Fine-scale structures can be observed in small field-of-view(FOV)auroral observations,but they are often overlooked because they appear only sporadically in all-sky observations.Such forms are of great interest because they may embody specific magnetosphere-ionosphere coupling processes,reveal localized energy deposition pathways,and provide new insights into cross-scale plasma dynamics and instabilities.However,their limited spatial extent,transient occurrence,and scarcity in wide-FOV observations make systematic investigation challenging.Traditional manual analysis struggles to capture these subtle structures within vast all-sky datasets,while automated detection faces severe data imbalance and morphological ambiguity.To address these challenges,we propose a synthetic-to-real progressive learning framework for cross-FOV retrieval of rare auroral forms.A Generative Adversarial Network(GAN)is employed to perform cross-FOV transformation between unpaired small-FOV images containing rare aurora forms and all-sky images(ASI)without such structures,thereby generating large numbers of synthetic ASI with rare auroral morphology.These synthetic samples are used to train an initial detection model,which subsequently undergoes iterative fine-tuning through feedback-guided learning:The model performs inference on new all-sky data,and the progressively accumulated real detections are incorporated into the training set.Experimental results demonstrate that the proposed method achieves over 92%detection accuracy on ASI,enabling high-precision retrieval of small-scale auroral structures across large-scale observations.This framework provides a scalable and effective approach to rediscovering rare auroral phenomena in continuous all-sky monitoring,offering new opportunities for exploring the fine-scale dynamics of the upper atmosphere.
基金supported by National Key R&D Program of China(2023YFC3007703,2017YFC1501501)the CAS Project of Stable Support for Youth Team in Basic Research Field(YSBR-018)+2 种基金National Natural Science Foundation of China(41875006,and U1938115)Youth Innovation Fund Project of the University(WK2080000172)the Chinese Meridian Project.
文摘We have examined an unusual rocket-triggered lightning flash during the summer campaign of the SHAndong Triggered Lightning Experiment(SHATLE)in 2018.High-speed video camera observations and three-dimensional(3D)lightning mapping show that the upward positive leader split into two branched channels(referred to as branch A&branch B,respectively)at a height of about 370 m,and then progressed into different charge regions of the thundercloud.Branch A initially developed upward before turning northwest from the trigger point;ten pronounced intermittent negative leaders were observed propagating downward along this branch channel,causing strong current pulses.Branch B propagated obliquely upward towards the northeast before continuing northward to a region of weak radar echo at 3 km altitude,resulting in a large-scale charge transfer of approximately–250 C(C=Coulomb)and generating a sustained,strong current exceeding 2 kA.Furthermore,downward dart leaders propagating along branch A connected to the active channel of branch B at the bifurcation point.This connection generated a surge of large current pulses(M-components)superimposed on the continuing current.Evidence from 3D lightning mapping and concurrent channel-base current measurements suggests that the 10th negative dart leader split during its downward propagation,with one branch propagating to ground,while the other entered into a positive charge reservoir.This initiated a positive charge transfer to ground via the existing channel,ultimately triggering the final stroke which exhibited a bi-polarity current pulse.
