Strong flares and/or coronal mass ejections(CMEs) could bring us disastrous space weather,destroy crucial technology in space,and cause a large-scale blackout during some extreme cases.They frequently cause geomagneti...Strong flares and/or coronal mass ejections(CMEs) could bring us disastrous space weather,destroy crucial technology in space,and cause a large-scale blackout during some extreme cases.They frequently cause geomagnetic storms,which is a sudden disturbance of the Earth's magnetosphere.It is well accepted that CMEs play a dominant role in causing geomagnetic storms by a direct impact,but it is still not very clear regarding their association with solar flares.The association would be helpful for forecasting geomagnetic storms directly from flares,which are much easier to observe.The Macao Science Satellite-1(MSS-1) mission,with the scientific aim of studying the origin and evolution of the geomagnetic field,is able to accurately measure the vector geomagnetic field.Besides,it measures rapid spectral evolution of the solar X-ray irradiance of solar flares.In this study,we analyzed measurements by MSS-1 during a series of X-class flares in October of 2024,and saw the relationship between the flares and the associated geomagnetic storms.The observations support that the major geomagnetic storms tend to be associated with flares' duration in addition to flare class.We also find that long duration ones have radiated more energy in the extreme ultraviolet waveband.Being equally important,our results show that the magnetic fields measured by MSS-1,especially its external(e_(1)^(0)) coefficient,can well be used for monitoring the geomagnetic disturbance.展开更多
This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic li...This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic linkages with Northeast China cold vortices(NCCVs)of tornadic storms under different convective modes.Results reveal that discrete storms account for 70%of events,with clustered cells(CC)being the most frequent mode,while significant tornadoes(EF2+)are primarily associated with isolated cells(IC)and broken lines(BL).The storm mode distribution in northeastern China resembles that of the central United States but with a higher proportion of CC and lower IC.In contrast,southern China exhibits a higher frequency of quasi-linear(QL)modes(>50%),similar to European patterns.Although no single parameter clearly differentiates between all tornado modes,distinct morphological characteristics emerge through specific parameter combinations:NL modes are characterized by high 0-1 km storm-relative helicity(SRH1)and humidity but low 0-6 km shear(SR6),whereas IC modes display contrasting features with low SRH1 and high CAPE.Notably,83%of tornadoes are associated with NCCVs,preferentially forming in southeastern/southwestern quadrants.Strong tornadoes favor southeastern quadrants,while NCCV intensity correlates with tornadic distance from vortex centers.Three characteristic synoptic configurations emerge:(T1)strong deep vortices with vertically aligned cold troughs,generating southeast-dominant tornado clusters characterized by a high proportion of BL and QL modes;(T2)weaker vortices featuring sub-synoptic troughs,with southern-distributed events dominated by a predominance of the CC mode;(T3)transverse-trough systems exhibiting CAPE-SRH decoupling and reduced tornadic activity.This study enhances our understanding of tornadoes in northeastern China,informing future research on formation mechanisms,prediction methods,and disaster prevention strategies.展开更多
The Hong Kong Observatory(HKO)installed an X-band dual-polarization Phased Array Weather Radar(PAWR)at its wind profiler station at Sha Lo Wan(SLW)in 2021 to monitor high-impact weather in Hong Kong.The PAWR could com...The Hong Kong Observatory(HKO)installed an X-band dual-polarization Phased Array Weather Radar(PAWR)at its wind profiler station at Sha Lo Wan(SLW)in 2021 to monitor high-impact weather in Hong Kong.The PAWR could complete a volume scan in one minute with a spatial resolution of 30 meters.Dual polarimetric variables from the SLW PAWR,including differential reflectivity(ZDR),specific differential phase(KDP),and hydro-classification(HCL)products,were used to diagnose the vertical motion and lightning characteristics of mesoscale convective storms(MCS).Through variational data assimilation,three-dimensional(3-D)wind fields were constructed to validate the SLW PAWR observations.Two MCS events that occurred on 18 September 2022 and 17 June 2023 are central to this study.The findings include(1)negative ZDR serves as a good indicator of the occurrence of intense downdrafts associated with an MCS,a premise further supported by the 3-D wind field analysis results,(2)negative KDP suggested the formation of vertically aligned ice crystals which facilitated cloud electrification,and(3)HCL products indicated the presence of mixed ice crystals and graupel above the 0℃melting layer which promoted active cloud-to-cloud and cloud-to-ground lightning strokes.These results show that the SLW PAWR provides essential observations,which,when coupled with 3-D wind field analysis,can aid in enhancing the understanding of the dynamics and electrification processes within an MCS.展开更多
Control signaling is mandatory for the operation and management of all types of communication networks,including the Third Generation Partnership Project(3GPP)mobile broadband networks.However,they consume important a...Control signaling is mandatory for the operation and management of all types of communication networks,including the Third Generation Partnership Project(3GPP)mobile broadband networks.However,they consume important and scarce network resources such as bandwidth and processing power.There have been several reports of these control signaling turning into signaling storms halting network operations and causing the respective Telecom companies big financial losses.This paper draws its motivation from such real network disaster incidents attributed to signaling storms.In this paper,we present a thorough survey of the causes,of the signaling storm problems in 3GPP-based mobile broadband networks and discuss in detail their possible solutions and countermeasures.We provide relevant analytical models to help quantify the effect of the potential causes and benefits of their corresponding solutions.Another important contribution of this paper is the comparison of the possible causes and solutions/countermeasures,concerning their effect on several important network aspects such as architecture,additional signaling,fidelity,etc.,in the form of a table.This paper presents an update and an extension of our earlier conference publication.To our knowledge,no similar survey study exists on the subject.展开更多
Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked t...Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked to equatorial plasma bubbles(EPBs),regions of depleted plasma density that form after sunset.Ionospheric scintillation typically occurs from post-sunset hours until midnight.Post-sunset EPBs can be enhanced or suppressed during geomagnetic storms,depending on local sunset timing and how it relates to the storm's main or recovery phases.This study analyzes ionospheric scintillation in Indonesia,located at low geomagnetic and geographic latitudes,during geomagnetic events from 2003 to 2024.Using the S4 index,scintillation was examined with data from seven observation stations during geomagnetic storm events.Geomagnetic activity was evaluated using Dst,SYM-H,and AE indices,employing Superposed Epoch Analysis(SEA)to assess scintillation occurrence linked to minimum SYM-H,defined as epoch 0 to represent the storm peak or the onset of recovery phase in each event.The analysis categorized geomagnetic storms into weak-moderate(–100 nT<min.Dst≤–30 nT)and strong(min.Dst≤–100 nT),and examined their dependence on the local time of minimum SYM-H.Results indicate that scintillation first appears~6 hours after epoch 0 in weak-moderate geomagnetic storms,and~12 hours after epoch 0 in strong geomagnetic storms.The average AE index returns to its baseline value(quiet condition)~6 and~12 hours after epoch 0 for weak-moderate and strong geomagnetic storms,respectively.Further analysis based on the classification of the local time of epoch 0 shows that scintillation occurrence is not observed in post-sunset hours when epoch 0 falls between 16:00 and 19:00 LT for weak-moderate geomagnetic storms.In strong geomagnetic storms,scintillation occurrence during post-sunset hours is absent when epoch 0 is between 10:00 and 19:00 LT.Notably,when the minimum SYM-H(epoch 0)nearly coincides with local sunset,scintillation activity occurs around sunset in both weak-moderate and strong geomagnetic storms.Furthermore,when epoch 0 falls within midnight until early morning,scintillation can be generated in the post-sunset hours before epoch 0.Still,post-midnight scintillation is not observed in the equatorial region during the recovery phase of either weak-moderate and strong storm events.Our findings show that when sunset falls before or coincide with epoch 0,the likelihood of post-sunset EPB and scintillation increases,due to the prompt-penetration electric field(PPEF)in the main phase of storm.The disturbance dynamo electric field(DDEF)in the recovery phase driven by equatorward winds from auroral Joule heating operates for at least 6-and 12-hours post-epoch 0 in the cases of weak-moderate and strong geomagnetic storms,respectively.When the local sunset falls within these operational DDEF periods,post-sunset EPBs will likely be suppressed,inhibiting ionospheric scintillation during post-sunset hours.Finally,this study provides essential information for developing more accurate ionospheric scintillation prediction models in space weather services in equatorial regions.展开更多
Proper knowledge of the nature of geomagnetic storms and their relationships with the conditions of the space environment at the outer part of the Earth's magnetosphere(bow shock nose) is essential to increase our...Proper knowledge of the nature of geomagnetic storms and their relationships with the conditions of the space environment at the outer part of the Earth's magnetosphere(bow shock nose) is essential to increase our resilience to space weather disturbances. In this article, we present an analysis of the interplanetary magnetic field(IMF) and solar wind parameters relevant to 100 geomagnetic storms in Solar Cycle 24. We revisit the relationship between the minimum disturbance storm time index(Dst_(min)), the minimum southward IMF(B_(S, min)), the maximum solar wind density(N_(SW, max)) and speed(V_(max)), and the lag time between the extrema(dT(B_(z), N),dT(B_(z), V)). We end with a regression formula that fits the data, with a coefficient of determination of 0.58, a root mean square error of 21.30 nT, and a mean absolute error of 15.87 nT. Even though more complex machine learning models can outperform this model, it serves as a theoretically sensible alternative for understanding and forecasting geomagnetic storms.展开更多
Geomagnetic storms are rapid disturbances of the Earth’s magnetosphere.They are related to many geophysical phenomena and have large influences on human activities.Observing and studying geomagnetic storms is thus of...Geomagnetic storms are rapid disturbances of the Earth’s magnetosphere.They are related to many geophysical phenomena and have large influences on human activities.Observing and studying geomagnetic storms is thus of great significance to both scientific research and geomagnetic hazards prevention.The Macao Science Satellite-1(MSS-1)project includes two high-precision Chinese geomagnetic satellites successfully launched on May 21,2023.The main purpose of MSS-1 is to accurately measure the Earth’s magnetic field.Here,we analyze early MSS-1 geomagnetic field measurements and report observations of two recent geomagnetic storms that occurred on March 24,2024 and May 11,2024.We also calculate the related geoelectric fields as an initial step towards a quantitative assessment of geomagnetic hazards.展开更多
Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mes...Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.展开更多
Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potenti...Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potentially affecting severe convective storms.Here,we investigate the remote impacts of fires in the western United States(WUS)on the occurrence of large hail(size:≥2.54 cm)in the central US(CUS)over the 20-year period of 2001–20 using the machine learning(ML),Random Forest(RF),and Extreme Gradient Boosting(XGB)methods.The developed RF and XGB models demonstrate high accuracy(>90%)and F1 scores of up to 0.78 in predicting large hail occurrences when WUS fires and CUS hailstorms coincide,particularly in four states(Wyoming,South Dakota,Nebraska,and Kansas).The key contributing variables identified from both ML models include the meteorological variables in the fire region(temperature and moisture),the westerly wind over the plume transport path,and the fire features(i.e.,the maximum fire power and burned area).The results confirm a linkage between WUS fires and severe weather in the CUS,corroborating the findings of our previous modeling study conducted on case simulations with a detailed physics model.展开更多
Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorm...Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorms under different interplanetary conditions,have usually been ignored in previous studies.In this study,97 intense geomagnetic storms(Dstmin≤–100 nT)between 1998 and 2018 were studied statistically using the double superposed epoch analysis(DSEA)and normalized superposed epoch analysis(NSEA)methods.These storms are categorized into two types according to different interplanetary magnetic field(IMF)Bz orientations:geomagnetic storms whose IMF is northward,both upstream and downstream relative to the interplanetary shock,and geomagnetic storms whose upstream and downstream IMF is consistently southward.We further divide these two types into two subsets,by different geomagnetic storm profiles:Type Ⅰ/Type Ⅱ—one/two-step geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock;Type Ⅲ/TypeⅣ—one/two-step geomagnetic storms with southward IMF both upstream and downstream of the interplanetary shock.The results show that:(1)geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock have a clear initial phase;geomagnetic storms with southward IMF in both upstream and downstream of the interplanetary shock do not;(2)the IMF is an important controlling factor in affecting the intensity characteristics of substorms.When Bz is positive before and after the interplanetary shock arrival,the Auroral Electrojet(AE)index changes gently during the initial phase of geomagnetic storms,the median value of AE index is maintained at 500–1000 nT;(3)when Bz is negative before and after the interplanetary shock arrival,the AE index rises rapidly and reaches its maxmum value about one hour after storm sudden commencements(SSC),although the time is scaled between reference points and the maximum value of AE is usually greater than 1,000 nT,representing intense substorms;(4)for most cases,the Dst0 usually reaches its minimum at least one hour after Bz.These results are useful in improving contemporary space weather models,especially for those that address geomagnetic storms and substorms.展开更多
Based on the available original dust storm records from 60 meteorological stations, we discussed the identification standard of severe dust storms at a single station and constructed a quite complete time series of se...Based on the available original dust storm records from 60 meteorological stations, we discussed the identification standard of severe dust storms at a single station and constructed a quite complete time series of severe group dust storms in the eastern part of Northwest China in 1954–2001. The result shows that there were 99 severe group dust storms in this region in recent 48 years. The spatial distribution indicates that the Alax Plateau, most parts of the Ordos Plateau and most parts of the Hexi Corridor are the main areas influenced by severe group dust storms. In addition, the season and the month with the most frequent severe group dust storms are spring and April, accounting for 78.8% and 41.4% of the total events respectively. During the past 48 years the lowest rate of severe group dust storms occurred in the 1990s. Compared with the other 4 decades, on the average, the duration and the affected area of severe group dust storms are relatively short and small during the 1990s. In 2000 and 2001, there were separately 4 severe group dust storms as the higher value after 1983 in the eastern part of Northwest China.展开更多
本文设计了一个基于Lab VIEW平台的LEGO Mind storms轮式机器人运动轨迹实时绘制系统,本系统采用上下位机结构,使用Lab VIEW的图形化编程功能,设计了简单易用的上位机人机界面,并通过相关的函数模块化实现了对轮式机器人的控制和运动轨...本文设计了一个基于Lab VIEW平台的LEGO Mind storms轮式机器人运动轨迹实时绘制系统,本系统采用上下位机结构,使用Lab VIEW的图形化编程功能,设计了简单易用的上位机人机界面,并通过相关的函数模块化实现了对轮式机器人的控制和运动轨迹实时绘制功能。本文重点探讨了基于机器人移动方向的角度值和移动距离值,对绘制运动轨迹所需的平面坐标值的计算和机器人运动轨迹的绘制。展开更多
In this paper, the behavior of TEC at three stations located in the Arctic and Antarctic sectors during some intense geomagnetic storms in the period 2012-2016 is analyzed. The results show the opposite storm effects ...In this paper, the behavior of TEC at three stations located in the Arctic and Antarctic sectors during some intense geomagnetic storms in the period 2012-2016 is analyzed. The results show the opposite storm effects in the Arctic and Antarctic regions. Both the positive and negative TEC disturbances presented more fluctuations over the Arctic stations than over the Antarctic stations. Moreover, the positive TEC disturbances were more significant in winter. The negative disturbances were generally long-lasting,sometimes interrupted by short-duration positive disturbances. Overall, the increases and decreases in TEC can be mainly attributed to changes(i.e., increase and decreases in the O/N_2 ratio respectively) in the thermospheric composition, but prompt penetration electric field could be responsible for the initial TEC disturbances. The thermospheric circulation and the disturbance dynamo, which are maintained due to prolonged high-energy input at high latitudes, can also play important roles at the end of main phase and during recovery phase.展开更多
In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridiona...In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides.This process,when coupled with deep convection,could be an important part of the short-term atmospheric dynamics of water escape.However,the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated.In this work,we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide(DW1)at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database(MCD)5.3,a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well.We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years(MYs)24 to 32.Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1.The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons.During regional dust storms,the tidal transport induces only limited diurnal motion of the water vapor.However,the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid-to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm.The tidal transport process during these two global dust storms can induce opposite effects on water escape.展开更多
In the paper the high latitude ionospheric absorption events, monitored by an imaging riometer at Zhongshan Station, Antarctica, are examined during magnetic storms in early May, 1998. The storm absorption at ~0639 UT...In the paper the high latitude ionospheric absorption events, monitored by an imaging riometer at Zhongshan Station, Antarctica, are examined during magnetic storms in early May, 1998. The storm absorption at ~0639 UT on May 2 was mainly an equatorward progressing absorption event, which were associated with a strong negative bay of the magnetic H component and with a large Pc3 range pulsation. There was a time lag of about 1. 5 hours between the onset of the ionospheric disturbance and the IMF southward turning in the solar wind. The event at 2222 UT on May 2 was a typical midnight absorption spike event. The absorption region took the form of an elongated strip with the length of 100 - 150 km and the width of 30 - 40 km. The absorption during 0830 - 1200 UT on May 6 was a polar cap absorption (PCA) event,caused by intense precipitation of high-energy protons erupted after a large solar flare explosion.展开更多
Based on the composite analysis method, 12 rainstorms triggered by Bay of Bengal storms (shortened as B-storms hereafter) across the whole province of Yunnan were studied, and some interesting results of rain and circ...Based on the composite analysis method, 12 rainstorms triggered by Bay of Bengal storms (shortened as B-storms hereafter) across the whole province of Yunnan were studied, and some interesting results of rain and circulation characteristics influenced by the storms were obtained for low-latitude plateau. Usually, when a rainstorm weather occurs in low-latitude plateau, the B-storm center locates in the central, east or north parts of the Bay of Bengal. At the same time, the subtropical high ridge moves to 15°N– 20°N and the west ridge point moves to the Indo-china Peninsula from the South China Sea and the low-latitude plateau is controlled by southwest air streams coming from the front of the trough and the periphery of the subtropical high. The southwest low-level jet stream from the east side of the bay storm has great effect on heavy rains. On the one hand, the southwest low-level jet stream is playing the role of transporting water vapor and energy. On the other hand, the southwest low-level jet stream is helpful to keep essential dynamical condition. From the analysis of the satellite cloud imagery, it is found that mesoscale convection cloud clusters will keep growing and moving into the low-latitude plateau to cause heavy rains when a storm forms in the Bay of Bengal.展开更多
known aridity of the region is a major factor in promoting numerous dust storms. They have many diverse impacts on the environment and the climate of the region. The classification of dust storms and synoptic conditio...known aridity of the region is a major factor in promoting numerous dust storms. They have many diverse impacts on the environment and the climate of the region. The classification of dust storms and synoptic conditions related to their formation in Central Asia are discussed in the content of their diverse impact. We address dust optical properties that are representative of the region. Dust storms significantly reduce visibly and pose a human health threads. They also cause a significant impact on the radiative regime. As a result, dust storms may cause a decrease in temperature during daytime of up to 16℃ and an increase in temperature during night time from up to 7℃ compared to a clear day.展开更多
The heating of the ionosphere-thermosphere system at high latitudes is a rather common phenomenon in the space climate.During geomagnetic storm time, Joule-heating enhances at high altitudes.The heating generates atmo...The heating of the ionosphere-thermosphere system at high latitudes is a rather common phenomenon in the space climate.During geomagnetic storm time, Joule-heating enhances at high altitudes.The heating generates atmospheric upwelling causing large changes in thermospheric composition and hence in the total mass density.The CHAMP satellite with its complementary payload and long-duration mission provides an excellent dataset for studying the storm-related heating of the upper atmosphere.Based on the four-year accelerometer measurements,density enhancements in polar cap region are observed展开更多
Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number fr...Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz〈-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.展开更多
Salt desert,saline-alkaline dust storm and saline-alkaline mixed dust storm are significant but ignored problems for a long time.After many years of observations and researches,the author believes that salt desert,sal...Salt desert,saline-alkaline dust storm and saline-alkaline mixed dust storm are significant but ignored problems for a long time.After many years of observations and researches,the author believes that salt desert,saline-alkaline dust展开更多
基金funded by NSFC under grants 12250014, 42250101 and 12403068supported by youth funding of Jiangsu province BK20241707+1 种基金supported by the Macao FoundationXinjiang Uygur Autonomous Region for the support through “Tianchi Talent” special expert project。
文摘Strong flares and/or coronal mass ejections(CMEs) could bring us disastrous space weather,destroy crucial technology in space,and cause a large-scale blackout during some extreme cases.They frequently cause geomagnetic storms,which is a sudden disturbance of the Earth's magnetosphere.It is well accepted that CMEs play a dominant role in causing geomagnetic storms by a direct impact,but it is still not very clear regarding their association with solar flares.The association would be helpful for forecasting geomagnetic storms directly from flares,which are much easier to observe.The Macao Science Satellite-1(MSS-1) mission,with the scientific aim of studying the origin and evolution of the geomagnetic field,is able to accurately measure the vector geomagnetic field.Besides,it measures rapid spectral evolution of the solar X-ray irradiance of solar flares.In this study,we analyzed measurements by MSS-1 during a series of X-class flares in October of 2024,and saw the relationship between the flares and the associated geomagnetic storms.The observations support that the major geomagnetic storms tend to be associated with flares' duration in addition to flare class.We also find that long duration ones have radiated more energy in the extreme ultraviolet waveband.Being equally important,our results show that the magnetic fields measured by MSS-1,especially its external(e_(1)^(0)) coefficient,can well be used for monitoring the geomagnetic disturbance.
基金supported by the National Natural Science Foundation of China(Grant No.42305013)Joint Research Project for Meteorological Capacity Improvement(Grant Nos.23NLTSQ002 and 24NLTSQ001)+2 种基金China Meteorological Administration Tornado Key Laboratory(Grant No.TKL202307)the China Meteorological Administration Youth Innovation Team Fund(Grant No.CMA2024QN05)a research project of the Chinese Academy of Meteorological Science(Grant No.2023Z019)。
文摘This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic linkages with Northeast China cold vortices(NCCVs)of tornadic storms under different convective modes.Results reveal that discrete storms account for 70%of events,with clustered cells(CC)being the most frequent mode,while significant tornadoes(EF2+)are primarily associated with isolated cells(IC)and broken lines(BL).The storm mode distribution in northeastern China resembles that of the central United States but with a higher proportion of CC and lower IC.In contrast,southern China exhibits a higher frequency of quasi-linear(QL)modes(>50%),similar to European patterns.Although no single parameter clearly differentiates between all tornado modes,distinct morphological characteristics emerge through specific parameter combinations:NL modes are characterized by high 0-1 km storm-relative helicity(SRH1)and humidity but low 0-6 km shear(SR6),whereas IC modes display contrasting features with low SRH1 and high CAPE.Notably,83%of tornadoes are associated with NCCVs,preferentially forming in southeastern/southwestern quadrants.Strong tornadoes favor southeastern quadrants,while NCCV intensity correlates with tornadic distance from vortex centers.Three characteristic synoptic configurations emerge:(T1)strong deep vortices with vertically aligned cold troughs,generating southeast-dominant tornado clusters characterized by a high proportion of BL and QL modes;(T2)weaker vortices featuring sub-synoptic troughs,with southern-distributed events dominated by a predominance of the CC mode;(T3)transverse-trough systems exhibiting CAPE-SRH decoupling and reduced tornadic activity.This study enhances our understanding of tornadoes in northeastern China,informing future research on formation mechanisms,prediction methods,and disaster prevention strategies.
文摘The Hong Kong Observatory(HKO)installed an X-band dual-polarization Phased Array Weather Radar(PAWR)at its wind profiler station at Sha Lo Wan(SLW)in 2021 to monitor high-impact weather in Hong Kong.The PAWR could complete a volume scan in one minute with a spatial resolution of 30 meters.Dual polarimetric variables from the SLW PAWR,including differential reflectivity(ZDR),specific differential phase(KDP),and hydro-classification(HCL)products,were used to diagnose the vertical motion and lightning characteristics of mesoscale convective storms(MCS).Through variational data assimilation,three-dimensional(3-D)wind fields were constructed to validate the SLW PAWR observations.Two MCS events that occurred on 18 September 2022 and 17 June 2023 are central to this study.The findings include(1)negative ZDR serves as a good indicator of the occurrence of intense downdrafts associated with an MCS,a premise further supported by the 3-D wind field analysis results,(2)negative KDP suggested the formation of vertically aligned ice crystals which facilitated cloud electrification,and(3)HCL products indicated the presence of mixed ice crystals and graupel above the 0℃melting layer which promoted active cloud-to-cloud and cloud-to-ground lightning strokes.These results show that the SLW PAWR provides essential observations,which,when coupled with 3-D wind field analysis,can aid in enhancing the understanding of the dynamics and electrification processes within an MCS.
基金the Deanship of Graduate Studies and Scientific Research at Qassim University for financial support(QU-APC-2024-9/1).
文摘Control signaling is mandatory for the operation and management of all types of communication networks,including the Third Generation Partnership Project(3GPP)mobile broadband networks.However,they consume important and scarce network resources such as bandwidth and processing power.There have been several reports of these control signaling turning into signaling storms halting network operations and causing the respective Telecom companies big financial losses.This paper draws its motivation from such real network disaster incidents attributed to signaling storms.In this paper,we present a thorough survey of the causes,of the signaling storm problems in 3GPP-based mobile broadband networks and discuss in detail their possible solutions and countermeasures.We provide relevant analytical models to help quantify the effect of the potential causes and benefits of their corresponding solutions.Another important contribution of this paper is the comparison of the possible causes and solutions/countermeasures,concerning their effect on several important network aspects such as architecture,additional signaling,fidelity,etc.,in the form of a table.This paper presents an update and an extension of our earlier conference publication.To our knowledge,no similar survey study exists on the subject.
基金supported by the National Research and Innovation Agency(BRIN),Indonesia.
文摘Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked to equatorial plasma bubbles(EPBs),regions of depleted plasma density that form after sunset.Ionospheric scintillation typically occurs from post-sunset hours until midnight.Post-sunset EPBs can be enhanced or suppressed during geomagnetic storms,depending on local sunset timing and how it relates to the storm's main or recovery phases.This study analyzes ionospheric scintillation in Indonesia,located at low geomagnetic and geographic latitudes,during geomagnetic events from 2003 to 2024.Using the S4 index,scintillation was examined with data from seven observation stations during geomagnetic storm events.Geomagnetic activity was evaluated using Dst,SYM-H,and AE indices,employing Superposed Epoch Analysis(SEA)to assess scintillation occurrence linked to minimum SYM-H,defined as epoch 0 to represent the storm peak or the onset of recovery phase in each event.The analysis categorized geomagnetic storms into weak-moderate(–100 nT<min.Dst≤–30 nT)and strong(min.Dst≤–100 nT),and examined their dependence on the local time of minimum SYM-H.Results indicate that scintillation first appears~6 hours after epoch 0 in weak-moderate geomagnetic storms,and~12 hours after epoch 0 in strong geomagnetic storms.The average AE index returns to its baseline value(quiet condition)~6 and~12 hours after epoch 0 for weak-moderate and strong geomagnetic storms,respectively.Further analysis based on the classification of the local time of epoch 0 shows that scintillation occurrence is not observed in post-sunset hours when epoch 0 falls between 16:00 and 19:00 LT for weak-moderate geomagnetic storms.In strong geomagnetic storms,scintillation occurrence during post-sunset hours is absent when epoch 0 is between 10:00 and 19:00 LT.Notably,when the minimum SYM-H(epoch 0)nearly coincides with local sunset,scintillation activity occurs around sunset in both weak-moderate and strong geomagnetic storms.Furthermore,when epoch 0 falls within midnight until early morning,scintillation can be generated in the post-sunset hours before epoch 0.Still,post-midnight scintillation is not observed in the equatorial region during the recovery phase of either weak-moderate and strong storm events.Our findings show that when sunset falls before or coincide with epoch 0,the likelihood of post-sunset EPB and scintillation increases,due to the prompt-penetration electric field(PPEF)in the main phase of storm.The disturbance dynamo electric field(DDEF)in the recovery phase driven by equatorward winds from auroral Joule heating operates for at least 6-and 12-hours post-epoch 0 in the cases of weak-moderate and strong geomagnetic storms,respectively.When the local sunset falls within these operational DDEF periods,post-sunset EPBs will likely be suppressed,inhibiting ionospheric scintillation during post-sunset hours.Finally,this study provides essential information for developing more accurate ionospheric scintillation prediction models in space weather services in equatorial regions.
文摘Proper knowledge of the nature of geomagnetic storms and their relationships with the conditions of the space environment at the outer part of the Earth's magnetosphere(bow shock nose) is essential to increase our resilience to space weather disturbances. In this article, we present an analysis of the interplanetary magnetic field(IMF) and solar wind parameters relevant to 100 geomagnetic storms in Solar Cycle 24. We revisit the relationship between the minimum disturbance storm time index(Dst_(min)), the minimum southward IMF(B_(S, min)), the maximum solar wind density(N_(SW, max)) and speed(V_(max)), and the lag time between the extrema(dT(B_(z), N),dT(B_(z), V)). We end with a regression formula that fits the data, with a coefficient of determination of 0.58, a root mean square error of 21.30 nT, and a mean absolute error of 15.87 nT. Even though more complex machine learning models can outperform this model, it serves as a theoretically sensible alternative for understanding and forecasting geomagnetic storms.
基金supported financially by the National Natural Science Foundation of China(42250101)the Macao Foundation and Macao Science and Technology Development Fund(0001/2019/A1).
文摘Geomagnetic storms are rapid disturbances of the Earth’s magnetosphere.They are related to many geophysical phenomena and have large influences on human activities.Observing and studying geomagnetic storms is thus of great significance to both scientific research and geomagnetic hazards prevention.The Macao Science Satellite-1(MSS-1)project includes two high-precision Chinese geomagnetic satellites successfully launched on May 21,2023.The main purpose of MSS-1 is to accurately measure the Earth’s magnetic field.Here,we analyze early MSS-1 geomagnetic field measurements and report observations of two recent geomagnetic storms that occurred on March 24,2024 and May 11,2024.We also calculate the related geoelectric fields as an initial step towards a quantitative assessment of geomagnetic hazards.
基金the National Key R&D Program of China(Grant No.2022YFF0503702)the National Natural Science Foundation of China(Grant Nos.42004132,42074195 and 42074183)+1 种基金the open funding of the Ministry of Natural Resources Key Laboratory for Polar Science(Grant No.KP202104)the China Geological Survey(Grant No.ZD20220145).
文摘Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.
基金supported by the U.S.Department of Energy,Office of Science,Office of Biological and Environmental Research program as part of the Regional and Global Model Analysis and Multi-Sector Dynamics program areas(Award Number DE-SC0016605)Argonne National Laboratory is operated for the DOE by UChicago Argonne,LLC,under contract DE-AC02-06CH11357+1 种基金the National Energy Research Scientific Computing Center(NERSC)NERSC is a U.S.DOE Office of Science User Facility operated under Contract DE-AC02-05CH11231.
文摘Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potentially affecting severe convective storms.Here,we investigate the remote impacts of fires in the western United States(WUS)on the occurrence of large hail(size:≥2.54 cm)in the central US(CUS)over the 20-year period of 2001–20 using the machine learning(ML),Random Forest(RF),and Extreme Gradient Boosting(XGB)methods.The developed RF and XGB models demonstrate high accuracy(>90%)and F1 scores of up to 0.78 in predicting large hail occurrences when WUS fires and CUS hailstorms coincide,particularly in four states(Wyoming,South Dakota,Nebraska,and Kansas).The key contributing variables identified from both ML models include the meteorological variables in the fire region(temperature and moisture),the westerly wind over the plume transport path,and the fire features(i.e.,the maximum fire power and burned area).The results confirm a linkage between WUS fires and severe weather in the CUS,corroborating the findings of our previous modeling study conducted on case simulations with a detailed physics model.
文摘Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorms under different interplanetary conditions,have usually been ignored in previous studies.In this study,97 intense geomagnetic storms(Dstmin≤–100 nT)between 1998 and 2018 were studied statistically using the double superposed epoch analysis(DSEA)and normalized superposed epoch analysis(NSEA)methods.These storms are categorized into two types according to different interplanetary magnetic field(IMF)Bz orientations:geomagnetic storms whose IMF is northward,both upstream and downstream relative to the interplanetary shock,and geomagnetic storms whose upstream and downstream IMF is consistently southward.We further divide these two types into two subsets,by different geomagnetic storm profiles:Type Ⅰ/Type Ⅱ—one/two-step geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock;Type Ⅲ/TypeⅣ—one/two-step geomagnetic storms with southward IMF both upstream and downstream of the interplanetary shock.The results show that:(1)geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock have a clear initial phase;geomagnetic storms with southward IMF in both upstream and downstream of the interplanetary shock do not;(2)the IMF is an important controlling factor in affecting the intensity characteristics of substorms.When Bz is positive before and after the interplanetary shock arrival,the Auroral Electrojet(AE)index changes gently during the initial phase of geomagnetic storms,the median value of AE index is maintained at 500–1000 nT;(3)when Bz is negative before and after the interplanetary shock arrival,the AE index rises rapidly and reaches its maxmum value about one hour after storm sudden commencements(SSC),although the time is scaled between reference points and the maximum value of AE is usually greater than 1,000 nT,representing intense substorms;(4)for most cases,the Dst0 usually reaches its minimum at least one hour after Bz.These results are useful in improving contemporary space weather models,especially for those that address geomagnetic storms and substorms.
基金The National Key Basic Research Project of China, No. G2000048703 The Knowledge Innovation Project of CAS, No. KZCX2-305 Key Research Project of NSMC, No.NSMC-Y0101
文摘Based on the available original dust storm records from 60 meteorological stations, we discussed the identification standard of severe dust storms at a single station and constructed a quite complete time series of severe group dust storms in the eastern part of Northwest China in 1954–2001. The result shows that there were 99 severe group dust storms in this region in recent 48 years. The spatial distribution indicates that the Alax Plateau, most parts of the Ordos Plateau and most parts of the Hexi Corridor are the main areas influenced by severe group dust storms. In addition, the season and the month with the most frequent severe group dust storms are spring and April, accounting for 78.8% and 41.4% of the total events respectively. During the past 48 years the lowest rate of severe group dust storms occurred in the 1990s. Compared with the other 4 decades, on the average, the duration and the affected area of severe group dust storms are relatively short and small during the 1990s. In 2000 and 2001, there were separately 4 severe group dust storms as the higher value after 1983 in the eastern part of Northwest China.
文摘本文设计了一个基于Lab VIEW平台的LEGO Mind storms轮式机器人运动轨迹实时绘制系统,本系统采用上下位机结构,使用Lab VIEW的图形化编程功能,设计了简单易用的上位机人机界面,并通过相关的函数模块化实现了对轮式机器人的控制和运动轨迹实时绘制功能。本文重点探讨了基于机器人移动方向的角度值和移动距离值,对绘制运动轨迹所需的平面坐标值的计算和机器人运动轨迹的绘制。
文摘In this paper, the behavior of TEC at three stations located in the Arctic and Antarctic sectors during some intense geomagnetic storms in the period 2012-2016 is analyzed. The results show the opposite storm effects in the Arctic and Antarctic regions. Both the positive and negative TEC disturbances presented more fluctuations over the Arctic stations than over the Antarctic stations. Moreover, the positive TEC disturbances were more significant in winter. The negative disturbances were generally long-lasting,sometimes interrupted by short-duration positive disturbances. Overall, the increases and decreases in TEC can be mainly attributed to changes(i.e., increase and decreases in the O/N_2 ratio respectively) in the thermospheric composition, but prompt penetration electric field could be responsible for the initial TEC disturbances. The thermospheric circulation and the disturbance dynamo, which are maintained due to prolonged high-energy input at high latitudes, can also play important roles at the end of main phase and during recovery phase.
基金This work is supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(grant XDB41000000)the pre-research project on Civil Aerospace Technologies of the China National Space Administration(grant D020105).T.L.and J.C.acknowledge support from the National Natural Science Foundation of China through grants 41525015 and 41774186 to J.C.,and grants 41674149 and 41974175 to T.L.X.Z.acknowledges support from the National Science Foundation(grant AST1740921).J.L.acknowledges support from the Open Research Program of the Chinese Academy of Sciences Key Laboratory of Geospace Environment.Z.W.acknowledges support from the Guangdong Basic and Applied Basic Research Foundation(grant 2019A1515110815)the Chinese Academy of Sciences Key Laboratory of Lunar and Deep Space Exploration(grant LDSE201803).We would like to thank the MCD teams for making the MCD 5.3 data sets available online at http://www-mars.lmd.jussieu.fr/mars/access.html.
文摘In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides.This process,when coupled with deep convection,could be an important part of the short-term atmospheric dynamics of water escape.However,the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated.In this work,we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide(DW1)at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database(MCD)5.3,a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well.We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years(MYs)24 to 32.Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1.The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons.During regional dust storms,the tidal transport induces only limited diurnal motion of the water vapor.However,the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid-to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm.The tidal transport process during these two global dust storms can induce opposite effects on water escape.
文摘In the paper the high latitude ionospheric absorption events, monitored by an imaging riometer at Zhongshan Station, Antarctica, are examined during magnetic storms in early May, 1998. The storm absorption at ~0639 UT on May 2 was mainly an equatorward progressing absorption event, which were associated with a strong negative bay of the magnetic H component and with a large Pc3 range pulsation. There was a time lag of about 1. 5 hours between the onset of the ionospheric disturbance and the IMF southward turning in the solar wind. The event at 2222 UT on May 2 was a typical midnight absorption spike event. The absorption region took the form of an elongated strip with the length of 100 - 150 km and the width of 30 - 40 km. The absorption during 0830 - 1200 UT on May 6 was a polar cap absorption (PCA) event,caused by intense precipitation of high-energy protons erupted after a large solar flare explosion.
基金Project of Key Science and Technology and High-tech of Yunnan Province
文摘Based on the composite analysis method, 12 rainstorms triggered by Bay of Bengal storms (shortened as B-storms hereafter) across the whole province of Yunnan were studied, and some interesting results of rain and circulation characteristics influenced by the storms were obtained for low-latitude plateau. Usually, when a rainstorm weather occurs in low-latitude plateau, the B-storm center locates in the central, east or north parts of the Bay of Bengal. At the same time, the subtropical high ridge moves to 15°N– 20°N and the west ridge point moves to the Indo-china Peninsula from the South China Sea and the low-latitude plateau is controlled by southwest air streams coming from the front of the trough and the periphery of the subtropical high. The southwest low-level jet stream from the east side of the bay storm has great effect on heavy rains. On the one hand, the southwest low-level jet stream is playing the role of transporting water vapor and energy. On the other hand, the southwest low-level jet stream is helpful to keep essential dynamical condition. From the analysis of the satellite cloud imagery, it is found that mesoscale convection cloud clusters will keep growing and moving into the low-latitude plateau to cause heavy rains when a storm forms in the Bay of Bengal.
文摘known aridity of the region is a major factor in promoting numerous dust storms. They have many diverse impacts on the environment and the climate of the region. The classification of dust storms and synoptic conditions related to their formation in Central Asia are discussed in the content of their diverse impact. We address dust optical properties that are representative of the region. Dust storms significantly reduce visibly and pose a human health threads. They also cause a significant impact on the radiative regime. As a result, dust storms may cause a decrease in temperature during daytime of up to 16℃ and an increase in temperature during night time from up to 7℃ compared to a clear day.
文摘The heating of the ionosphere-thermosphere system at high latitudes is a rather common phenomenon in the space climate.During geomagnetic storm time, Joule-heating enhances at high altitudes.The heating generates atmospheric upwelling causing large changes in thermospheric composition and hence in the total mass density.The CHAMP satellite with its complementary payload and long-duration mission provides an excellent dataset for studying the storm-related heating of the upper atmosphere.Based on the four-year accelerometer measurements,density enhancements in polar cap region are observed
基金supported by the project Environment Building for S&T Industries (2005DKA64000)
文摘Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz〈-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.
文摘Salt desert,saline-alkaline dust storm and saline-alkaline mixed dust storm are significant but ignored problems for a long time.After many years of observations and researches,the author believes that salt desert,saline-alkaline dust
