Starting from the Bay of Bengal storm,based on conventional meteorological data,FY2G meteorological satellite data,EC fine grid data and ERA5 reanalysis data,the first rainstorm process in Dehong Prefecture in the ear...Starting from the Bay of Bengal storm,based on conventional meteorological data,FY2G meteorological satellite data,EC fine grid data and ERA5 reanalysis data,the first rainstorm process in Dehong Prefecture in the early summer of 2024 was analyzed.The results show that the strengthening and northeastward movement of the Bay of Bengal storm"Remal"was the main influencing system for the generation of continuous heavy precipitation in Dehong Prefecture from May 25 to 27,2024.The establishment and strengthening of the low-level southwest jet stream provided better dynamic,water vapor and energy conditions for the generation of this heavy precipitation.The generation and maintenance of rainstorm required the transportation of a steady stream of water vapor to the rainstorm area,and there was strong convergence of water vapor in the rainstorm area.Therefore,in the forecast of summer rainstorm,whether the low-level jet stream is generated or not is very important for the forecast of rainstorm.In addition,there was a good corresponding relationship between the falling area of heavy precipitation,precipitation intensity and duration,and low-level water vapor convergence area.The establishment of southwest monsoon is of great significance to the beginning date of rainy season in Dehong Prefecture.The beginning date of rainy season in Dehong Prefecture was closely related to the first rainstorm process in Dehong Prefecture in early summer.In the future prediction of the beginning date of rainy season in Dehong Prefecture,the first statewide rainstorm process in early summer should be the key point for the prediction.展开更多
Timely and accurate forecasting of storm surges can effectively prevent typhoon storm surges from causing large economic losses and casualties in coastal areas.At present,numerical model forecasting consumes too many ...Timely and accurate forecasting of storm surges can effectively prevent typhoon storm surges from causing large economic losses and casualties in coastal areas.At present,numerical model forecasting consumes too many resources and takes too long to compute,while neural network forecasting lacks regional data to train regional forecasting models.In this study,we used the DUAL wind model to build typhoon wind fields,and constructed a typhoon database of 75 processes in the northern South China Sea using the coupled Advanced Circulation-Simulating Waves Nearshore(ADCIRC-SWAN)model.Then,a neural network with a Res-U-Net structure was trained using the typhoon database to forecast the typhoon processes in the validation dataset,and an excellent storm surge forecasting effect was achieved in the Pearl River Estuary region.The storm surge forecasting effect of stronger typhoons was improved by adding a branch structure and transfer learning.展开更多
This study utilizes radio occultation observations from the Macao Science Satellite-1 mission(MSS-1)to investigate ionospheric response to the May 2024 G5 geomagnetic storm within the South Atlantic Anomaly(SAA)region...This study utilizes radio occultation observations from the Macao Science Satellite-1 mission(MSS-1)to investigate ionospheric response to the May 2024 G5 geomagnetic storm within the South Atlantic Anomaly(SAA)region.The distinctive data from MSS-1,complemented by observations from the ground-based Global Navigation Satellite System(GNSS)and the Constellation Observing System for Meteorology,Ionosphere,and Climate follow-on satellite mission(COSMIC-2),reveal a super plasma fountain effect during the main phase of the storm.This effect was marked by peaks in the equatorial ionization anomaly that extended beyond their typical latitude range.The MSS-1 observations,particularly in the northern hemisphere of the SAA region,confirm the role of prompt penetration electric fields in driving ionospheric disturbances and amplifying scintillation at higher altitudes.The study also identifies a decrease in total electron content and a reduction in scintillation occurrence during the recovery phase of the storm.The results demonstrate the pivotal role that MSS-1 observations can play,when combined with ground-based and COSMIC-2 observations,in providing a more comprehensive understanding of ionospheric response to severe geomagnetic storms.展开更多
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
The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospher...The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.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
Storm surge events(SSEs)involve multiple hazard-causing factors,such as surges,extreme rainfall,strong winds,waves,and ocean currents,which have destructive impacts on coastal regions.For a quantitative multi-hazard a...Storm surge events(SSEs)involve multiple hazard-causing factors,such as surges,extreme rainfall,strong winds,waves,and ocean currents,which have destructive impacts on coastal regions.For a quantitative multi-hazard assessment of SSEs,this study introduced the concept of the storm surge event seawater-atmosphere system(SSE-SAS)and proposed the system energy equivalence(SEE)model from a systemic energy perspective.SEE was obtained by employing a parameterization approach,and the hazard index(HI)and the concept of most significant hazard(MSH)were adopted to evaluate the severity of SSE-SAS.SEE at five stations in the Shandong Peninsula was calculated from 2005 to 2019,and probability analysis and hazard assessment were further conducted.Results show that the SEE of SSE-SAS ranges from 0.029×10^(3) to 30.418×10^(3) J/m^(2),and it exhibits an insignificant decreasing trend from 2005 to 2019.The SEE of SSE-SAS in the west of the Shandong Peninsula is greater than that in the east.Moreover,storm waves,storm surges,and storm rainfall are the major contributors to SEE,which exhibit different spatial patterns and characters in different SSE-SAS types.The HI of SSE-SAS at five stations is no more than medium hazard level,with MSH at return periods of 2-to 4-year level.This study provides a new approach for quantifying multi-hazard SSEs,which offers scientific insights for regional multi-hazard risk reduction and mitigation efforts.展开更多
The local time-stepping(LTS)algorithm is an adaptive method that adjusts the time step by selecting suitable intervals for different regions based on the spatial scale of each cell and water depth and flow velocity be...The local time-stepping(LTS)algorithm is an adaptive method that adjusts the time step by selecting suitable intervals for different regions based on the spatial scale of each cell and water depth and flow velocity between cells.The method can be optimized by calculating the maximum power of two of the global time step increments in the domain,allowing the optimal time step to be approached throughout the grid.To verify the acceleration and accuracy of LTS in storm surge simulations,we developed a model to simulate astronomical storm surges along the southern coast of China.This model employs the shallow water equations as governing equations,numerical discretization using the finite volume method,and fluxes calculated by the Roe solver.By comparing the simulation results of the traditional global time-stepping algorithm with those of the LTS algorithm,we find that the latter fit the measured data better.Taking the calculation results of Typhoon Sally in 1996 as an example,we show that compared with the traditional global time-stepping algorithm,the LTS algorithm reduces computation time by 2.05 h and increases computation efficiency by 2.64 times while maintaining good accuracy.展开更多
Arid West Asia(AWA)is a critical hub of the Silk Road and one of the primary dust source regions in the Northern Hemisphere.Dust storms in AWA emitting substantial dust particles into the atmosphere,significantly infl...Arid West Asia(AWA)is a critical hub of the Silk Road and one of the primary dust source regions in the Northern Hemisphere.Dust storms in AWA emitting substantial dust particles into the atmosphere,significantly influencing air quality,climate change and marine productivity.However,the variability of dust storm activity in this region during the Holocene,particularly its links to vegetation and hydroclimatic changes,remains debated,hindering our understanding of the interconnected dynamics between climate change and surface environments.This study reconstructs dust storm variations in AWA over the past 9000 years using geochemical analyses(trace elements,Sr-Nd isotopes)from a well-dated,high-resolution sediment core from the Almalou Peatland,located on the western Iranian Plateau.Our results reveal a decline in dust storm frequency from the early to mid-Holocene,a minimum occurrence during the mid-Holocene,and a significant increase in the late Holocene.Provenance analysis indicates that the primary dust sources were the arid regions of Mesopotamia,located upwind of the study area.A comparison with proxy records and paleoclimate models suggests an inverse relationship between dust storm activity and regional hydroclimatic and vegetation changes,along with a positive correlation with wind speeds.The concentration of dust storms during the wetter month of May highlights wind speed as a more critical driving factor.Moreover,given the dominant influence of the subtropical high on hydroclimatic conditions and wind speeds in AWA,we propose that this system is the key regulator of regional dust storm dynamics.Our findings provide new insights into the drivers of dust storm activity in AWA and hold implications for developing targeted dust storm management strategies.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
To investigate the effect of typhoon path translation on storm surge augmentation,the storm surge during Typhoon 1909 Lekima in the East China Sea is simulated using Delft 3D.The model sets up three scenarios to analy...To investigate the effect of typhoon path translation on storm surge augmentation,the storm surge during Typhoon 1909 Lekima in the East China Sea is simulated using Delft 3D.The model sets up three scenarios to analyze the path’s effect on storm surge in the Shandong Peninsula Sea by shifting the typhoon path to the east and west.Results show that the areas of maximum storm surge in each scenario are located on both sides of the typhoon path and shift along with its movement.When the typhoon path shifts eastward,the maximum storm surge intensifies at Zhifu Island station 8 hours earlier.Conversely,a westward shift in the typhoon track leads to a maximum storm surge increase at Shidao Island station 12 hours earlier.Other scenarios exhibit minimal deviation from the original route.Typhoons penetrating deep inland can induce substantial storm surges,with the most extensive surge area situated in the western part of the Shandong Peninsula.展开更多
The North Pacific storm track(NPST)is a high-frequency area of extratropical cyclones and an important channel for water vapor and energy transfer between low and mid–high latitudes.Previous weather and dynamic studi...The North Pacific storm track(NPST)is a high-frequency area of extratropical cyclones and an important channel for water vapor and energy transfer between low and mid–high latitudes.Previous weather and dynamic studies in this region have made significant progress,but due to the lack of ocean surface rainfall observation data,there is a lack of statistical research on precipitation in this area.In this study,statistical research on the spatiotemporal distribution characteristics of NPST rainfall was conducted based on GPM DPR(Global Precipitation Measurement Dual-frequency Precipitation Radar)observation data and ERA5 atmospheric parameters,and analysis and explanations are provided based on the atmospheric parameters.The study found that,compared to low-pressure systems,pressure gradients have a greater impact on cyclone activity and rainfall distribution.This feature,along with the meridional distribution of high atmospheric water vapor in the North Pacific Ocean and low in the north,collectively leads to the offset of high-frequency rainfall areas relative to storm tracks.The distribution of sea surface temperatures in the North Pacific Ocean affects the zonal distribution of storm tracks,causing weather disturbances and precipitation along the storm tracks to exhibit a northward extension from west to east.This study deepens our understanding of the role of NPST in global-scale water vapor and energy balance,and is of great significance for improving the prediction accuracy of climate models with respect to rainfall generated by extratropical cyclones.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
An intense Asian dust storm invadedQinhuangdao,a coastal city ofNorth China on April 11-14,2023.We analyzed the bulk water-soluble inorganic ions(WSII)of PM_(10)and PM_(2.5)using an Ion Chromatograph and investigated ...An intense Asian dust storm invadedQinhuangdao,a coastal city ofNorth China on April 11-14,2023.We analyzed the bulk water-soluble inorganic ions(WSII)of PM_(10)and PM_(2.5)using an Ion Chromatograph and investigated individual particlemorphology and elemental composition using a scanning electron microscope coupled with energy dispersive X-ray.The results showed when the dust was directly transported to the sampling site from northwestern China(direct transport stages),the PM_(10)mass concentrations were high(675.0μg/m^(3))but the relative humidity(RH)was low.Total WSII were 19.54μg/m^(3)and 11.17μg/m^(3),accounting for 2.90%and 7.25%of the PM_(10)and PM_(2.5),respectively.In addition,the proportion of S-containing individual mineral dust was low(28.7%-35.3%).The results suggested there were limited secondary inorganic aerosol formation.However,when the dust was transported back to the sampling site across the Bohai Sea in the following days(reverse transport stages),both the PM_(10)mass concentrations(462.3μg/m^(3))and RH were high.Total WSII were 43.75μg/m^(3)and 18.71μg/m^(3),accounting for 9.62%and 14.45%of the total PM_(10)and PM_(2.5),respectively.The proportion of S-containing particles was 51.5%-72.5%.In addition,the concentration of NO_(3)^(−)was much higher than that of SO_(4)^(2−).The results suggested both the sulfate and nitrate formation occurred on coarse mineral dust but the nitrate formation exceeded sulfate formation.Interestingly,mostmineral dust,including Sirich particles contained Cl when they passed through the marine atmosphere.The results highlighted the heterogeneous reactions of dust varied in different transport stages.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
Extreme weather events pose an ever-greater threat to people,infrastructure,and nature.Forest ecosystems are highly sensitive to extreme cold events that can disrupt ecosystem functions,especially in montane regions.I...Extreme weather events pose an ever-greater threat to people,infrastructure,and nature.Forest ecosystems are highly sensitive to extreme cold events that can disrupt ecosystem functions,especially in montane regions.Ice storms can be particularly destructive,with rapid ice accretion causing tree branches to break,even snapping or uprooting entire trees.In March 2022,the Shennongjia forest in central China experienced severe ice storm conditions that severely damaged over 230,300ha.We utilized this opportunity to assess the vulnerability of different tree types(coniferous,deciduous,and evergreen broad-leaved)and stand compositions to damage resulting from ice glaze along an elevation gradient from 1,200 to 2,400m a.s.l.Among the 7,144 trees surveyed,10.1%suffered some extent of damage,which was most prolific in the middle elevation zone.While 96.8%of all damage occurred to deciduous broadleaved trees that dominated the forest community,the most severe damage(uprooting and lower trunk breakage)occurred to coniferous trees.The extent and severity of tree damage were moderated by forest composition,with secondary effects of forest structure and slope.Abiotic factors predominantly affected coniferous trees.We emphasize that more research and monitoring are needed to better understand the full impact of extreme weather events on forests,especially as the frequency and intensity of these events increases due to climate change.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
基金Supported by the"Short,Simple and Fast"Project of Meteorological Science and Technology of Dehong Prefecture(DPK2024-01).
文摘Starting from the Bay of Bengal storm,based on conventional meteorological data,FY2G meteorological satellite data,EC fine grid data and ERA5 reanalysis data,the first rainstorm process in Dehong Prefecture in the early summer of 2024 was analyzed.The results show that the strengthening and northeastward movement of the Bay of Bengal storm"Remal"was the main influencing system for the generation of continuous heavy precipitation in Dehong Prefecture from May 25 to 27,2024.The establishment and strengthening of the low-level southwest jet stream provided better dynamic,water vapor and energy conditions for the generation of this heavy precipitation.The generation and maintenance of rainstorm required the transportation of a steady stream of water vapor to the rainstorm area,and there was strong convergence of water vapor in the rainstorm area.Therefore,in the forecast of summer rainstorm,whether the low-level jet stream is generated or not is very important for the forecast of rainstorm.In addition,there was a good corresponding relationship between the falling area of heavy precipitation,precipitation intensity and duration,and low-level water vapor convergence area.The establishment of southwest monsoon is of great significance to the beginning date of rainy season in Dehong Prefecture.The beginning date of rainy season in Dehong Prefecture was closely related to the first rainstorm process in Dehong Prefecture in early summer.In the future prediction of the beginning date of rainy season in Dehong Prefecture,the first statewide rainstorm process in early summer should be the key point for the prediction.
基金supported by the National Natural Science Foundation of China(Grant No.42076214)Natural Science Foundation of Shandong Province(Grant No.ZR2024QD057).
文摘Timely and accurate forecasting of storm surges can effectively prevent typhoon storm surges from causing large economic losses and casualties in coastal areas.At present,numerical model forecasting consumes too many resources and takes too long to compute,while neural network forecasting lacks regional data to train regional forecasting models.In this study,we used the DUAL wind model to build typhoon wind fields,and constructed a typhoon database of 75 processes in the northern South China Sea using the coupled Advanced Circulation-Simulating Waves Nearshore(ADCIRC-SWAN)model.Then,a neural network with a Res-U-Net structure was trained using the typhoon database to forecast the typhoon processes in the validation dataset,and an excellent storm surge forecasting effect was achieved in the Pearl River Estuary region.The storm surge forecasting effect of stronger typhoons was improved by adding a branch structure and transfer learning.
基金support from the National Natural Science Foundation of China(No.42274027)the Fundamental Research Funds for the Central Universitiessupported also by the Macao Foundation。
文摘This study utilizes radio occultation observations from the Macao Science Satellite-1 mission(MSS-1)to investigate ionospheric response to the May 2024 G5 geomagnetic storm within the South Atlantic Anomaly(SAA)region.The distinctive data from MSS-1,complemented by observations from the ground-based Global Navigation Satellite System(GNSS)and the Constellation Observing System for Meteorology,Ionosphere,and Climate follow-on satellite mission(COSMIC-2),reveal a super plasma fountain effect during the main phase of the storm.This effect was marked by peaks in the equatorial ionization anomaly that extended beyond their typical latitude range.The MSS-1 observations,particularly in the northern hemisphere of the SAA region,confirm the role of prompt penetration electric fields in driving ionospheric disturbances and amplifying scintillation at higher altitudes.The study also identifies a decrease in total electron content and a reduction in scintillation occurrence during the recovery phase of the storm.The results demonstrate the pivotal role that MSS-1 observations can play,when combined with ground-based and COSMIC-2 observations,in providing a more comprehensive understanding of ionospheric response to severe geomagnetic storms.
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 Key R&D Program of China (Grant No.2022YFF0503700)the special funds of Hubei Luojia Laboratory (Grant No.220100011)+1 种基金supported by the International Space Science Institute–Beijing(ISSI-BJ) project“The Electromagnetic Data Validation and Scientific Application Research based on CSES Satellite”and ISSI/ISSI-BJ project,“Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction.”
文摘The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.
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 Key Laboratory of Coastal Science and Integrated Management,Ministry of Natural Resources(No.2022COSIMQ002)the Shandong Provincial Social Science Planning Research Project(No.22CXSXJ15)+1 种基金the Guangxi Key Laboratory of Marine Environmental Science,Guangxi Academy of Sciences(No.GXKLHY21-04)the Hainan Province Marxism Project General Program(No.2023HNMGC03).
文摘Storm surge events(SSEs)involve multiple hazard-causing factors,such as surges,extreme rainfall,strong winds,waves,and ocean currents,which have destructive impacts on coastal regions.For a quantitative multi-hazard assessment of SSEs,this study introduced the concept of the storm surge event seawater-atmosphere system(SSE-SAS)and proposed the system energy equivalence(SEE)model from a systemic energy perspective.SEE was obtained by employing a parameterization approach,and the hazard index(HI)and the concept of most significant hazard(MSH)were adopted to evaluate the severity of SSE-SAS.SEE at five stations in the Shandong Peninsula was calculated from 2005 to 2019,and probability analysis and hazard assessment were further conducted.Results show that the SEE of SSE-SAS ranges from 0.029×10^(3) to 30.418×10^(3) J/m^(2),and it exhibits an insignificant decreasing trend from 2005 to 2019.The SEE of SSE-SAS in the west of the Shandong Peninsula is greater than that in the east.Moreover,storm waves,storm surges,and storm rainfall are the major contributors to SEE,which exhibit different spatial patterns and characters in different SSE-SAS types.The HI of SSE-SAS at five stations is no more than medium hazard level,with MSH at return periods of 2-to 4-year level.This study provides a new approach for quantifying multi-hazard SSEs,which offers scientific insights for regional multi-hazard risk reduction and mitigation efforts.
基金National Natural Science Foundation of China(No.52071306)the Natural Science Foundation of Shandong Province(No.ZR2019MEE050)the Natural Science Foundation of Zhejiang Province(No.LZ22E090003).
文摘The local time-stepping(LTS)algorithm is an adaptive method that adjusts the time step by selecting suitable intervals for different regions based on the spatial scale of each cell and water depth and flow velocity between cells.The method can be optimized by calculating the maximum power of two of the global time step increments in the domain,allowing the optimal time step to be approached throughout the grid.To verify the acceleration and accuracy of LTS in storm surge simulations,we developed a model to simulate astronomical storm surges along the southern coast of China.This model employs the shallow water equations as governing equations,numerical discretization using the finite volume method,and fluxes calculated by the Roe solver.By comparing the simulation results of the traditional global time-stepping algorithm with those of the LTS algorithm,we find that the latter fit the measured data better.Taking the calculation results of Typhoon Sally in 1996 as an example,we show that compared with the traditional global time-stepping algorithm,the LTS algorithm reduces computation time by 2.05 h and increases computation efficiency by 2.64 times while maintaining good accuracy.
基金National Natural Science Foundation of China,No.42201170Young Elite Scientists Sponsorship Program by CAST,No.2022QNRC001。
文摘Arid West Asia(AWA)is a critical hub of the Silk Road and one of the primary dust source regions in the Northern Hemisphere.Dust storms in AWA emitting substantial dust particles into the atmosphere,significantly influencing air quality,climate change and marine productivity.However,the variability of dust storm activity in this region during the Holocene,particularly its links to vegetation and hydroclimatic changes,remains debated,hindering our understanding of the interconnected dynamics between climate change and surface environments.This study reconstructs dust storm variations in AWA over the past 9000 years using geochemical analyses(trace elements,Sr-Nd isotopes)from a well-dated,high-resolution sediment core from the Almalou Peatland,located on the western Iranian Plateau.Our results reveal a decline in dust storm frequency from the early to mid-Holocene,a minimum occurrence during the mid-Holocene,and a significant increase in the late Holocene.Provenance analysis indicates that the primary dust sources were the arid regions of Mesopotamia,located upwind of the study area.A comparison with proxy records and paleoclimate models suggests an inverse relationship between dust storm activity and regional hydroclimatic and vegetation changes,along with a positive correlation with wind speeds.The concentration of dust storms during the wetter month of May highlights wind speed as a more critical driving factor.Moreover,given the dominant influence of the subtropical high on hydroclimatic conditions and wind speeds in AWA,we propose that this system is the key regulator of regional dust storm dynamics.Our findings provide new insights into the drivers of dust storm activity in AWA and hold implications for developing targeted dust storm management strategies.
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.
基金supported by the Yantai Science,Technology and Innovation Development Programme(Nos.2023 JCYJ094,2023JCYJ097)the Major Research Grant from the Natural Science Foundation of China(NSFC)(No.42330406)。
文摘To investigate the effect of typhoon path translation on storm surge augmentation,the storm surge during Typhoon 1909 Lekima in the East China Sea is simulated using Delft 3D.The model sets up three scenarios to analyze the path’s effect on storm surge in the Shandong Peninsula Sea by shifting the typhoon path to the east and west.Results show that the areas of maximum storm surge in each scenario are located on both sides of the typhoon path and shift along with its movement.When the typhoon path shifts eastward,the maximum storm surge intensifies at Zhifu Island station 8 hours earlier.Conversely,a westward shift in the typhoon track leads to a maximum storm surge increase at Shidao Island station 12 hours earlier.Other scenarios exhibit minimal deviation from the original route.Typhoons penetrating deep inland can induce substantial storm surges,with the most extensive surge area situated in the western part of the Shandong Peninsula.
基金funded by the National Natural Science Foundation of China(Grant Nos.42275140,42230612,91837310,41675041,and 92037000)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0104)。
文摘The North Pacific storm track(NPST)is a high-frequency area of extratropical cyclones and an important channel for water vapor and energy transfer between low and mid–high latitudes.Previous weather and dynamic studies in this region have made significant progress,but due to the lack of ocean surface rainfall observation data,there is a lack of statistical research on precipitation in this area.In this study,statistical research on the spatiotemporal distribution characteristics of NPST rainfall was conducted based on GPM DPR(Global Precipitation Measurement Dual-frequency Precipitation Radar)observation data and ERA5 atmospheric parameters,and analysis and explanations are provided based on the atmospheric parameters.The study found that,compared to low-pressure systems,pressure gradients have a greater impact on cyclone activity and rainfall distribution.This feature,along with the meridional distribution of high atmospheric water vapor in the North Pacific Ocean and low in the north,collectively leads to the offset of high-frequency rainfall areas relative to storm tracks.The distribution of sea surface temperatures in the North Pacific Ocean affects the zonal distribution of storm tracks,causing weather disturbances and precipitation along the storm tracks to exhibit a northward extension from west to east.This study deepens our understanding of the role of NPST in global-scale water vapor and energy balance,and is of great significance for improving the prediction accuracy of climate models with respect to rainfall generated by extratropical cyclones.
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supported by the Natural Science Foundation of Hebei Province(Nos.B2022407001 and D2021501004)the National Natural Science Foundation of China(No.42075107)the Fundamental Research Funds for the Central Universities(No.N2223011).
文摘An intense Asian dust storm invadedQinhuangdao,a coastal city ofNorth China on April 11-14,2023.We analyzed the bulk water-soluble inorganic ions(WSII)of PM_(10)and PM_(2.5)using an Ion Chromatograph and investigated individual particlemorphology and elemental composition using a scanning electron microscope coupled with energy dispersive X-ray.The results showed when the dust was directly transported to the sampling site from northwestern China(direct transport stages),the PM_(10)mass concentrations were high(675.0μg/m^(3))but the relative humidity(RH)was low.Total WSII were 19.54μg/m^(3)and 11.17μg/m^(3),accounting for 2.90%and 7.25%of the PM_(10)and PM_(2.5),respectively.In addition,the proportion of S-containing individual mineral dust was low(28.7%-35.3%).The results suggested there were limited secondary inorganic aerosol formation.However,when the dust was transported back to the sampling site across the Bohai Sea in the following days(reverse transport stages),both the PM_(10)mass concentrations(462.3μg/m^(3))and RH were high.Total WSII were 43.75μg/m^(3)and 18.71μg/m^(3),accounting for 9.62%and 14.45%of the total PM_(10)and PM_(2.5),respectively.The proportion of S-containing particles was 51.5%-72.5%.In addition,the concentration of NO_(3)^(−)was much higher than that of SO_(4)^(2−).The results suggested both the sulfate and nitrate formation occurred on coarse mineral dust but the nitrate formation exceeded sulfate formation.Interestingly,mostmineral dust,including Sirich particles contained Cl when they passed through the marine atmosphere.The results highlighted the heterogeneous reactions of dust varied in different transport stages.
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 by the National Natural Science Foundation of China(Nos.31971541 and 32201545).
文摘Extreme weather events pose an ever-greater threat to people,infrastructure,and nature.Forest ecosystems are highly sensitive to extreme cold events that can disrupt ecosystem functions,especially in montane regions.Ice storms can be particularly destructive,with rapid ice accretion causing tree branches to break,even snapping or uprooting entire trees.In March 2022,the Shennongjia forest in central China experienced severe ice storm conditions that severely damaged over 230,300ha.We utilized this opportunity to assess the vulnerability of different tree types(coniferous,deciduous,and evergreen broad-leaved)and stand compositions to damage resulting from ice glaze along an elevation gradient from 1,200 to 2,400m a.s.l.Among the 7,144 trees surveyed,10.1%suffered some extent of damage,which was most prolific in the middle elevation zone.While 96.8%of all damage occurred to deciduous broadleaved trees that dominated the forest community,the most severe damage(uprooting and lower trunk breakage)occurred to coniferous trees.The extent and severity of tree damage were moderated by forest composition,with secondary effects of forest structure and slope.Abiotic factors predominantly affected coniferous trees.We emphasize that more research and monitoring are needed to better understand the full impact of extreme weather events on forests,especially as the frequency and intensity of these events increases due to climate change.
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.
