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
The response of thermosphere density to geomagnetic storms is a complicated physical process.Multi-satellite joint observations at the same altitude but different local times(LTs)are important for understanding this p...The response of thermosphere density to geomagnetic storms is a complicated physical process.Multi-satellite joint observations at the same altitude but different local times(LTs)are important for understanding this process;however,until now such studies have hardly been done.In this report,we analyze in detail the thermosphere mass density response at 510 km during the April 23−24,2023 geomagnetic storm using data derived from the TM-1(TianMu-1)satellite constellation and Swarm-B satellites.The observations show that there were significant LT differences in the hemispheric asymmetry of the thermosphere mass density during the geomagnetic storm.Densities observed by satellite TM02 at nearly 11.3 and 23.3 LTs were larger in the northern hemisphere than in the southern.The TM04 dayside density observations appear to be almost symmetrical with respect to the equator,though southern hemisphere densities on the nightside were higher.Swarm-B data exhibit near-symmetry between the hemispheres.In addition,the mass density ratio results show that TM04 nightside observations,TM02 data,and Swarm-B data all clearly show stronger effects in the southern hemisphere,except for TM04 on the dayside,which suggest hemispheric near-symmetry.The South-North density enhancement differences in TM02 and TM04 on dayside can reach 130%,and Swarm-B data even achieve 180%difference.From the observations of all three satellites,large-scale traveling atmospheric disturbances(TADs)first appear at high latitudes and propagate to low latitudes,thereby disturbing the atmosphere above the equator and even into the opposite hemisphere.NRLMSISE00 model simulations were also performed on this geomagnetic storm.TADs are absent in the NRLMSISE00 simulations.The satellite data suggest that NRLMSISE00 significantly underestimates the magnitude of the density response of the thermosphere during geomagnetic storms,especially at high latitudes in both hemispheres.Therefore,use of the density simulation of NRLMSISE00 may lead to large errors in satellite drag calculations and orbit predictions.We suggest that the high temporal and spatial resolution of direct density observations by the TM-1 constellation satellites can provide an autonomous and reliable basis for correction and improvement of atmospheric models.展开更多
Climate change affects the activity of global and regional tropical cyclones(TCs).Among all TCs,typical super typhoons(STYs)are particularly devastating because they maintain their intensity when landing on the coast ...Climate change affects the activity of global and regional tropical cyclones(TCs).Among all TCs,typical super typhoons(STYs)are particularly devastating because they maintain their intensity when landing on the coast and thus cause casualties,economic losses,and environmental damage.Using a 3D tidal model,we reconstructed the typhoon(TY)wind field to simulate the storm surge induced by typical STYs.The TY activity was then analyzed using historical data.Results showed a downtrend of varying degrees in the annual frequency of STYs and TCs in the Western North Pacific(WNP)Basin,with a significant trend change observed for TCs from 1949 to 2021.A large difference in the interannual change in frequency was found between STYs and TCs in the WNP and Eastern China Sea(ECS).Along the coast of EC,the frequency of landfall TCs showed a weak downtrend,and the typical STYs showed reverse micro growth with peak activity in August.Zhejiang,Fujian,and Taiwan were highly vulnerable to the frontal hits of typical STYs.Affected by climate change,the average lifetime maximum intensity(LMI)locations and landfall locations of typical STYs in the ECS basin showed a significant poleward migration trend.In addition,the annual average LMI and accumulated cyclone energy showed an uptrend,indicating the increasing severity of the disaster risk.Affected by the typical STY activity in the ECS,the maximum storm surge area also showed poleward migration,and the coast of North China faced potential growth in high storm surge risks.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
Storm surge is often the marine disaster that poses the greatest threat to life and property in coastal areas.Accurate and timely issuance of storm surge warnings to take appropriate countermeasures is an important me...Storm surge is often the marine disaster that poses the greatest threat to life and property in coastal areas.Accurate and timely issuance of storm surge warnings to take appropriate countermeasures is an important means to reduce storm surge-related losses.Storm surge numerical models are important for storm surge forecasting.To further improve the performance of the storm surge forecast models,we developed a numerical storm surge forecast model based on an unstructured spherical centroidal Voronoi tessellation(SCVT)grid.The model is based on shallow water equations in vector-invariant form,and is discretized by Arakawa C grid.The SCVT grid can not only better describe the coastline information but also avoid rigid transitions,and it has a better global consistency by generating high-resolution grids in the key areas through transition refinement.In addition,the simulation speed of the model is accelerated by using the openACC-based GPU acceleration technology to meet the timeliness requirements of operational ensemble forecast.It only takes 37 s to simulate a day in the coastal waters of China.The newly developed storm surge model was applied to simulate typhoon-induced storm surges in the coastal waters of China.The hindcast experiments on the selected representative typhoon-induced storm surge processes indicate that the model can reasonably simulate the distribution characteristics of storm surges.The simulated maximum storm surges and their occurrence times are consistent with the observed data at the representative tide gauge stations,and the mean absolute errors are 3.5 cm and 0.6 h respectively,showing high accuracy and application prospects.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
The future inundation by storm surge on coastal areas are currently ill-defined.With increasing global sealevel due to climate change,the coastal flooding by storm surge is more and more frequently,especially in coast...The future inundation by storm surge on coastal areas are currently ill-defined.With increasing global sealevel due to climate change,the coastal flooding by storm surge is more and more frequently,especially in coastal lowland with land subsidence.Therefore,the risk assessment of such inundation for these areas is of great significance for the sustainable socio-economic development.In this paper,the authors use Elevation-Area method and Regional Ocean Model System(ROMS)model to assess the risk of the inundation of Bohai Bay by storm surge.The simulation results of Elevation-Area method show that either a 50-year or 100-year storm surge can inundate coastal areas exceeding 8000 km^(2);the numerical simulation results based on hydrodynamics,considering ground friction and duration of the storm surge high water,show that a 50-year or 100-year storm surge can only inundate an area of over 2000 km^(2),which is far less than 8000 km^(2);while,when taking into account the land subsidence and sea level rise,the very inundation range will rapidly increase by 2050 and 2100.The storm surge will greatly impact the coastal area within about 10-30 km of the Bohai Bay,in where almost all major coastal projects are located.The prompt response to flood disaster due to storm surge is urgently needed,for which five suggestions have been proposed based on the geological background of Bohai Bay.This study may offer insight into the development of the response and adaptive plans for flooding disasters caused by storm surge.展开更多
The Anta Storm Mecha Jacket is a rainproof and comfortable jacket launched by Anta and Donghua University.It is equipped with China's first self-developed high-performance waterproof and breathable material-Aerove...The Anta Storm Mecha Jacket is a rainproof and comfortable jacket launched by Anta and Donghua University.It is equipped with China's first self-developed high-performance waterproof and breathable material-Aerovent.This jacket not only has excellent waterproof performance,but also achieves a soft,breathable and comfortable wearing experience.After testing by an authoritative third-party organization,its waterproof and breathable performance is comparable to international brands.展开更多
The plasmapause locations determined from the Chang'e-3(CE-3) Extreme Ultraviolet Camera(EUVC) images and the auroral boundaries determined from the Defense Meteorological Satellite Program(DMSP) Special Sensor Ul...The plasmapause locations determined from the Chang'e-3(CE-3) Extreme Ultraviolet Camera(EUVC) images and the auroral boundaries determined from the Defense Meteorological Satellite Program(DMSP) Special Sensor Ultraviolet Spectrographic Imager(SSUSI) images are used to investigate the plasmaspheric evolutions during substorms. The most important finding is a nightside pointing plasmaspheric plume observed at 23:05 UT on 21 April 2014 under quiet solar wind and geomagnetic conditions, which drifted from the dusk sector. High correlations between the plasmapause evolutions and the auroral signatures exist during substorms. After substorm onset, the plasmapause erosion and the equatorward expansion of the auroral oval occur almost simultaneously in both MLT and UT, and then both the erosion and the expansion propagate westward and eastward. It is suggested that the plasmaspheric erosion and its MLT propagations are induced by the enhanced earthward plasma convection during substorm period, and the substorm dipolarization causes pitch-angle scattering of plasma sheet electrons and the resulting precipitation excites aurora emissions at the same time.展开更多
Exohiss is a low-frequency structureless whistler-mode emission potentially contributing to the precipitation loss of radiation belt electrons outside the plasmasphere. Exohiss is usually considered the plasmaspheric ...Exohiss is a low-frequency structureless whistler-mode emission potentially contributing to the precipitation loss of radiation belt electrons outside the plasmasphere. Exohiss is usually considered the plasmaspheric hiss leaked out of the dayside plasmapause.However, the evolution of exohiss after the leakage has not been fully understood. Here we report the prompt enhancements of exohiss waves following substorm injections observed by Van Allen Probes. Within several minutes, the energetic electron fluxes around 100 keV were enhanced by up to 5 times, accompanied by an up to 10-time increase of the exohiss wave power. These substorm-injected electrons are shown to produce a new peak of linear growth rate in the exohiss band(< 0.1 f_(ce)). The corresponding path-integrated growth rate of wave power within 10° latitude of the magnetic equatorial plane can reach 13.4, approximately explaining the observed enhancement of exohiss waves. These observations and simulations suggest that the substorm-injected energetic electrons could amplify the preexisting exohiss waves.展开更多
With conjunction observations of electromagnetic fields and plasma from Time History of Events and Macroscale Interactions during Substorm(THEMIS)in the near-Earth magnetotail,we investigate the spatial and temporal p...With conjunction observations of electromagnetic fields and plasma from Time History of Events and Macroscale Interactions during Substorm(THEMIS)in the near-Earth magnetotail,we investigate the spatial and temporal properties of substorm dipolarizations in the near-Earth plasma sheet(NEPS)during a substorm at 03:23 UT on 12 February 2008.Substorm dipolarizations with different features are detected by three near-Earth THEMIS probes(THA(P5),THD(P3)and THE(P4))in the magnetotail.In the current sheet with a large plasma beta value(β>2,whereβis the ratio of the plasma thermal pressure to the magnetic pressure),the dipolarization within the substorm onset region,(−10.4,2.8,−2.6)RE_gsm,has a large initial magnetic field elevation angle,θ>60°,θ=arctan(Bz/(Bx2+By2)1/2),and is accompanied by energetic ion(tens to hundred keV)dispersionless injection detected by THD(P3).This substorm onset dipolarization is characterized by Bx and By components around 0 nT with significant fluctuations.The Bz component increases sharply and its subsequent magnitude approaches the total magnetic field,Bt.The maximum value of the elevation angle approaches 85°during the later substorm expansion phase.In the NEPS withβ~1,the dipolarization outside the substorm onset region is characterized by a magnetic elevation angle with a small beginning value ofθ<45°and following multi-step enhancements during the substorm expansion phase.The maximum value of the elevation angle approaches to 70°during the later substorm expansion phase.Our observation results indicate that characteristics of dipolarization with a large beginning elevation angle within the substorm onset region provide a new indicator to identify substorm onset location.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
The Substorm Current Wedge (SCW) occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure curren...The Substorm Current Wedge (SCW) occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally was suggested to be the strong westward auroral electrojet (WEJ). However, the SCW-WEJ system has no viable generator current. Similarly, the asymmetric or Partial Ring Current (PRC) increases in strength during the growth phase, and is sometimes associated with an enhanced Region 2 field-aligned current (FAC) closing to the ionosphere, but specifics of that closure have been lacking. Here we present a tmifying picture which includes the SCW post- and pre-midnight (AM and PM, respectively) currents and a generator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotail magnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types of closed field line regions-stretched lines in the central part of the plasmasheet (SPS) and dipolar lines (DPS) between the low lati- tude boundary layer (LLBL) regions and the SPS. There is also an important plasmasheet transition region (TPS) in which the dipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which the midnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which be- comes part of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on the dawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the iono- sphere. These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriate locations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and the final upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originally proposed SCW.展开更多
Both theory and simulation have played important roles in defining and illuminating the key mechanisms involved in substorms.Basic theories of magnetic reconnection and of interchange and ballooning instabilities were...Both theory and simulation have played important roles in defining and illuminating the key mechanisms involved in substorms.Basic theories of magnetic reconnection and of interchange and ballooning instabilities were developed more than 50 years ago,and these plasma physical concepts have been central in discussions of substorm physics.A vast amount of research on reconnection,including both theoretical and computational studies,has helped provide a picture of how reconnection operates in the collisionless environment of the magnetosphere.Still,however,we do not fully understand how key microscale processes and large-scale dynamics work together to determine the location and rate of reconnection.While in the last twenty years,it has become clear that interchange processes are important for transporting plasma through the plasma sheet in the form of bursty bulk flows and substorm expansions,we still have not reached the point where simulations are able to realistically and defensibly represent all of the important aspects of the phenomenon.More than two decades ago it was suggested that the ballooning instability,the basic theory for which dates from the 1950s,may play an important role in substorms.Now the majority of experts agree that regions of the plasma sheet are often linearly unstable to ideal-MHD ballooning.However,it is also clear that kinetic effects introduce important modifications to the MHD stability criterion.It is still uncertain whether ballooning plays a leading role in substorms or has just a minor part.Among the different types of simulations that have been applied to the substorm problem,global MHD codes are unique in that,in a sense, they represent the entire global substorm phenomenon,including coupling to the solar wind and ionosphere, and the important mechanisms of reconnection,interchange,and ballooning.However,they have not yet progressed to the point where they can accurately represent the whole phenomenon,because grid-resolution problems limit the accuracy with which they can solve the equations of ideal MHD and the couphng to the ionosphere,and they cannot accurately represent small-scale processes that violate ideal MHD.展开更多
The characteristics of a strong aurora substorm observed at Antarctic Zhongshan station (magnetic latitude=74.5°) on 8 April, 1999, were discussed and analyzed. The developing steps of the aurora substorm that ha...The characteristics of a strong aurora substorm observed at Antarctic Zhongshan station (magnetic latitude=74.5°) on 8 April, 1999, were discussed and analyzed. The developing steps of the aurora substorm that happened in dusk time were almost the same with that of midnight aurora substorm. The averaged moving speed of the aurora arc toward pole area during the substorm expansion phase was about 3.0 km/s, westward-traveling surge speed was about 2.0 km/s. The extension from south to north in the substorm can cover 1100 km in distance.展开更多
This is a concise review of physics of the substorm in the magnetotail.It consists of two parts. The first part summarizes historical developments in the early days of the space age(1960-1975)when the basic concepts s...This is a concise review of physics of the substorm in the magnetotail.It consists of two parts. The first part summarizes historical developments in the early days of the space age(1960-1975)when the basic concepts such as magnetotail and reconnection were established and the leading model of the substorm was introduced.The second part is an overview of the research conducted in recent years(1995-2010)when very significant advances have been achieved in understanding the substorm physics by virtue of several major satellites missions that addressed the magnetotail physics intensively.展开更多
This paper gives a brief account of substorm modeling with different key elements or factors. The progress of our understanding of substorms consists of three chief stages during this century. Nine previous substorm m...This paper gives a brief account of substorm modeling with different key elements or factors. The progress of our understanding of substorms consists of three chief stages during this century. Nine previous substorm models are briefly recapitulated, and then a recent two neutral-points model by Prof. C.T. Russell is introduced. In order to test or to strengthen this new model, several correlated examples of meaningful data are duly given in this short paper.展开更多
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.
基金funded by the China Manned Space Program (Grant Y59003AC40)TM-1 Constellation Atmospheric Density Detector (Grant E3C1162110)
文摘The response of thermosphere density to geomagnetic storms is a complicated physical process.Multi-satellite joint observations at the same altitude but different local times(LTs)are important for understanding this process;however,until now such studies have hardly been done.In this report,we analyze in detail the thermosphere mass density response at 510 km during the April 23−24,2023 geomagnetic storm using data derived from the TM-1(TianMu-1)satellite constellation and Swarm-B satellites.The observations show that there were significant LT differences in the hemispheric asymmetry of the thermosphere mass density during the geomagnetic storm.Densities observed by satellite TM02 at nearly 11.3 and 23.3 LTs were larger in the northern hemisphere than in the southern.The TM04 dayside density observations appear to be almost symmetrical with respect to the equator,though southern hemisphere densities on the nightside were higher.Swarm-B data exhibit near-symmetry between the hemispheres.In addition,the mass density ratio results show that TM04 nightside observations,TM02 data,and Swarm-B data all clearly show stronger effects in the southern hemisphere,except for TM04 on the dayside,which suggest hemispheric near-symmetry.The South-North density enhancement differences in TM02 and TM04 on dayside can reach 130%,and Swarm-B data even achieve 180%difference.From the observations of all three satellites,large-scale traveling atmospheric disturbances(TADs)first appear at high latitudes and propagate to low latitudes,thereby disturbing the atmosphere above the equator and even into the opposite hemisphere.NRLMSISE00 model simulations were also performed on this geomagnetic storm.TADs are absent in the NRLMSISE00 simulations.The satellite data suggest that NRLMSISE00 significantly underestimates the magnitude of the density response of the thermosphere during geomagnetic storms,especially at high latitudes in both hemispheres.Therefore,use of the density simulation of NRLMSISE00 may lead to large errors in satellite drag calculations and orbit predictions.We suggest that the high temporal and spatial resolution of direct density observations by the TM-1 constellation satellites can provide an autonomous and reliable basis for correction and improvement of atmospheric models.
基金supported by four funds,including the National Key Research and Development Program of China(No.2022YFC3106102)the Marine Science and Technology Innovation Project of Jiangsu Province(Nos.JSZRH YKJ202105,JSZRHYKI202303)+1 种基金the Nantong Social and Livelihood Science and Technology Project(Nos.MS12022009,MS22022082,MS22022083)the Project on Excellent Post-Graduate Dissertation of Hohai University(No.422003470).
文摘Climate change affects the activity of global and regional tropical cyclones(TCs).Among all TCs,typical super typhoons(STYs)are particularly devastating because they maintain their intensity when landing on the coast and thus cause casualties,economic losses,and environmental damage.Using a 3D tidal model,we reconstructed the typhoon(TY)wind field to simulate the storm surge induced by typical STYs.The TY activity was then analyzed using historical data.Results showed a downtrend of varying degrees in the annual frequency of STYs and TCs in the Western North Pacific(WNP)Basin,with a significant trend change observed for TCs from 1949 to 2021.A large difference in the interannual change in frequency was found between STYs and TCs in the WNP and Eastern China Sea(ECS).Along the coast of EC,the frequency of landfall TCs showed a weak downtrend,and the typical STYs showed reverse micro growth with peak activity in August.Zhejiang,Fujian,and Taiwan were highly vulnerable to the frontal hits of typical STYs.Affected by climate change,the average lifetime maximum intensity(LMI)locations and landfall locations of typical STYs in the ECS basin showed a significant poleward migration trend.In addition,the annual average LMI and accumulated cyclone energy showed an uptrend,indicating the increasing severity of the disaster risk.Affected by the typical STY activity in the ECS,the maximum storm surge area also showed poleward migration,and the coast of North China faced potential growth in high storm surge risks.
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 Natural Science Foundation of China under contract No.42076214.
文摘Storm surge is often the marine disaster that poses the greatest threat to life and property in coastal areas.Accurate and timely issuance of storm surge warnings to take appropriate countermeasures is an important means to reduce storm surge-related losses.Storm surge numerical models are important for storm surge forecasting.To further improve the performance of the storm surge forecast models,we developed a numerical storm surge forecast model based on an unstructured spherical centroidal Voronoi tessellation(SCVT)grid.The model is based on shallow water equations in vector-invariant form,and is discretized by Arakawa C grid.The SCVT grid can not only better describe the coastline information but also avoid rigid transitions,and it has a better global consistency by generating high-resolution grids in the key areas through transition refinement.In addition,the simulation speed of the model is accelerated by using the openACC-based GPU acceleration technology to meet the timeliness requirements of operational ensemble forecast.It only takes 37 s to simulate a day in the coastal waters of China.The newly developed storm surge model was applied to simulate typhoon-induced storm surges in the coastal waters of China.The hindcast experiments on the selected representative typhoon-induced storm surge processes indicate that the model can reasonably simulate the distribution characteristics of storm surges.The simulated maximum storm surges and their occurrence times are consistent with the observed data at the representative tide gauge stations,and the mean absolute errors are 3.5 cm and 0.6 h respectively,showing high accuracy and application prospects.
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 National Natural Science Foundation of China(42293261)projects of the China Geological Survey(DD20230091,DD20189506,DD20211301)+1 种基金the 2024 Qinhuangdao City level Science and Technology Plan Self-Financing Project(Research on data processing methods for wave buoys in nearshore waters)the project of Hebei University of Environmental Engineering(GCZ202301)。
文摘The future inundation by storm surge on coastal areas are currently ill-defined.With increasing global sealevel due to climate change,the coastal flooding by storm surge is more and more frequently,especially in coastal lowland with land subsidence.Therefore,the risk assessment of such inundation for these areas is of great significance for the sustainable socio-economic development.In this paper,the authors use Elevation-Area method and Regional Ocean Model System(ROMS)model to assess the risk of the inundation of Bohai Bay by storm surge.The simulation results of Elevation-Area method show that either a 50-year or 100-year storm surge can inundate coastal areas exceeding 8000 km^(2);the numerical simulation results based on hydrodynamics,considering ground friction and duration of the storm surge high water,show that a 50-year or 100-year storm surge can only inundate an area of over 2000 km^(2),which is far less than 8000 km^(2);while,when taking into account the land subsidence and sea level rise,the very inundation range will rapidly increase by 2050 and 2100.The storm surge will greatly impact the coastal area within about 10-30 km of the Bohai Bay,in where almost all major coastal projects are located.The prompt response to flood disaster due to storm surge is urgently needed,for which five suggestions have been proposed based on the geological background of Bohai Bay.This study may offer insight into the development of the response and adaptive plans for flooding disasters caused by storm surge.
文摘The Anta Storm Mecha Jacket is a rainproof and comfortable jacket launched by Anta and Donghua University.It is equipped with China's first self-developed high-performance waterproof and breathable material-Aerovent.This jacket not only has excellent waterproof performance,but also achieves a soft,breathable and comfortable wearing experience.After testing by an authoritative third-party organization,its waterproof and breathable performance is comparable to international brands.
基金supported by National Natural Science Foundation of China (41674155 and 41274147)Youth Innovation Promotion Association of Chinese Academy of Sciences (No.2017258)Key Research Project of Chinese Academy of Sciences:Application Research on the Scientific Data from Chang’E-3 Mission (KGZD-EW-603)
文摘The plasmapause locations determined from the Chang'e-3(CE-3) Extreme Ultraviolet Camera(EUVC) images and the auroral boundaries determined from the Defense Meteorological Satellite Program(DMSP) Special Sensor Ultraviolet Spectrographic Imager(SSUSI) images are used to investigate the plasmaspheric evolutions during substorms. The most important finding is a nightside pointing plasmaspheric plume observed at 23:05 UT on 21 April 2014 under quiet solar wind and geomagnetic conditions, which drifted from the dusk sector. High correlations between the plasmapause evolutions and the auroral signatures exist during substorms. After substorm onset, the plasmapause erosion and the equatorward expansion of the auroral oval occur almost simultaneously in both MLT and UT, and then both the erosion and the expansion propagate westward and eastward. It is suggested that the plasmaspheric erosion and its MLT propagations are induced by the enhanced earthward plasma convection during substorm period, and the substorm dipolarization causes pitch-angle scattering of plasma sheet electrons and the resulting precipitation excites aurora emissions at the same time.
基金supported by National Natural Science Foundation of China grants 41631071, 41774170, 41274174, 41174125, 41131065, 41421063, 41231066 and 41304134Chinese Academy of Sciences grants KZCX2-EW-QN510 and KZZD-EW-01-4+2 种基金CAS Key Research Program of Frontier Sciences grant QYZDB-SSWDQC015National Key Basic Research Special Foundation of China Grant No. 2011CB811403Fundamental Research Funds for the Central Universities WK2080000077
文摘Exohiss is a low-frequency structureless whistler-mode emission potentially contributing to the precipitation loss of radiation belt electrons outside the plasmasphere. Exohiss is usually considered the plasmaspheric hiss leaked out of the dayside plasmapause.However, the evolution of exohiss after the leakage has not been fully understood. Here we report the prompt enhancements of exohiss waves following substorm injections observed by Van Allen Probes. Within several minutes, the energetic electron fluxes around 100 keV were enhanced by up to 5 times, accompanied by an up to 10-time increase of the exohiss wave power. These substorm-injected electrons are shown to produce a new peak of linear growth rate in the exohiss band(< 0.1 f_(ce)). The corresponding path-integrated growth rate of wave power within 10° latitude of the magnetic equatorial plane can reach 13.4, approximately explaining the observed enhancement of exohiss waves. These observations and simulations suggest that the substorm-injected energetic electrons could amplify the preexisting exohiss waves.
基金supported by the National Natural Science Foundation of China(NSFC)under grants 41731070,41674167,41574161the Strategic Pioneer Program on Space Science,Chinese Academy of Sciences,grants XDA15052500,XDA15350201 and XDA15011401the Specialized Research Fund for State Key Laboratories of China.
文摘With conjunction observations of electromagnetic fields and plasma from Time History of Events and Macroscale Interactions during Substorm(THEMIS)in the near-Earth magnetotail,we investigate the spatial and temporal properties of substorm dipolarizations in the near-Earth plasma sheet(NEPS)during a substorm at 03:23 UT on 12 February 2008.Substorm dipolarizations with different features are detected by three near-Earth THEMIS probes(THA(P5),THD(P3)and THE(P4))in the magnetotail.In the current sheet with a large plasma beta value(β>2,whereβis the ratio of the plasma thermal pressure to the magnetic pressure),the dipolarization within the substorm onset region,(−10.4,2.8,−2.6)RE_gsm,has a large initial magnetic field elevation angle,θ>60°,θ=arctan(Bz/(Bx2+By2)1/2),and is accompanied by energetic ion(tens to hundred keV)dispersionless injection detected by THD(P3).This substorm onset dipolarization is characterized by Bx and By components around 0 nT with significant fluctuations.The Bz component increases sharply and its subsequent magnitude approaches the total magnetic field,Bt.The maximum value of the elevation angle approaches 85°during the later substorm expansion phase.In the NEPS withβ~1,the dipolarization outside the substorm onset region is characterized by a magnetic elevation angle with a small beginning value ofθ<45°and following multi-step enhancements during the substorm expansion phase.The maximum value of the elevation angle approaches to 70°during the later substorm expansion phase.Our observation results indicate that characteristics of dipolarization with a large beginning elevation angle within the substorm onset region provide a new indicator to identify substorm onset location.
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.
文摘The Substorm Current Wedge (SCW) occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally was suggested to be the strong westward auroral electrojet (WEJ). However, the SCW-WEJ system has no viable generator current. Similarly, the asymmetric or Partial Ring Current (PRC) increases in strength during the growth phase, and is sometimes associated with an enhanced Region 2 field-aligned current (FAC) closing to the ionosphere, but specifics of that closure have been lacking. Here we present a tmifying picture which includes the SCW post- and pre-midnight (AM and PM, respectively) currents and a generator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotail magnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types of closed field line regions-stretched lines in the central part of the plasmasheet (SPS) and dipolar lines (DPS) between the low lati- tude boundary layer (LLBL) regions and the SPS. There is also an important plasmasheet transition region (TPS) in which the dipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which the midnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which be- comes part of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on the dawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the iono- sphere. These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriate locations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and the final upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originally proposed SCW.
基金supported by the NASA Heliospheric Theory Program under grant NNX08AI55G
文摘Both theory and simulation have played important roles in defining and illuminating the key mechanisms involved in substorms.Basic theories of magnetic reconnection and of interchange and ballooning instabilities were developed more than 50 years ago,and these plasma physical concepts have been central in discussions of substorm physics.A vast amount of research on reconnection,including both theoretical and computational studies,has helped provide a picture of how reconnection operates in the collisionless environment of the magnetosphere.Still,however,we do not fully understand how key microscale processes and large-scale dynamics work together to determine the location and rate of reconnection.While in the last twenty years,it has become clear that interchange processes are important for transporting plasma through the plasma sheet in the form of bursty bulk flows and substorm expansions,we still have not reached the point where simulations are able to realistically and defensibly represent all of the important aspects of the phenomenon.More than two decades ago it was suggested that the ballooning instability,the basic theory for which dates from the 1950s,may play an important role in substorms.Now the majority of experts agree that regions of the plasma sheet are often linearly unstable to ideal-MHD ballooning.However,it is also clear that kinetic effects introduce important modifications to the MHD stability criterion.It is still uncertain whether ballooning plays a leading role in substorms or has just a minor part.Among the different types of simulations that have been applied to the substorm problem,global MHD codes are unique in that,in a sense, they represent the entire global substorm phenomenon,including coupling to the solar wind and ionosphere, and the important mechanisms of reconnection,interchange,and ballooning.However,they have not yet progressed to the point where they can accurately represent the whole phenomenon,because grid-resolution problems limit the accuracy with which they can solve the equations of ideal MHD and the couphng to the ionosphere,and they cannot accurately represent small-scale processes that violate ideal MHD.
基金Sup POrted by the National Natural Science FOundation of China(4 96 3416 0 )
文摘The characteristics of a strong aurora substorm observed at Antarctic Zhongshan station (magnetic latitude=74.5°) on 8 April, 1999, were discussed and analyzed. The developing steps of the aurora substorm that happened in dusk time were almost the same with that of midnight aurora substorm. The averaged moving speed of the aurora arc toward pole area during the substorm expansion phase was about 3.0 km/s, westward-traveling surge speed was about 2.0 km/s. The extension from south to north in the substorm can cover 1100 km in distance.
文摘This is a concise review of physics of the substorm in the magnetotail.It consists of two parts. The first part summarizes historical developments in the early days of the space age(1960-1975)when the basic concepts such as magnetotail and reconnection were established and the leading model of the substorm was introduced.The second part is an overview of the research conducted in recent years(1995-2010)when very significant advances have been achieved in understanding the substorm physics by virtue of several major satellites missions that addressed the magnetotail physics intensively.
文摘This paper gives a brief account of substorm modeling with different key elements or factors. The progress of our understanding of substorms consists of three chief stages during this century. Nine previous substorm models are briefly recapitulated, and then a recent two neutral-points model by Prof. C.T. Russell is introduced. In order to test or to strengthen this new model, several correlated examples of meaningful data are duly given in this short paper.