This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches,in relation to the interplanetary magnetic field(IMF)and ionospheric convection geometry.A total of 11,946 patch events were ide...This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches,in relation to the interplanetary magnetic field(IMF)and ionospheric convection geometry.A total of 11,946 patch events were identified by Defense Meteorological Satellite Program(DMSP)F16 during the years 2011 to 2022.A temperature ratio of ion/electron temperature(T_(i)/T_(e))<0.68 is recommended to define a hot patch in the Southern Hemisphere,otherwise it is defined as a cold patch.The cold and hot patches have different dependencies on IMF clock angle,while their dependencies on IMF cone angle are similar.Both cold and hot patches appear most often on the duskside,and the distribution of cold patches gradually decreases from the dayside to the nightside,while hot patches have a higher occurrence rate near 14 and 21 magnetic local time(MLT).Moreover,we compared the key plasma characteristics of polar cap cold and hot patches in the Southern and Northern Hemispheres.The intensity of the duskside upward field-aligned current of patches in the Southern Hemisphere(SH)is stronger than that in the Northern Hemisphere(SH),which may be due to the discrepancy in conductivities between the two hemispheres,caused by the tilted dipole.In both hemispheres,the downward soft-electron energy flux of the dawnside patches is significantly greater than that of the duskside patches.展开更多
The snow density is a fundamental variable of the snow physical evolution processes,which can reflect the snowpack condition due to the thermal and gravitational compaction.Snow density is a bridge to transfer snow de...The snow density is a fundamental variable of the snow physical evolution processes,which can reflect the snowpack condition due to the thermal and gravitational compaction.Snow density is a bridge to transfer snow depth to snow water equivalent(SWE)for the snow water resources research.Therefore,it is important to understand the spatiotemporal distribution of snow density for the appropriate estimation of SWE.In this study,in situ snow densities from more than 6,000 stations in the Northern Hemisphere were used to analyze the spatial and temporal variations in snow density.The results displayed that snow density varied spatially and temporally in the Northern Hemisphere,with range of below 0.1 to over 0.4 g/cm^(3).The average snow densities in the mountainous regions of western North America,southeastern Canada,and Europe range from approximately 0.24 to 0.26 g/cm^(3),which is significantly greater than the values of 0.16–0.17 g/cm^(3)observed in Siberia,central Canada,the Great Plains of the United States,and China.The seasonal growth rates also present large spatial heterogeneity.The rates are over 0.024 g/cm^(3)per month in Southeastern Canada,the west mountain of North America and Europe,approximately 0.017 g/cm^(3)per month in Siberia,much larger than approximately 0.004 g/cm^(3)per month in other regions.Snow cover duration is a critical factor to determine the snow density.This study endorses the small snow density in China based on meteorological station observations,which results from that the meteorological stations are dominantly distributed in plain areas with relative short snow cover duration and shallow snow.展开更多
In this study,we analyze the impact of the May 2024 geomagnetic storm on the thermospheric mass density by using TianMu-1 constellation satellite(TM02,TM06,TM07,TM11,TM15)observations.These observations reveal intense...In this study,we analyze the impact of the May 2024 geomagnetic storm on the thermospheric mass density by using TianMu-1 constellation satellite(TM02,TM06,TM07,TM11,TM15)observations.These observations reveal intense large-scale traveling atmospheric disturbances(TADs)originating at high latitudes and propagating equatorward.Observations by TM02 captured the evolution of a TAD structure:An initial amplitude of~3.89×10^(-12)kg/m^(3)at hundred-kilometer scale subsequently intensified to 4.78×10^(-12)kg/m^(3),with the spatial extent expanding to the thousand-kilometer level.Significant hemispheric asymmetry was observed:the absolute density was higher predominantly in the northern hemisphere(TM02,TM06,TM07,TM11),whereas the difference in the relative density consistently showed greater enhancements in the southern hemisphere across all satellites,with the maximum north-south density differences exceeding 195%-640%above 60°latitude.In conjunction with SuperDARN(Super Dual Auroral Radar Network)observations,this striking hemispheric asymmetry can likely be attributed to disparities in plasma convection patterns between the two hemispheres.Furthermore,density perturbation characteristics exhibited strong local time(LT)dependence:Near noon(~10.7 LT,TM02 descending),the northern hemisphere onset preceded the southern onset.Conversely,near dusk(~17.6 LT,TM15 descending),the southern onset led the northern onset by approximately 3 hours.Ascending orbits(TM02,TM06,TM07,TM15)typically yielded larger global density enhancements compared with smaller southern-confined enhancements during descending orbits.Satellite TM11 showed comparable perturbations in both ascending and descending orbits.By leveraging its unique orbital architecture,the TianMu-1 constellation enables global near-simultaneous multi-LT sampling,providing a robust data foundation for both scientific research and engineering applications.展开更多
This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid-high latitudes on East Asian climate within the framework of a“coupled oceanic-atmospheric(lan...This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid-high latitudes on East Asian climate within the framework of a“coupled oceanic-atmospheric(land-atmospheric or seaice-atmospheric)bridge”and“chain coupled bridge”.Four major categories of pathways are concentrated upon,as follows:Pathway A—from North Atlantic to East Asia;Pathway B—from the North Pacific to East Asia;Pathway C—from the Arctic to East Asia;and Pathway D—the synergistic effects of the mid-high latitudes and tropics.In addition,definitions of the terms“combined effect”,“synergistic effect”and“antagonistic effect”of two or more factors of influence or processes and their criteria are introduced,so as to objectively investigate those effects in future research.展开更多
A model of focal cerebral ischemic infarction was established in dogs through middle cerebral artery occlusion of the right side.Thirty minutes after occlusion,models were injected with nerve growth factor adjacent to...A model of focal cerebral ischemic infarction was established in dogs through middle cerebral artery occlusion of the right side.Thirty minutes after occlusion,models were injected with nerve growth factor adjacent to the infarct locus.The therapeutic effect of nerve growth factor against cerebral infarction was assessed using the hemisphere anomalous volume ratio,a quantitative index of diffusion-weighted MRI.At 6 hours,24 hours,7 days and 3 months after modeling,the hemisphere anomalous volume ratio was significantly reduced after treatment with nerve growth factor. Hematoxylin-eosin staining,immunohistochemistry,electron microscopy and neurological function scores showed that infarct defects were slightly reduced and neurological function significantly improved after nerve growth factor treatment.This result was consistent with diffusion-weighted MRI measurements.Experimental findings indicate that nerve growth factor can protect against cerebral infarction,and that the hemisphere anomalous volume ratio of diffusion-weighted MRI can be used to evaluate the therapeutic effect.展开更多
Explosive cyclones(ECs)over two basins in the Northern Hemisphere(20°-90°N)from January 1979 to December2016 are investigated using ERA-Interim and Optimum Interpolation Sea Surface Temperature(OISST)data.Th...Explosive cyclones(ECs)over two basins in the Northern Hemisphere(20°-90°N)from January 1979 to December2016 are investigated using ERA-Interim and Optimum Interpolation Sea Surface Temperature(OISST)data.The classical definition of an EC is modified considering not only the rapid drop of the central sea level pressure of the cyclone,but also the strong wind speed at the height of 10 m in which maximum wind speeds greater than 17.2 m s^-1are included.According to the locations of the northern Atlantic and northern Pacific,the whole Northern Hemisphere is divided into the"A region"(20°-90°N,90°W-90°E)and"P region"(20°-90°N,90°E-90°W).Over both the A and P regions,the climatological features of ECs,such as their spatial distribution,intensity,seasonal variation,interannual variation,and moving tracks,are documented.展开更多
Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to expl...Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect （MEE） as independent variables and timberline elevation as dependent variable to develop a ternary linear regression meteorological data released by WorldClim and model. Continentality is calculated using the mountain base elevation （as a proxy of mass elevation effect） is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination （R2） of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02% （p=0.000）, 6.04% （p=0.000） and 48.94% （p=0.000）, respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude dif- fers in different regions, e.g., 50.49% （p=0.000） in North America, 48.73% （p=0.000） in the eastern Eurasia, and 43.6% （p=0.000） in the western Eurasia, but it is usually very high.展开更多
The long-term relationship between the tree-ring-reconstructed annual precipitation in northeastern Mongolia （PRM） and the Northern Hemisphere Zonal Circulation （NHZC）, defined as the normalized zonal mean sea-lev...The long-term relationship between the tree-ring-reconstructed annual precipitation in northeastern Mongolia （PRM） and the Northern Hemisphere Zonal Circulation （NHZC）, defined as the normalized zonal mean sea-level pressure at 60°N in May-June-July, is examined in this study. A significant correlation coefficient （0.31） was found between the NHZC indices and PRM based on the dataset for the period of 1872-1995. The mechanisms responsible for the relationship are discussed through analyses of the atmospheric general circulation variability associated with NHZC. It follows that NHZC-related atmospheric circulation variability provides an anomalous southeast flow from the ocean to Northeast Mongolia （northwest flow from Northeast Mongolia to the ocean） in the middle and low troposphere in positive （negative） phase of NHZC, resulting in more （less） water vapor transport to the target region and more （less） precipitation in Northeast Mongolia.展开更多
基金supported by the National Natural Science Foundation of China(Grants 42325404,42120104003,42204164,42474219 and U22A2006)the Chinese Meridian Project,the International Partnership Program of Chinese Academy of Sciences(Grant 183311KYSB20200003)+7 种基金Shandong Provincial Natural Science Foundation(Grants ZR2022QD077,ZR2022MD034)the Stable-Support Scientific Project of China Research Institute of Radiowave Propagation(Grant A132312191)the foundation of the National Key Laboratory of Electromagnetic Environment(Grant 6142403180204)the Chongqing Natural Science Foundation(Grants cstc2021ycjh-bgzxm0072,CSTB2023NSCQ-LZX0082)National Program on Key Basic Research Project(Grant 2022173-SD-1)The work in Norway is supported by the Research Council of Norway Grant 326039Work at UCLA has been supported by NSF grant AGS-2055192This research was supported by the International Space Science Institute(ISSI)in Bern and Beijing,through ISSI International Team project#511(Multi-Scale Magnetosphere-Ionosphere-Thermosphere Interaction).
文摘This paper is a statistical survey of Southern Hemisphere cold and hot polar cap patches,in relation to the interplanetary magnetic field(IMF)and ionospheric convection geometry.A total of 11,946 patch events were identified by Defense Meteorological Satellite Program(DMSP)F16 during the years 2011 to 2022.A temperature ratio of ion/electron temperature(T_(i)/T_(e))<0.68 is recommended to define a hot patch in the Southern Hemisphere,otherwise it is defined as a cold patch.The cold and hot patches have different dependencies on IMF clock angle,while their dependencies on IMF cone angle are similar.Both cold and hot patches appear most often on the duskside,and the distribution of cold patches gradually decreases from the dayside to the nightside,while hot patches have a higher occurrence rate near 14 and 21 magnetic local time(MLT).Moreover,we compared the key plasma characteristics of polar cap cold and hot patches in the Southern and Northern Hemispheres.The intensity of the duskside upward field-aligned current of patches in the Southern Hemisphere(SH)is stronger than that in the Northern Hemisphere(SH),which may be due to the discrepancy in conductivities between the two hemispheres,caused by the tilted dipole.In both hemispheres,the downward soft-electron energy flux of the dawnside patches is significantly greater than that of the duskside patches.
基金funded by the National Natural Science Foundation of China(Grant Nos:42125604&42171143)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0201)。
文摘The snow density is a fundamental variable of the snow physical evolution processes,which can reflect the snowpack condition due to the thermal and gravitational compaction.Snow density is a bridge to transfer snow depth to snow water equivalent(SWE)for the snow water resources research.Therefore,it is important to understand the spatiotemporal distribution of snow density for the appropriate estimation of SWE.In this study,in situ snow densities from more than 6,000 stations in the Northern Hemisphere were used to analyze the spatial and temporal variations in snow density.The results displayed that snow density varied spatially and temporally in the Northern Hemisphere,with range of below 0.1 to over 0.4 g/cm^(3).The average snow densities in the mountainous regions of western North America,southeastern Canada,and Europe range from approximately 0.24 to 0.26 g/cm^(3),which is significantly greater than the values of 0.16–0.17 g/cm^(3)observed in Siberia,central Canada,the Great Plains of the United States,and China.The seasonal growth rates also present large spatial heterogeneity.The rates are over 0.024 g/cm^(3)per month in Southeastern Canada,the west mountain of North America and Europe,approximately 0.017 g/cm^(3)per month in Siberia,much larger than approximately 0.004 g/cm^(3)per month in other regions.Snow cover duration is a critical factor to determine the snow density.This study endorses the small snow density in China based on meteorological station observations,which results from that the meteorological stations are dominantly distributed in plain areas with relative short snow cover duration and shallow snow.
基金the National Space Science Center (NSSC) of the Chinese Academy of Sciences for full support of this research workfunded by the Tian Mu-1 Constellation Atmospheric Density Detector (Grant No. E3C1162110)
文摘In this study,we analyze the impact of the May 2024 geomagnetic storm on the thermospheric mass density by using TianMu-1 constellation satellite(TM02,TM06,TM07,TM11,TM15)observations.These observations reveal intense large-scale traveling atmospheric disturbances(TADs)originating at high latitudes and propagating equatorward.Observations by TM02 captured the evolution of a TAD structure:An initial amplitude of~3.89×10^(-12)kg/m^(3)at hundred-kilometer scale subsequently intensified to 4.78×10^(-12)kg/m^(3),with the spatial extent expanding to the thousand-kilometer level.Significant hemispheric asymmetry was observed:the absolute density was higher predominantly in the northern hemisphere(TM02,TM06,TM07,TM11),whereas the difference in the relative density consistently showed greater enhancements in the southern hemisphere across all satellites,with the maximum north-south density differences exceeding 195%-640%above 60°latitude.In conjunction with SuperDARN(Super Dual Auroral Radar Network)observations,this striking hemispheric asymmetry can likely be attributed to disparities in plasma convection patterns between the two hemispheres.Furthermore,density perturbation characteristics exhibited strong local time(LT)dependence:Near noon(~10.7 LT,TM02 descending),the northern hemisphere onset preceded the southern onset.Conversely,near dusk(~17.6 LT,TM15 descending),the southern onset led the northern onset by approximately 3 hours.Ascending orbits(TM02,TM06,TM07,TM15)typically yielded larger global density enhancements compared with smaller southern-confined enhancements during descending orbits.Satellite TM11 showed comparable perturbations in both ascending and descending orbits.By leveraging its unique orbital architecture,the TianMu-1 constellation enables global near-simultaneous multi-LT sampling,providing a robust data foundation for both scientific research and engineering applications.
基金supported by the National Natural Science Foundation of China(41790474)the State Oceanic Administration International Cooperation Program on Global Change and Air–Sea Interactions(GASI-IPOVAI-03)
文摘This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid-high latitudes on East Asian climate within the framework of a“coupled oceanic-atmospheric(land-atmospheric or seaice-atmospheric)bridge”and“chain coupled bridge”.Four major categories of pathways are concentrated upon,as follows:Pathway A—from North Atlantic to East Asia;Pathway B—from the North Pacific to East Asia;Pathway C—from the Arctic to East Asia;and Pathway D—the synergistic effects of the mid-high latitudes and tropics.In addition,definitions of the terms“combined effect”,“synergistic effect”and“antagonistic effect”of two or more factors of influence or processes and their criteria are introduced,so as to objectively investigate those effects in future research.
基金supported by the Hebei Provincial Medical Science Research Key Youth Project,No.20100078
文摘A model of focal cerebral ischemic infarction was established in dogs through middle cerebral artery occlusion of the right side.Thirty minutes after occlusion,models were injected with nerve growth factor adjacent to the infarct locus.The therapeutic effect of nerve growth factor against cerebral infarction was assessed using the hemisphere anomalous volume ratio,a quantitative index of diffusion-weighted MRI.At 6 hours,24 hours,7 days and 3 months after modeling,the hemisphere anomalous volume ratio was significantly reduced after treatment with nerve growth factor. Hematoxylin-eosin staining,immunohistochemistry,electron microscopy and neurological function scores showed that infarct defects were slightly reduced and neurological function significantly improved after nerve growth factor treatment.This result was consistent with diffusion-weighted MRI measurements.Experimental findings indicate that nerve growth factor can protect against cerebral infarction,and that the hemisphere anomalous volume ratio of diffusion-weighted MRI can be used to evaluate the therapeutic effect.
基金the National Natural Science Foundation of China for financial support (Grant Nos. 41775042 and 41275049)
文摘Explosive cyclones(ECs)over two basins in the Northern Hemisphere(20°-90°N)from January 1979 to December2016 are investigated using ERA-Interim and Optimum Interpolation Sea Surface Temperature(OISST)data.The classical definition of an EC is modified considering not only the rapid drop of the central sea level pressure of the cyclone,but also the strong wind speed at the height of 10 m in which maximum wind speeds greater than 17.2 m s^-1are included.According to the locations of the northern Atlantic and northern Pacific,the whole Northern Hemisphere is divided into the"A region"(20°-90°N,90°W-90°E)and"P region"(20°-90°N,90°E-90°W).Over both the A and P regions,the climatological features of ECs,such as their spatial distribution,intensity,seasonal variation,interannual variation,and moving tracks,are documented.
基金National Natural Science Foundation of China,No.41030528No.40971064
文摘Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect （MEE） as independent variables and timberline elevation as dependent variable to develop a ternary linear regression meteorological data released by WorldClim and model. Continentality is calculated using the mountain base elevation （as a proxy of mass elevation effect） is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination （R2） of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02% （p=0.000）, 6.04% （p=0.000） and 48.94% （p=0.000）, respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude dif- fers in different regions, e.g., 50.49% （p=0.000） in North America, 48.73% （p=0.000） in the eastern Eurasia, and 43.6% （p=0.000） in the western Eurasia, but it is usually very high.
基金supported by the Chinese Academy of Sciences key program under Grant KZCX3-SW-221the National Natural Science Foundation of China under Grant Nos.40620130113 and 40475037.
文摘The long-term relationship between the tree-ring-reconstructed annual precipitation in northeastern Mongolia （PRM） and the Northern Hemisphere Zonal Circulation （NHZC）, defined as the normalized zonal mean sea-level pressure at 60°N in May-June-July, is examined in this study. A significant correlation coefficient （0.31） was found between the NHZC indices and PRM based on the dataset for the period of 1872-1995. The mechanisms responsible for the relationship are discussed through analyses of the atmospheric general circulation variability associated with NHZC. It follows that NHZC-related atmospheric circulation variability provides an anomalous southeast flow from the ocean to Northeast Mongolia （northwest flow from Northeast Mongolia to the ocean） in the middle and low troposphere in positive （negative） phase of NHZC, resulting in more （less） water vapor transport to the target region and more （less） precipitation in Northeast Mongolia.
