Based on the ERA reanalysis winds data, the multi-time scale variations of Somali jet are analyzed synthetically. The jet's influences on rainfall in China on interannual, interdecadal and sub-monthly scales are a...Based on the ERA reanalysis winds data, the multi-time scale variations of Somali jet are analyzed synthetically. The jet's influences on rainfall in China on interannual, interdecadal and sub-monthly scales are also studied using correlation and composite analyses. The results demonstrate that the interdecadal variations of the jet are significant.The Somali jet became weaker in the 1960 s and became the weakest in the early 1970 s before enhancing slowly in the late 1970 s. Moreover, the relation between the Somali jet and summer precipitation in China is close, but varies on different timescales. Preliminary analysis shows that the intensity variations in May and June during the early days of establishment are well correlated with summer precipitation in China. The Somali jet intensity on the interdecadal scale is closely related with interdecadal variations of the precipitation in China. Regardless of leading or contemporaneous correlation, the correlations between the Somali jet intensity and the rainfall in northern and southern China show obvious interdecadal variations. Moreover, the link between the anomalies of the jet intensity in May-August and precipitation evolution on synoptic scale in China is further studied. China has more rainfall with positive anomalies of the Somali jet but less rainfall with negative anomalies during the active period of the jet. The influence of positive Somali jet anomalies on China precipitation is more evident.展开更多
Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and ...Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and reanalysis data(MERRA-2)from March 2007 to February 2015(eight years).The horizontal distribution reveals lower cirrus fraction values in the northern SCS and higher values in the southern region,with minima observed in March and April and maxima sequentially occurring in August(northern SCS,NSCS),September(middle SCS,MSCS),and December(southern SCS,SSCS).Vertically,the cirrus fraction peaks in summer and reaches its lowest levels in spring.Opaque cirrus dominates during summer in the NSCS and MSCS,comprising 53.6%and 55.9%,respectively,while the SSCS exhibits a higher frequency of opaque cirrus relative to other cloud types.Subvisible cirrus clouds have the lowest frequency year-round,whereas thin cirrus is most prominent in winter in the NSCS(46.3%)and in spring in the MSCS(45.3%).A case study from September 2021 further explores the influence of ice crystal habits on brightness temperature(BT)over the SCS.Simulations utilizing five ice crystal shapes from the ARTS DDA(Atmospheric Radiative Transfer Simulator Discrete Dipole Approximation)database and the RTTOV 12.4 radiative transfer model reveal that the 8-column-aggregate shape best represents BT in the NSCS and SSCS,while the large-block-aggregate shape performs better in the SSCS.展开更多
The National Geophysical Data Center(NGDC)of the United States has collected aeromagnetic data for input into a series of geomagnetic models to improve model resolution;however,in the Tibetan Plateau region,ground-bas...The National Geophysical Data Center(NGDC)of the United States has collected aeromagnetic data for input into a series of geomagnetic models to improve model resolution;however,in the Tibetan Plateau region,ground-based observations remain insufficient to clearly reflect the characteristics of the region’s lithospheric magnetism.In this study,we evaluate the lithospheric magnetism of the Tibetan Plateau by using a 3D surface spline model based on observations from>200 newly constructed repeat stations(portable stations)to determine the spatial distribution of plateau geomagnetism,as well as its correlation with the tectonic features of the region.We analyze the relationships between M≥5 earthquakes and lithospheric magnetic field variations on the Tibetan Plateau and identify regions susceptible to strong earthquakes.We compare the geomagnetic results with those from an enhanced magnetic model(EMM2015)developed by the NGDC and provide insights into improving lithospheric magnetic field calculations in the Tibetan Plateau region.Further research reveals that these magnetic anomalies exhibit distinct differences from the magnetic-seismic correlation mechanisms observed in other tectonic settings;here,they are governed primarily by the combined effects of compressional magnetism,thermal magnetism,and deep thermal stress.This study provides new evidence of geomagnetic anomalies on the Tibetan Plateau,interprets them physically,and demonstrates their potential for identifying seismic hazard zones on the Plateau.展开更多
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive degeneration of upper and lower motor neurons in the brainstem and spinal cord,leading to muscle weakness,para...Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive degeneration of upper and lower motor neurons in the brainstem and spinal cord,leading to muscle weakness,paralysis,and respiratory failure (Morgan and Orrell,2016).展开更多
Halocarbons play a vital role in ozone depletion and global warming,and are regulated by the Montreal Protocol(MP)and its amendments.China has been identified as an important contributor to the halocarbon emissions,bu...Halocarbons play a vital role in ozone depletion and global warming,and are regulated by the Montreal Protocol(MP)and its amendments.China has been identified as an important contributor to the halocarbon emissions,but the regional sources of halocarbons in China are not yet well comprehended.To investigate the characteristics,emissions,and source profiles,this study conducted a field campaign in Xiamen,a coastal city in southeastern China.Higher enhancements were found in the unregulated halocarbons(CH_(3)Cl,CH_(2)Cl_(2),CHCl_(3))than in the MP eliminated species(CCl_(4),CH_(3)Br)and theMP controlled species(HCFCs,HFCs).Many of the measured halocarbons varied seasonally and regionally,depending on the anthropogenic sources and atmospheric transport.Backward trajectory analysis showed that the air masses from inland were polluted over Shandong,Hebei,and northern Fujian in the cold season,while the air masses fromthe sea in the warm season were clean.Different air masses in two seasons were associated with the halocarbon patterns in the study area.Industrial activities,especially solvent usage,were the primary sources of halocarbons.The emission hot spots in Fujian Province were concentrated in Sanming,Fuzhou,and Xiamen,and the unregulated halocarbons made the largest contribution.This study provides an insight for a deep understanding of the characteristics and potential sources of halocarbons,and for strengthened management of halocarbons in China.展开更多
Southerly moisture surges over the central South China Sea(SCS)are characterized by the strengthening of lowlevel southerlies that transport moisture northward from the Pacific or Indian Oceans to South China.These su...Southerly moisture surges over the central South China Sea(SCS)are characterized by the strengthening of lowlevel southerlies that transport moisture northward from the Pacific or Indian Oceans to South China.These surge events typically occur for days in the early-summer season(from April to June)and can lead to heavy rains in South China.This study categorizes surge events into three types of flow patterns and examines their multiscale variations and impacts on rainfall.The first type occurs mainly in April,with the southeasterlies enhanced by a deepening trough in South China and the western Pacific subtropical high established over the SCS.The second type of surge events mostly appears in June,featuring the prevailing southwesterlies of summer monsoon from the Indian Ocean during the active phases of intraseasonal oscillations.Most surge events exhibit semi-diurnal variations with morning and afternoon peaks of northward moisture fluxes.Specifically,the first type features a dominant afternoon peak,while the second type shows a dominant early-morning peak,which is induced by thermal contrast between the Indochina Peninsula and the SCS.In general,the surge events enhance moisture convergence and increase rainfall downstream in South China,but they show some regional differences.The second type strengthens moisture convergence and rainfall in coastal regions with a morning peak.In contrast,the first type enhances inland rainfall with a morning peak,while moisture divergence dominates coastal regions.The third type of surge events denotes transitional conditions between the first two types,in terms of atmospheric circulations,diurnal cycles,and rainfall patterns.These results highlight a diversity of regional moisture surges and related rainfall ranging from diurnal to sub-seasonal scales.展开更多
Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress,while hexaploid wild Camellia oleifera shows strong freezing tolerance.As a valuable genetic resource of woody oil crop C.oleifera,wil...Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress,while hexaploid wild Camellia oleifera shows strong freezing tolerance.As a valuable genetic resource of woody oil crop C.oleifera,wild C.oleifera can serve as a case for studying the molecular bases of adaptive evolution to freezing stress.Here,47 wild C.oleifera from 11 natural distribution sites in China and 4 relative species of C.oleifera were selected for genome sequencing.“Min Temperature of Coldest Month”(BIO6)had the highest comprehensive contribution to wild C.oleifera distribution.The population genetic structure of wild C.oleifera could be divided into two groups:in cold winter(BIO6≤0℃)and warm winter(BIO6>0℃)areas.Wild C.oleifera in cold winter areas might have experienced stronger selection pressures and population bottlenecks with lower N_(e) than those in warm winter areas.155 singlenucleotide polymorphisms(SNPs)were significantly correlated with the key bioclimatic variables(106 SNPs significantly correlated with BIO6).Twenty key SNPs and 15 key copy number variation regions(CNVRs)were found with genotype differentiation>50%between the two groups of wild C.oleifera.Key SNPs in cis-regulatory elements might affect the expression of key genes associated with freezing tolerance,and they were also found within a CNVR suggesting interactions between them.Some key CNVRs in the exon regions were closely related to the differentially expressed genes under freezing stress.The findings suggest that rich SNPs and CNVRs in polyploid trees may contribute to the adaptive evolution to freezing stress.展开更多
Nonlinear variations in the coordinate time series of global navigation satellite system(GNSS) reference stations are strongly correlated with surface displacements caused by environmental loading effects,including at...Nonlinear variations in the coordinate time series of global navigation satellite system(GNSS) reference stations are strongly correlated with surface displacements caused by environmental loading effects,including atmospheric, hydrological, and nontidal ocean loading. Continuous improvements in the accuracy of surface mass loading products, performance of Earth models, and precise data-processing technologies have significantly advanced research on the effects of environmental loading on nonlinear variations in GNSS coordinate time series. However, owing to theoretical limitations, the lack of high spatiotemporal resolution surface mass observations, and the coupling of GNSS technology-related systematic errors, environmental loading and nonlinear GNSS reference station displacements remain inconsistent. The applicability and capability of these loading products across different regions also require further evaluation. This paper outlines methods for modeling environmental loading, surface mass loading products, and service organizations. In addition, it summarizes recent advances in applying environmental loading to address nonlinear variations in global and regional GNSS coordinate time series. Moreover, the scientific questions of existing studies are summarized, and insights into future research directions are provided. The complex nonlinear motion of reference stations is a major factor limiting the accuracy of the current terrestrial reference frame. Further refining the environmental load modeling method, establishing a surface mass distribution model with high spatiotemporal resolution and reliability, exploring other environmental load factors such as ice sheet and artificial mass-change effects, and developing an optimal data-processing model and strategy for reprocessing global reference station data consistently could contribute to the development of a millimeter-level nonlinear motion model for GNSS reference stations with actual physical significance and provide theoretical support for establishing a terrestrial reference frame with 1 mm accuracy by 2050.展开更多
An extraordinary tropical cyclone-remote rainstorm with a 24-hour precipitation amount of 624.1 mm occurred in Zhengzhou,China,on 20 July 2021,during which a severe hourly precipitation amount of 201.9 mm at 1700 LST(...An extraordinary tropical cyclone-remote rainstorm with a 24-hour precipitation amount of 624.1 mm occurred in Zhengzhou,China,on 20 July 2021,during which a severe hourly precipitation amount of 201.9 mm at 1700 LST(LST=UTC+8)caused significant economic losses and casualties.Observational analysis and backward trajectory modeling showed that low-level water vapor for this extraordinary rainstorm was transported by the southeasterly jet below 900 hPa from the intensifying Typhoon In-Fa(2021)in the western North Pacific(low-level southeasterly channel).Although the southerly flow between 900 and 800 hPa brought water vapor from the developing Typhoon Cempaka in the South China Sea(low-level southerly channel),it did not converge over Zhengzhou.展开更多
The dynamics of network power response play a crucial role in system stability.However,the integration of power electronic equipment leads to amplitude and angular frequency(abbreviated as"frequency")time-va...The dynamics of network power response play a crucial role in system stability.However,the integration of power electronic equipment leads to amplitude and angular frequency(abbreviated as"frequency")time-varying characteristics of the node voltage during dynamic processes.As a result,traditional calcu-lation methods for and characteristics of the power response of the network based on phasor and impe-dance lose their validity.Therefore,this paper undertakes mathematical calculations to reveal the power response of a network under excitation by voltage with time-varying amplitude and frequency(TVAF),relying on the original mathematical relationships and superimposed step response.Then,the multi-timescale characteristics of both the active and reactive power of the network are explored physically.Additionally,this paper reveals a new phenomenon of storing and releasing the active and reactive power of the network.To meet practical engineering requirements,a simplified power expression is presented.Finally,the theoretical analysis is validated through time-domain simulations.展开更多
Maize(Zea mays)is highly susceptible to waterlogging stress,which reduces both the yield and quality of this important crop.However,the molecular mechanism governing waterlogging tolerance is poorly understood.In this...Maize(Zea mays)is highly susceptible to waterlogging stress,which reduces both the yield and quality of this important crop.However,the molecular mechanism governing waterlogging tolerance is poorly understood.In this study,we identify a waterlogging-and ethylene-inducible gene ZmEREB179 that encodes an ethylene response factor(ERF)localized in the nucleus.Overexpression of ZmEREB179 in maize increases the sensitivity to waterlogging stress.Conversely,the zmereb179 knockout mutants are more tolerant to waterlogging,suggesting that ZmEREB179 functions as a negative regulator of waterlogging tolerance.A transcriptome analysis of the ZmEREB179-overexpressing plants reveals that the ERF-type transcription factor modulates the expression of various stress-related genes,including ZmEREB180.We find that ZmEREB179 directly targets the ZmEREB180 promoter and represses its expression.Notably,the analysis of a panel of 220 maize inbred lines reveals that genetic variations in the ZmEREB179 promoter(Hap2)are highly associated with waterlogging resistance.The functional association of Hap2 with waterlogging resistance is tightly co-segregated in two F2 segregating populations,highlighting its potential applications in breeding programs.Our findings shed light on the involvement of the transcriptional cascade of ERF genes in regulating plant-waterlogging tolerance.展开更多
Nutrient uptake status dominates phytoplankton biomass and community structure in the Southern Ocean during austral summer,yet how nutrient utilization variability responds to phytoplankton community succession is sti...Nutrient uptake status dominates phytoplankton biomass and community structure in the Southern Ocean during austral summer,yet how nutrient utilization variability responds to phytoplankton community succession is still unclear,partly due to lack of data spanning the entire summer.In this study,nitrate,phosphate,and silicate combined with temperature,salinity,and apparent oxygen utilization(AOU)were analyzed along 45°E in the Cosmonaut Sea during December 2019,January 2021,and February 2022.The variations in nutrient utilization in the euphotic layer were studied using biogeochemical tracers,and seasonal nutrient depletion was also estimated.The results showed that nutrient distribution varied significantly from December to February.Significant positive correlations were observed for nitrate and silicate concentrations with salinity and AOU,indicating that nutrient distributions were mainly influenced by water mass and phytoplankton production.Increasing∆[N*]and decreasing∆[Si*]in the upper 50 m were observed south of 63.5°S from December to February,which possibly contributed to a progressive shift in dominant phytoplankton population from Phaeocystis antarctica to diatoms.The seasonal nutrient depletion generally increased from December to February.Moreover,the consumption of silicate substantially increased compared to nitrate,indicating that the abundance of diatoms was increasing with time during the austral summer.Our observations suggest that nutrient utilization status is closely related to phytoplankton community structure in the euphotic layer of the Cosmonaut Sea.展开更多
BACKGROUND The topography between the common carotid artery(CA),internal CA,and external CA(ECA)with the greater horn of the hyoid bone(GHHB)is of particular importance for anatomists,radiologists and neck surgeons.AI...BACKGROUND The topography between the common carotid artery(CA),internal CA,and external CA(ECA)with the greater horn of the hyoid bone(GHHB)is of particular importance for anatomists,radiologists and neck surgeons.AIM To investigate these topographical relationships emphasizing anatomical classification,sexual dimorphism,and clinical significance.METHODS A retrospective study was performed on 224 computed tomography angiographies from a cohort comprising 161 male and 63 female patients,with a mean age of 63.2 years.Multiplanar and three-dimensional reconstructions were executed utilizing Horos software.The spatial relationships between the CA and hyoid bone were categorized based on the 12-type classification system delineated by Manta et al in 2023.The data were subsequently stratified by sex and laterality.RESULTS Type 0(no arterial contact with the GHHB)was the most common configuration(46.9%),followed by type VI(ECA lateral to GHHB,23.9%)and type VIII(internal CA and ECA lateral to GHHB,13.2%).Bilateral symmetry was present in 54.02%of cases,mainly in males.Statistically significant sex-based differences were found(P=0.012),while laterality was not significant(P=0.779).CONCLUSION Carotid–hyoid topography displays significant anatomical variation with clinically essential patterns.Non-null variants,such as types VI and VIII,may increase the risk of dynamic carotid compression,especially in younger patients with cryptogenic cerebrovascular symptoms.Recognizing these variants during preoperative imaging is crucial to minimize surgical risk and inform patient care.展开更多
This study examines in-situ temperature profiles in three representative sections,namely,the Dalian-Chengshantou(DC),the Chengshantou-Changsangot(CC),and the 36°N,to delineate the interannual variations of the Ye...This study examines in-situ temperature profiles in three representative sections,namely,the Dalian-Chengshantou(DC),the Chengshantou-Changsangot(CC),and the 36°N,to delineate the interannual variations of the Yellow Sea Cold Water Mass(YSCWM)and investigate their potential connections,along with forcing factors,across different regions.The findings reveal the fol-lowing insights:1)The YSCWM experiences warming trends at DC,CC,and the western segment of the 36°N,revealing correspond-ing minimum temperature rates of 0.021℃/yr,0.043℃/yr,and 0.063℃/yr,respectively.Conversely,the eastern portion of the 36°N displays a slight cooling trend,resulting in a pronounced zonal disparity in long-term temperature trends.2)The changes in the YSCWM are closely linked to the atmospheric wind patterns.Notably,the weakening of northerly winds during winter corresponds to the rise in YSCWM temperature,which is accompanied by a westward shift in the cold core of the 36°N section.3)Correlation analysis with factors such as the Arctic Oscillation(AO),Pacific Decadal Oscillation(PDO),and El Niño-Southern Oscillation(EN-SO),etc.,indicates that changes in large-scale climate systems influence the spatiotemporal variations of the YSCWM,resulting in seasonal differences.展开更多
Since the 1975 M_(S)7.3 Haicheng earthquake,spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors.Recent technical advances in terrestrial gravity observation...Since the 1975 M_(S)7.3 Haicheng earthquake,spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors.Recent technical advances in terrestrial gravity observation,along with the construction of a high-precision mobile gravity network covering Chinese mainland,have positioned temporal gravity variations(GVs)as an important tool for clarifying the signal characteristics and dynamic mechanisms of crustal sources.Reportedly,crustal mass transfer,which is affected by stress state and structural environment,alters the characteristics of the regional gravity field,thus serving as an indicator for locations of moderate to strong earthquakes and a seismology-independent predictor for regions at risk for strong earthquakes.Therefore,quantitatively tracking time-varying gravity is of paramount importance to enhance the effectiveness of earthquake prediction.In this study,we divided the areas effectively covered by the terrestrial mobile gravity network in the Sichuan-Yunnan region into small grids based on the latest observational data(since 2018)from the network.Next,we calculated the 1-and 3-year GVs and gravity gradient indicators(amplitude of analytic signal,AAS;total horizontal derivative,THD;and amplitude of vertical gradient,AVG)to quantitatively characterize variations in regional time-varying gravity field.Next,we assessed the effectiveness of gravity field variations in predicting earthquakes in the Sichuan-Yunnan region using Molchan diagrams constructed for gravity signals of 13 earthquakes(M≥5.0;occurred between 2021 and 2024)within the terrestrial mobile gravity network.The results reveal a certain correspondence between gravity field variations and the locations of moderate and strong earthquakes in the Sichuan-Yunnan region.Furthermore,the 3-year AAS and AVG outperform the 3-year THD in predicting subsequent seismic events.Notably,the AAS and AVG showed large probability gains prior to the M_(S)6.8 Luding earthquake,indicating their potential for earthquake prediction.展开更多
This study evaluated corn kernel drying performance and quality changes using hot air drying(HAD)and infrared drying(ID)across temperatures ranging from 55℃ to 80℃.Optimal drying parameters were determined by using ...This study evaluated corn kernel drying performance and quality changes using hot air drying(HAD)and infrared drying(ID)across temperatures ranging from 55℃ to 80℃.Optimal drying parameters were determined by using the entropy weight method,with drying time,specific energy consumption,damage rate,fatty acids,starch,polyphenols,and flavonoids as indicators.Results demonstrated that ID significantly outperformed HAD,achieving drying times up to 20%shorter and reducing specific energy consumption and kernel damage by up to 79.3%and 66.7%,respectively,while also better preserving quality attributes.Both methods exhibited drying profiles characterized by acceleration,constant,and falling rate periods,although the constant rate phase was distinctly observable only at lower temperatures.The effective moisture diffusivity under ID was consistently higher than that under HAD,with a maximum increase of 20.4%.The optimal drying conditions were HAD at 65℃ and ID at 80℃.A BP model was also developed and it showed better predictive performance and adaptability than classical mathematical models.展开更多
Marine heatwaves(MHWs)in the East China Sea(ECS),especially those occurring on the ocean bottom(referred to as bottom marine heatwaves,BMHWs),can significantly affect regional ecosystems.However,our understanding of t...Marine heatwaves(MHWs)in the East China Sea(ECS),especially those occurring on the ocean bottom(referred to as bottom marine heatwaves,BMHWs),can significantly affect regional ecosystems.However,our understanding of the seasonal variations in the MHWs in the ECS remains limited.This study investigates the characteristics of MHWs in the ECS in summer and winter using high-resolution oceanic reanalysis.Our analyses reveal distinct spatial patterns of BMHWs in these seasons.During summer,the Taiwan Warm Current plays a crucial role in transporting warm water northward,potentially leading to intense BMHWs on the central ECS shelf.These BMHW events usually occur independently of surface warming due to strong stratification in summer.Conversely,winter BMHWs are more prevalent in coastal regions under the influence of coastal currents and typically feature consistent warming from surface to bottom with a deepened mixed layer.These findings inform the coherent vertical structure and driving mechanisms of MHWs in the ECS,which are essential for predicting and managing these extreme events in the future.展开更多
As the Arctic undergoes rapid warming and sea ice continues to decline,Ocean-to-Ice Heat Flux(OIHF)plays a crucial role in regulating sea ice dynamics.This study investigates the seasonal variations in ocean-to-ice he...As the Arctic undergoes rapid warming and sea ice continues to decline,Ocean-to-Ice Heat Flux(OIHF)plays a crucial role in regulating sea ice dynamics.This study investigates the seasonal variations in ocean-to-ice heat flux in north of the Fram Strait using the regional Arctic Ocean/sea ice reanalysis product from 1991 to 2020.The analysis reveals that the OIHF exhibits significant seasonal variability,with a pronounced peak during winter in north of the Fram Strait,driven by inflows of Atlantic water.Warm Atlantic water intrusion begins in October,reaches its peak in January and February,and results in a delayed increase in OIHF,with maximum flux observed 2−3 months later.These results highlight the significant role of Atlantic water inflows in influencing Arctic sea ice dynamics and emphasize the need for further investigation into the coupled ocean-atmosphere processes that govern seasonal fluctuations in OIHF.展开更多
Based on the data of meteorological elements and concentration of negative ions in the county town station,Luguhe station and Yunjishan station during 2020-2024,the temporal and spatial variations in the concentration...Based on the data of meteorological elements and concentration of negative ions in the county town station,Luguhe station and Yunjishan station during 2020-2024,the temporal and spatial variations in the concentration of negative ions and their influencing factors in Xinfeng County were analyzed.The results show that the concentration of negative ions was the highest in summer,followed by spring;it was lower in autumn and the lowest in winter.In terms of diurnal variations,it was higher in the early morning and night,and lower in the noon and afternoon,which was closely related to the diurnal variations of human activities and meteorological conditions.The factors that affect the concentration of negative ions in the air are more complex.Besides meteorological factors,vegetation,altitude,human activities and other factors should be considered.展开更多
The Aleutian Low(AL)is a dominant feature of the mean circulation in the North Pacific during the winter season.The background stationary wave,air-sea interaction,and transient eddies over the North Pacific exert dist...The Aleutian Low(AL)is a dominant feature of the mean circulation in the North Pacific during the winter season.The background stationary wave,air-sea interaction,and transient eddies over the North Pacific exert distinct impacts on the interannual variations of the AL intensity and position.In this study,we adopt the quasi-geostrophic geopotential tendency equation to investigate the roles of various physical processes in the maintenance and interannual variations of this system.The results show that absolute vorticity advection plays the most important role in the formation and maintenance of AL intensity,while high-frequency transient eddies contribute most to the meridional and zonal shifts of the AL.The high-frequency transient eddy vorticity forcing affects the AL through the barotropic energy conversion process,and,in turn,the AL enhances the high-frequency transient eddies through the baroclinic energy conversion process,forming a positive feedback.The associated high-frequency eddy kinetic energy anomalies exhibit an eastward movement toward the east coast of North America in the years of an intensified AL,which explains why a strengthened AL is often accompanied by an eastward movement.Furthermore,the energy conversion terms of high-frequency transient eddies are mostly located over the extratropical eastern North Pacific,leading to asymmetric features in the zonal movement of the AL.展开更多
基金National Basic Research Program of China(973 Program,2012CB957804)Natural Science Foundation of China(41175051)
文摘Based on the ERA reanalysis winds data, the multi-time scale variations of Somali jet are analyzed synthetically. The jet's influences on rainfall in China on interannual, interdecadal and sub-monthly scales are also studied using correlation and composite analyses. The results demonstrate that the interdecadal variations of the jet are significant.The Somali jet became weaker in the 1960 s and became the weakest in the early 1970 s before enhancing slowly in the late 1970 s. Moreover, the relation between the Somali jet and summer precipitation in China is close, but varies on different timescales. Preliminary analysis shows that the intensity variations in May and June during the early days of establishment are well correlated with summer precipitation in China. The Somali jet intensity on the interdecadal scale is closely related with interdecadal variations of the precipitation in China. Regardless of leading or contemporaneous correlation, the correlations between the Somali jet intensity and the rainfall in northern and southern China show obvious interdecadal variations. Moreover, the link between the anomalies of the jet intensity in May-August and precipitation evolution on synoptic scale in China is further studied. China has more rainfall with positive anomalies of the Somali jet but less rainfall with negative anomalies during the active period of the jet. The influence of positive Somali jet anomalies on China precipitation is more evident.
基金supported by the National Natural Science Foundation of China(Grant Nos.42027804,41775026,and 41075012)。
文摘Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and reanalysis data(MERRA-2)from March 2007 to February 2015(eight years).The horizontal distribution reveals lower cirrus fraction values in the northern SCS and higher values in the southern region,with minima observed in March and April and maxima sequentially occurring in August(northern SCS,NSCS),September(middle SCS,MSCS),and December(southern SCS,SSCS).Vertically,the cirrus fraction peaks in summer and reaches its lowest levels in spring.Opaque cirrus dominates during summer in the NSCS and MSCS,comprising 53.6%and 55.9%,respectively,while the SSCS exhibits a higher frequency of opaque cirrus relative to other cloud types.Subvisible cirrus clouds have the lowest frequency year-round,whereas thin cirrus is most prominent in winter in the NSCS(46.3%)and in spring in the MSCS(45.3%).A case study from September 2021 further explores the influence of ice crystal habits on brightness temperature(BT)over the SCS.Simulations utilizing five ice crystal shapes from the ARTS DDA(Atmospheric Radiative Transfer Simulator Discrete Dipole Approximation)database and the RTTOV 12.4 radiative transfer model reveal that the 8-column-aggregate shape best represents BT in the NSCS and SSCS,while the large-block-aggregate shape performs better in the SSCS.
基金supported by the CAS Pioneer Hundred Talents Program and Second Tibetan Plateau Scientific Expedition Research Program(2019QZKK0708)as well as the Basic Research Program of Qinghai Province:Lithospheric Geomagnetic Field of the Qinghai‒Tibet Plateau and the Relationship with Strong Earthquakes(2021-ZJ-969Q).
文摘The National Geophysical Data Center(NGDC)of the United States has collected aeromagnetic data for input into a series of geomagnetic models to improve model resolution;however,in the Tibetan Plateau region,ground-based observations remain insufficient to clearly reflect the characteristics of the region’s lithospheric magnetism.In this study,we evaluate the lithospheric magnetism of the Tibetan Plateau by using a 3D surface spline model based on observations from>200 newly constructed repeat stations(portable stations)to determine the spatial distribution of plateau geomagnetism,as well as its correlation with the tectonic features of the region.We analyze the relationships between M≥5 earthquakes and lithospheric magnetic field variations on the Tibetan Plateau and identify regions susceptible to strong earthquakes.We compare the geomagnetic results with those from an enhanced magnetic model(EMM2015)developed by the NGDC and provide insights into improving lithospheric magnetic field calculations in the Tibetan Plateau region.Further research reveals that these magnetic anomalies exhibit distinct differences from the magnetic-seismic correlation mechanisms observed in other tectonic settings;here,they are governed primarily by the combined effects of compressional magnetism,thermal magnetism,and deep thermal stress.This study provides new evidence of geomagnetic anomalies on the Tibetan Plateau,interprets them physically,and demonstrates their potential for identifying seismic hazard zones on the Plateau.
文摘Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive degeneration of upper and lower motor neurons in the brainstem and spinal cord,leading to muscle weakness,paralysis,and respiratory failure (Morgan and Orrell,2016).
基金supported by the National Natural Science Foundation of China(Nos.42030707,72394404)the International Partnership Program of the Chinese Academy of Sciences(No.121311KYSB20190029)the Fundamental Research Fund for the Central Universities(Nos.20720210083,20720210082).
文摘Halocarbons play a vital role in ozone depletion and global warming,and are regulated by the Montreal Protocol(MP)and its amendments.China has been identified as an important contributor to the halocarbon emissions,but the regional sources of halocarbons in China are not yet well comprehended.To investigate the characteristics,emissions,and source profiles,this study conducted a field campaign in Xiamen,a coastal city in southeastern China.Higher enhancements were found in the unregulated halocarbons(CH_(3)Cl,CH_(2)Cl_(2),CHCl_(3))than in the MP eliminated species(CCl_(4),CH_(3)Br)and theMP controlled species(HCFCs,HFCs).Many of the measured halocarbons varied seasonally and regionally,depending on the anthropogenic sources and atmospheric transport.Backward trajectory analysis showed that the air masses from inland were polluted over Shandong,Hebei,and northern Fujian in the cold season,while the air masses fromthe sea in the warm season were clean.Different air masses in two seasons were associated with the halocarbon patterns in the study area.Industrial activities,especially solvent usage,were the primary sources of halocarbons.The emission hot spots in Fujian Province were concentrated in Sanming,Fuzhou,and Xiamen,and the unregulated halocarbons made the largest contribution.This study provides an insight for a deep understanding of the characteristics and potential sources of halocarbons,and for strengthened management of halocarbons in China.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(42475003)Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2023SP209)。
文摘Southerly moisture surges over the central South China Sea(SCS)are characterized by the strengthening of lowlevel southerlies that transport moisture northward from the Pacific or Indian Oceans to South China.These surge events typically occur for days in the early-summer season(from April to June)and can lead to heavy rains in South China.This study categorizes surge events into three types of flow patterns and examines their multiscale variations and impacts on rainfall.The first type occurs mainly in April,with the southeasterlies enhanced by a deepening trough in South China and the western Pacific subtropical high established over the SCS.The second type of surge events mostly appears in June,featuring the prevailing southwesterlies of summer monsoon from the Indian Ocean during the active phases of intraseasonal oscillations.Most surge events exhibit semi-diurnal variations with morning and afternoon peaks of northward moisture fluxes.Specifically,the first type features a dominant afternoon peak,while the second type shows a dominant early-morning peak,which is induced by thermal contrast between the Indochina Peninsula and the SCS.In general,the surge events enhance moisture convergence and increase rainfall downstream in South China,but they show some regional differences.The second type strengthens moisture convergence and rainfall in coastal regions with a morning peak.In contrast,the first type enhances inland rainfall with a morning peak,while moisture divergence dominates coastal regions.The third type of surge events denotes transitional conditions between the first two types,in terms of atmospheric circulations,diurnal cycles,and rainfall patterns.These results highlight a diversity of regional moisture surges and related rainfall ranging from diurnal to sub-seasonal scales.
基金funded by the National Natural Science Foundation of China(grant no.32270238 and 31870311).
文摘Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress,while hexaploid wild Camellia oleifera shows strong freezing tolerance.As a valuable genetic resource of woody oil crop C.oleifera,wild C.oleifera can serve as a case for studying the molecular bases of adaptive evolution to freezing stress.Here,47 wild C.oleifera from 11 natural distribution sites in China and 4 relative species of C.oleifera were selected for genome sequencing.“Min Temperature of Coldest Month”(BIO6)had the highest comprehensive contribution to wild C.oleifera distribution.The population genetic structure of wild C.oleifera could be divided into two groups:in cold winter(BIO6≤0℃)and warm winter(BIO6>0℃)areas.Wild C.oleifera in cold winter areas might have experienced stronger selection pressures and population bottlenecks with lower N_(e) than those in warm winter areas.155 singlenucleotide polymorphisms(SNPs)were significantly correlated with the key bioclimatic variables(106 SNPs significantly correlated with BIO6).Twenty key SNPs and 15 key copy number variation regions(CNVRs)were found with genotype differentiation>50%between the two groups of wild C.oleifera.Key SNPs in cis-regulatory elements might affect the expression of key genes associated with freezing tolerance,and they were also found within a CNVR suggesting interactions between them.Some key CNVRs in the exon regions were closely related to the differentially expressed genes under freezing stress.The findings suggest that rich SNPs and CNVRs in polyploid trees may contribute to the adaptive evolution to freezing stress.
基金supported by the Basic Science Center Project of the National Natural Science Foundation of China(42388102)the National Natural Science Foundation of China(42174030)+2 种基金the Special Fund of Hubei Luojia Laboratory(220100020)the Major Science and Technology Program for Hubei Province(2022AAA002)the Fundamental Research Funds for the Central Universities of China(2042022dx0001 and 2042023kfyq01)。
文摘Nonlinear variations in the coordinate time series of global navigation satellite system(GNSS) reference stations are strongly correlated with surface displacements caused by environmental loading effects,including atmospheric, hydrological, and nontidal ocean loading. Continuous improvements in the accuracy of surface mass loading products, performance of Earth models, and precise data-processing technologies have significantly advanced research on the effects of environmental loading on nonlinear variations in GNSS coordinate time series. However, owing to theoretical limitations, the lack of high spatiotemporal resolution surface mass observations, and the coupling of GNSS technology-related systematic errors, environmental loading and nonlinear GNSS reference station displacements remain inconsistent. The applicability and capability of these loading products across different regions also require further evaluation. This paper outlines methods for modeling environmental loading, surface mass loading products, and service organizations. In addition, it summarizes recent advances in applying environmental loading to address nonlinear variations in global and regional GNSS coordinate time series. Moreover, the scientific questions of existing studies are summarized, and insights into future research directions are provided. The complex nonlinear motion of reference stations is a major factor limiting the accuracy of the current terrestrial reference frame. Further refining the environmental load modeling method, establishing a surface mass distribution model with high spatiotemporal resolution and reliability, exploring other environmental load factors such as ice sheet and artificial mass-change effects, and developing an optimal data-processing model and strategy for reprocessing global reference station data consistently could contribute to the development of a millimeter-level nonlinear motion model for GNSS reference stations with actual physical significance and provide theoretical support for establishing a terrestrial reference frame with 1 mm accuracy by 2050.
基金supported by the National Natural Science Foundation of China(Grant No.42305007).
文摘An extraordinary tropical cyclone-remote rainstorm with a 24-hour precipitation amount of 624.1 mm occurred in Zhengzhou,China,on 20 July 2021,during which a severe hourly precipitation amount of 201.9 mm at 1700 LST(LST=UTC+8)caused significant economic losses and casualties.Observational analysis and backward trajectory modeling showed that low-level water vapor for this extraordinary rainstorm was transported by the southeasterly jet below 900 hPa from the intensifying Typhoon In-Fa(2021)in the western North Pacific(low-level southeasterly channel).Although the southerly flow between 900 and 800 hPa brought water vapor from the developing Typhoon Cempaka in the South China Sea(low-level southerly channel),it did not converge over Zhengzhou.
基金supported in part by the National Natural Science Fundation of China(52225704 and 52107096).
文摘The dynamics of network power response play a crucial role in system stability.However,the integration of power electronic equipment leads to amplitude and angular frequency(abbreviated as"frequency")time-varying characteristics of the node voltage during dynamic processes.As a result,traditional calcu-lation methods for and characteristics of the power response of the network based on phasor and impe-dance lose their validity.Therefore,this paper undertakes mathematical calculations to reveal the power response of a network under excitation by voltage with time-varying amplitude and frequency(TVAF),relying on the original mathematical relationships and superimposed step response.Then,the multi-timescale characteristics of both the active and reactive power of the network are explored physically.Additionally,this paper reveals a new phenomenon of storing and releasing the active and reactive power of the network.To meet practical engineering requirements,a simplified power expression is presented.Finally,the theoretical analysis is validated through time-domain simulations.
基金supported by the science and technology major program of Hubei Province(2022ABA001)the National Key Research and Development Program of Shandong Province(2022CXPT014)the Knowledge Innovation Program of Wuhan-Shugung Project(2023020201020413).
文摘Maize(Zea mays)is highly susceptible to waterlogging stress,which reduces both the yield and quality of this important crop.However,the molecular mechanism governing waterlogging tolerance is poorly understood.In this study,we identify a waterlogging-and ethylene-inducible gene ZmEREB179 that encodes an ethylene response factor(ERF)localized in the nucleus.Overexpression of ZmEREB179 in maize increases the sensitivity to waterlogging stress.Conversely,the zmereb179 knockout mutants are more tolerant to waterlogging,suggesting that ZmEREB179 functions as a negative regulator of waterlogging tolerance.A transcriptome analysis of the ZmEREB179-overexpressing plants reveals that the ERF-type transcription factor modulates the expression of various stress-related genes,including ZmEREB180.We find that ZmEREB179 directly targets the ZmEREB180 promoter and represses its expression.Notably,the analysis of a panel of 220 maize inbred lines reveals that genetic variations in the ZmEREB179 promoter(Hap2)are highly associated with waterlogging resistance.The functional association of Hap2 with waterlogging resistance is tightly co-segregated in two F2 segregating populations,highlighting its potential applications in breeding programs.Our findings shed light on the involvement of the transcriptional cascade of ERF genes in regulating plant-waterlogging tolerance.
基金The National Polar Special Program“Impact and Response of Antarctic Seas to Climate Change”under contract Nos IRASCC 01-01-02 and IRASCC 02-02the National Key Research and Development Program of China under contract No.2022YFE0136500+1 种基金the National Natural Science Foundation of China(NSFC)under contract Nos 41976228,42276255 and 42176227the Scientific Research Fund of the Second Institute of Oceanography under contract Nos JG2011,JG2211 and JG2013.
文摘Nutrient uptake status dominates phytoplankton biomass and community structure in the Southern Ocean during austral summer,yet how nutrient utilization variability responds to phytoplankton community succession is still unclear,partly due to lack of data spanning the entire summer.In this study,nitrate,phosphate,and silicate combined with temperature,salinity,and apparent oxygen utilization(AOU)were analyzed along 45°E in the Cosmonaut Sea during December 2019,January 2021,and February 2022.The variations in nutrient utilization in the euphotic layer were studied using biogeochemical tracers,and seasonal nutrient depletion was also estimated.The results showed that nutrient distribution varied significantly from December to February.Significant positive correlations were observed for nitrate and silicate concentrations with salinity and AOU,indicating that nutrient distributions were mainly influenced by water mass and phytoplankton production.Increasing∆[N*]and decreasing∆[Si*]in the upper 50 m were observed south of 63.5°S from December to February,which possibly contributed to a progressive shift in dominant phytoplankton population from Phaeocystis antarctica to diatoms.The seasonal nutrient depletion generally increased from December to February.Moreover,the consumption of silicate substantially increased compared to nitrate,indicating that the abundance of diatoms was increasing with time during the austral summer.Our observations suggest that nutrient utilization status is closely related to phytoplankton community structure in the euphotic layer of the Cosmonaut Sea.
文摘BACKGROUND The topography between the common carotid artery(CA),internal CA,and external CA(ECA)with the greater horn of the hyoid bone(GHHB)is of particular importance for anatomists,radiologists and neck surgeons.AIM To investigate these topographical relationships emphasizing anatomical classification,sexual dimorphism,and clinical significance.METHODS A retrospective study was performed on 224 computed tomography angiographies from a cohort comprising 161 male and 63 female patients,with a mean age of 63.2 years.Multiplanar and three-dimensional reconstructions were executed utilizing Horos software.The spatial relationships between the CA and hyoid bone were categorized based on the 12-type classification system delineated by Manta et al in 2023.The data were subsequently stratified by sex and laterality.RESULTS Type 0(no arterial contact with the GHHB)was the most common configuration(46.9%),followed by type VI(ECA lateral to GHHB,23.9%)and type VIII(internal CA and ECA lateral to GHHB,13.2%).Bilateral symmetry was present in 54.02%of cases,mainly in males.Statistically significant sex-based differences were found(P=0.012),while laterality was not significant(P=0.779).CONCLUSION Carotid–hyoid topography displays significant anatomical variation with clinically essential patterns.Non-null variants,such as types VI and VIII,may increase the risk of dynamic carotid compression,especially in younger patients with cryptogenic cerebrovascular symptoms.Recognizing these variants during preoperative imaging is crucial to minimize surgical risk and inform patient care.
文摘This study examines in-situ temperature profiles in three representative sections,namely,the Dalian-Chengshantou(DC),the Chengshantou-Changsangot(CC),and the 36°N,to delineate the interannual variations of the Yellow Sea Cold Water Mass(YSCWM)and investigate their potential connections,along with forcing factors,across different regions.The findings reveal the fol-lowing insights:1)The YSCWM experiences warming trends at DC,CC,and the western segment of the 36°N,revealing correspond-ing minimum temperature rates of 0.021℃/yr,0.043℃/yr,and 0.063℃/yr,respectively.Conversely,the eastern portion of the 36°N displays a slight cooling trend,resulting in a pronounced zonal disparity in long-term temperature trends.2)The changes in the YSCWM are closely linked to the atmospheric wind patterns.Notably,the weakening of northerly winds during winter corresponds to the rise in YSCWM temperature,which is accompanied by a westward shift in the cold core of the 36°N section.3)Correlation analysis with factors such as the Arctic Oscillation(AO),Pacific Decadal Oscillation(PDO),and El Niño-Southern Oscillation(EN-SO),etc.,indicates that changes in large-scale climate systems influence the spatiotemporal variations of the YSCWM,resulting in seasonal differences.
基金funded by the National Key R&D Program of China(Nos.2023YFE0101800 and 2023YFC 3007305)National Natural Science Foundation of China(Nos.42004069 and 42204093)Special Fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB24X24).
文摘Since the 1975 M_(S)7.3 Haicheng earthquake,spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors.Recent technical advances in terrestrial gravity observation,along with the construction of a high-precision mobile gravity network covering Chinese mainland,have positioned temporal gravity variations(GVs)as an important tool for clarifying the signal characteristics and dynamic mechanisms of crustal sources.Reportedly,crustal mass transfer,which is affected by stress state and structural environment,alters the characteristics of the regional gravity field,thus serving as an indicator for locations of moderate to strong earthquakes and a seismology-independent predictor for regions at risk for strong earthquakes.Therefore,quantitatively tracking time-varying gravity is of paramount importance to enhance the effectiveness of earthquake prediction.In this study,we divided the areas effectively covered by the terrestrial mobile gravity network in the Sichuan-Yunnan region into small grids based on the latest observational data(since 2018)from the network.Next,we calculated the 1-and 3-year GVs and gravity gradient indicators(amplitude of analytic signal,AAS;total horizontal derivative,THD;and amplitude of vertical gradient,AVG)to quantitatively characterize variations in regional time-varying gravity field.Next,we assessed the effectiveness of gravity field variations in predicting earthquakes in the Sichuan-Yunnan region using Molchan diagrams constructed for gravity signals of 13 earthquakes(M≥5.0;occurred between 2021 and 2024)within the terrestrial mobile gravity network.The results reveal a certain correspondence between gravity field variations and the locations of moderate and strong earthquakes in the Sichuan-Yunnan region.Furthermore,the 3-year AAS and AVG outperform the 3-year THD in predicting subsequent seismic events.Notably,the AAS and AVG showed large probability gains prior to the M_(S)6.8 Luding earthquake,indicating their potential for earthquake prediction.
基金financially supported by the Natural Science Foundation of Hunan Province(project No.2024JJ8037:https://kjt.hunan.gov.cn/kjt/xxgk/tzgg/tzgg_1/202403/t20240311_33144606.html,accessed on 27 October 2025)。
文摘This study evaluated corn kernel drying performance and quality changes using hot air drying(HAD)and infrared drying(ID)across temperatures ranging from 55℃ to 80℃.Optimal drying parameters were determined by using the entropy weight method,with drying time,specific energy consumption,damage rate,fatty acids,starch,polyphenols,and flavonoids as indicators.Results demonstrated that ID significantly outperformed HAD,achieving drying times up to 20%shorter and reducing specific energy consumption and kernel damage by up to 79.3%and 66.7%,respectively,while also better preserving quality attributes.Both methods exhibited drying profiles characterized by acceleration,constant,and falling rate periods,although the constant rate phase was distinctly observable only at lower temperatures.The effective moisture diffusivity under ID was consistently higher than that under HAD,with a maximum increase of 20.4%.The optimal drying conditions were HAD at 65℃ and ID at 80℃.A BP model was also developed and it showed better predictive performance and adaptability than classical mathematical models.
基金The National Natural Science Foundation of China under contract No.42030410the Laoshan Laboratory under contract Nos LSKJ202202404 and LSKJ202202403+2 种基金the Startup Foundation for Introducing Talent of Nanjing University of Information Science and TechnologyJiangsu Innovation Research Group under contract No.JSSCTD202346Jiangsu Funding Program for Excellent Postdoctoral Talent under contract No.2023ZB690。
文摘Marine heatwaves(MHWs)in the East China Sea(ECS),especially those occurring on the ocean bottom(referred to as bottom marine heatwaves,BMHWs),can significantly affect regional ecosystems.However,our understanding of the seasonal variations in the MHWs in the ECS remains limited.This study investigates the characteristics of MHWs in the ECS in summer and winter using high-resolution oceanic reanalysis.Our analyses reveal distinct spatial patterns of BMHWs in these seasons.During summer,the Taiwan Warm Current plays a crucial role in transporting warm water northward,potentially leading to intense BMHWs on the central ECS shelf.These BMHW events usually occur independently of surface warming due to strong stratification in summer.Conversely,winter BMHWs are more prevalent in coastal regions under the influence of coastal currents and typically feature consistent warming from surface to bottom with a deepened mixed layer.These findings inform the coherent vertical structure and driving mechanisms of MHWs in the ECS,which are essential for predicting and managing these extreme events in the future.
基金The National Natural Science Foundation of China under contract Nos 42406259,42175172,and 41975134the Science Foundation for Youths of Hunan Province(Category C)under contract No.2025JJ60240.
文摘As the Arctic undergoes rapid warming and sea ice continues to decline,Ocean-to-Ice Heat Flux(OIHF)plays a crucial role in regulating sea ice dynamics.This study investigates the seasonal variations in ocean-to-ice heat flux in north of the Fram Strait using the regional Arctic Ocean/sea ice reanalysis product from 1991 to 2020.The analysis reveals that the OIHF exhibits significant seasonal variability,with a pronounced peak during winter in north of the Fram Strait,driven by inflows of Atlantic water.Warm Atlantic water intrusion begins in October,reaches its peak in January and February,and results in a delayed increase in OIHF,with maximum flux observed 2−3 months later.These results highlight the significant role of Atlantic water inflows in influencing Arctic sea ice dynamics and emphasize the need for further investigation into the coupled ocean-atmosphere processes that govern seasonal fluctuations in OIHF.
文摘Based on the data of meteorological elements and concentration of negative ions in the county town station,Luguhe station and Yunjishan station during 2020-2024,the temporal and spatial variations in the concentration of negative ions and their influencing factors in Xinfeng County were analyzed.The results show that the concentration of negative ions was the highest in summer,followed by spring;it was lower in autumn and the lowest in winter.In terms of diurnal variations,it was higher in the early morning and night,and lower in the noon and afternoon,which was closely related to the diurnal variations of human activities and meteorological conditions.The factors that affect the concentration of negative ions in the air are more complex.Besides meteorological factors,vegetation,altitude,human activities and other factors should be considered.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.42088101 and 42175023)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.316323005)the Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies(Grant No.2020B1212060025)。
文摘The Aleutian Low(AL)is a dominant feature of the mean circulation in the North Pacific during the winter season.The background stationary wave,air-sea interaction,and transient eddies over the North Pacific exert distinct impacts on the interannual variations of the AL intensity and position.In this study,we adopt the quasi-geostrophic geopotential tendency equation to investigate the roles of various physical processes in the maintenance and interannual variations of this system.The results show that absolute vorticity advection plays the most important role in the formation and maintenance of AL intensity,while high-frequency transient eddies contribute most to the meridional and zonal shifts of the AL.The high-frequency transient eddy vorticity forcing affects the AL through the barotropic energy conversion process,and,in turn,the AL enhances the high-frequency transient eddies through the baroclinic energy conversion process,forming a positive feedback.The associated high-frequency eddy kinetic energy anomalies exhibit an eastward movement toward the east coast of North America in the years of an intensified AL,which explains why a strengthened AL is often accompanied by an eastward movement.Furthermore,the energy conversion terms of high-frequency transient eddies are mostly located over the extratropical eastern North Pacific,leading to asymmetric features in the zonal movement of the AL.
