The Equatorial Atlantic Ocean,a region crucial to understanding Earth’s tectonic processes and advancing the theory of plate tectonics,remains the focus of extensive research aimed at unraveling its evolution.However...The Equatorial Atlantic Ocean,a region crucial to understanding Earth’s tectonic processes and advancing the theory of plate tectonics,remains the focus of extensive research aimed at unraveling its evolution.However,its complex structural setting and contentious formation timeline have posed significant challenges.Through a comprehensive review of contemporary scientific litera-ture,we have identified three distinct phases for its evolution:pre-breakup,syn-breakup,and post-breakup,providing more detailed in-sights into the tectonic evolution of the Equatorial Atlantic.Prior to 110 Myr,the African and South American Plates underwent stretching predominantly from North to South,with the emergence of the Parana plume.This condition has led to the formation of nu-merous fracture zones and a triple junction.During the syn-breakup phase,spanning from 110 Myr to 90 Myr,the central region of the Equatorial Atlantic fully opened up,establishing a connection between the northern and southern waterways.However,the develop-ment of multiple ridge segments separated by numerous fracture zones in the central Equatorial Atlantic exhibited considerable com-plexity.The underlying causes for these complex structural formations remain elusive.Following the Chicxulub meteorite impact around 66 Myr and the emergence of the Sierra Leone hotspot,a pair of oceanic plateau‘twins’and a series of seamount chains were formed as a result of mantle plume tails.Consequently,the timeline of the Equatorial Atlantic’s tectonic evolution has gradually be-come clearer.However,due to the extensive timescale and the multitude of events involved in its formation,disputes about the precise-timing of various events still remain.The evolution of the Equatorial Atlantic has witnessed numerous ridge propagations,hotspot formations,and meteorite impacts,highlighting the need for further investigation into their interactions.The absence of identified magnetic isochrons in the Equatorial region emphasizes the urgency of additional exploration and analysis of its geological and geo-physical data.展开更多
This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signa...This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.展开更多
Thermospheric neutral winds(TNWs)refer to the neutral gases in the thermosphere circulating as tides,which play a crucial role in the dynamics of the thermosphere-ionosphere system(TIS).Global geospace neutral winds,p...Thermospheric neutral winds(TNWs)refer to the neutral gases in the thermosphere circulating as tides,which play a crucial role in the dynamics of the thermosphere-ionosphere system(TIS).Global geospace neutral winds,particularly over the magnetic equator,have been a subject of study for several decades.However,despite the known importance of neutral winds,a comprehensive understanding and characterization of the winds is still lacking.Various ground-based and satellite missions have provided valuable information on the contribution of neutral winds to the global atmospheric dynamics.However,efforts in the global monitoring of neutral winds are still lacking,and the drivers behind the behavior of TNWs as well as their influence on the TIS remain incomplete.To address these knowledge gaps in the global circulation of TNWs,it is crucial to develop a deep understanding of the neutral wind characteristics over different regions.The low-latitude equatorial region in particular has been observed to exert complex influences on TNWs because of the unique effects of the Earth’s magnetic field at the dip equator.Studying neutral winds over this region will provide valuable insights into the unique dynamics and processes that occur in this region,thereby enhancing our understanding of their role in the overall dynamics of the TIS.Additionally,through empirical observations,an improved ability to accurately model and predict the behavior of this region can be achieved.This review article addresses challenges in understanding equatorial winds by reviewing historical measurements,current missions,and the interactions of ionospheric and thermospheric phenomena,emphasizing the need for comprehensive measurements to improve global atmospheric dynamics and weather forecasting.展开更多
Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while al...Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while also deepening our knowledge of stellar physics and solar system dynamics.Determining the solar cycles between 1600 and 1700-especially the post-1645 Maunder Minimum,characterized by significantly reduced solar activity-poses challenges to existing solar activity proxies.This study utilizes a new red equatorial auroral catalog from ancient Korean texts to establish solar cycle patterns from 1623 to 1700.Remarkably,a further reevaluation of the solar cycles between 1610 and 1755 identified a total of 13 cycles,diverging from the widely accepted record of 12 cycles during that time.This research enhances our understanding of historical solar activity,and underscores the importance of integrating diverse historical sources into modern analyses.展开更多
In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. U...In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.展开更多
To determine the cause(s)of perturbations seen in dayside equatorial ground magnetograms,we conducted a systematic survey of simultaneous ground-based and geosynchronous satellite-based observations during the 90-day ...To determine the cause(s)of perturbations seen in dayside equatorial ground magnetograms,we conducted a systematic survey of simultaneous ground-based and geosynchronous satellite-based observations during the 90-day period from December 1,2020 to February 28,2021.We examined Huancayo ground magnetometer observations from 14:00:00 to 20:00:00 UT each day,during which Huancayo passed through local noon.From those data we chose perturbation events selected on the basis of large(>20 nT)event amplitude and classified the selected events as responding primarily to solar wind pressure,or to variations in the north/south component of the interplanetary magnetic field(IMF Bz),or perhaps in part to both.The results show that an equivalent number of events were identified for each model during this 90-day period.Variations in the lagged solar wind dynamic pressure routinely correspond to nearly simultaneous sudden impulses recorded at both geosynchronous orbit and on the ground.Variations in IMF Bz produce erosion signatures at geosynchronous orbit and can correspond to ground events if lag times for reconnection to enhance convection in the magnetosphere are taken into account.展开更多
The three-dimensional displacements caused by ocean loading effects are significant enough to impact spatial geodetic measurements on sub-daily or longer timescales,particularly in the vertical direction.Currently,mos...The three-dimensional displacements caused by ocean loading effects are significant enough to impact spatial geodetic measurements on sub-daily or longer timescales,particularly in the vertical direction.Currently,most tide models incorporate the distribution of vertical displacement loading tides;however,their accuracy has not been assessed for the equatorial and Indian Ocean regions.Global Positioning System(GPS)observations provide high-precision data on sea-level changes,enabling the assessment of the accuracy and reliability of vertical displacement tide models.However,because the tidal period of the K_(2) constituent is almost identical to the orbital period of GPS constellations,the estimation of the K_(2) tidal constituent from GPS observations is not satisfactory.In this study,the principle of smoothness is employed to correct the systematic error in K_(2) estimates in GPS observations through quadratic fitting.Using the adjusted harmonic constants from 31 GPS stations for the equatorial and Indian Ocean,the accuracy of eight major constituents from five global vertical displacement tide models(FES2014,EOT11a,GOT4.10c,GOT4.8,and NAO.99b)is evaluated for the equatorial and Indian Ocean.The results indicate that the EOT11a and FES2014 models exhibit higher accuracy in the vertical displacement tide models for the equatorial and Indian Ocean,with root sum squares errors of 2.29 mm and 2.34 mm,res-pectively.Furthermore,a brief analysis of the vertical displacement tide distribution characteristics of the eight major constituents for the equatorial and Indian Ocean was conducted using the EOT11a model.展开更多
A recent study by Liu et al.(2020)suggested that due to the saturation of equatorially trapped planetary waves with different dynamical types,temporal periods,meridional and baroclinic modes,complex layer structures o...A recent study by Liu et al.(2020)suggested that due to the saturation of equatorially trapped planetary waves with different dynamical types,temporal periods,meridional and baroclinic modes,complex layer structures of vertical velocity shear and hence turbulent mixing could frequently occur in the thermocline of the eastern equatorial Pacific.We investigated the occurrence of the interior turbulent mixing as indicated by shear instabilities,above the Equatorial Undercurrent(EUC)core at three equatorial sites along 140°W,170°W,and 165°E,respectively,based mainly on data from the Tropical Atmosphere and Ocean(TAO)mooring array.We found that turbulent mixing bursts persisted in the thermocline of all three sites.Specifically,the interior turbulent mixing layers(ITMLs)could occur in probability of approximately 68%,53%,and 48%at the three sites,respectively.The overall occurrence probability shows obvious and similar biannual variations at 140°W and 170°W,which is higher in boreal from late summer to winter and lower in spring.Vertically,the ITMLs are primarily located above the EUC core and prevail in deeper(shallower)layers from late summer to winter(spring).Most ITMLs(70%)lasted for hours to 3 days,and a few of them(15%)for more than 7 days.The thicknesses of ITMLs were concentrated between 15 and 55 m.At 165°E,the vertical distribution of ITML occurrence probability was different from that at 140°W and 170°W,as it did not show a preference for depths;the durations of ITMLs are short(also from hours to several days)and their thicknesses were between 5 and 25 m.These properties,particularly the high occurrence probability,and short durations demonstrated the persistence of thermocline mixing in the western to eastern equatorial Pacific thermocline and confirmed the generation mechanism by persistent equatorial waves as well.展开更多
The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of...The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.展开更多
Based on the long-term buoy data from the Tropical Atmosphere Ocean ( TAO ) —array during the TOGA ( Tropical Ocean and Global Atmosphere ) Program (19801996), the propagation acting of the Equatorial planetary waves...Based on the long-term buoy data from the Tropical Atmosphere Ocean ( TAO ) —array during the TOGA ( Tropical Ocean and Global Atmosphere ) Program (19801996), the propagation acting of the Equatorial planetary waves on the Western Equatorial Pacific warm pool heat is analyzed. Results show that the zonal heat transmission in the Western Equatorial Pacific takes palace mainly in the subsurface water and spreads eastwards along the thermocline; while the seasonal westward-spreading heat change structure occurs in the mixed layers in the middle and western Pacific. The standing-form transmission in the western Pacific appears in the thermocline layer, while in the eastern pacific, it exists in the mixed layer as well as in the thermocline layer. The standing-form and eastward-spreading sign of zonal heat transmitting in the upper water is predominant and strong, and the westward sign is weak.The component force of Kelvin Equatorial wave pressure runs through the western and eastern Equatorial pacific, and transmits heat energy eastwards. And the heat transmitted by zonal current component occurs mostly in the western Pacific; The heat transmitted by the component force of Rossby wave pressure mainly appears in the eastern and middle areas of the Pacific, while the zonal current component transmitting occurs mainly in the western Pacific; Mixed-Rossby gravity wave’s action on the zonal current is stronger than that of the thermocline layer. In the mean state, the standing wave model of Equatorial Pacific up layer ocean temperature confines the transport of western Pacific warm pool heat to the eastern Pacific. Under abnormal conditions, the standing wave model of Equatorial Pacific up layer ocean temperature weakens, the eastwardly transmitting model enhances, and subsequently n^the El Ni o event occurs.展开更多
Previous studies have proposed that both the thermospheric neutral wind and the equatorial electrojet(EEJ)near sunset play important roles in the pre-reversal enhancement(PRE)mechanism.In this study,we have used obser...Previous studies have proposed that both the thermospheric neutral wind and the equatorial electrojet(EEJ)near sunset play important roles in the pre-reversal enhancement(PRE)mechanism.In this study,we have used observations made in the equatorial region of Southeast Asia during March–April and September–October in 2010–2013 to investigate influences of the eastward neutral wind and the EEJ on the PRE’s strength.Our analysis employs data collected by the Gravity Field and Steady-State Ocean Circulation Explorer(GOCE)satellite to determine the zonal(east-west direction)neutral wind at an altitude of~250 km(bottomside F region)at longitudes of 90°–130°E in the dusk sector.Three ionosondes,at Chumphon(dip lat.:3.0°N)in Thailand,at Bac Lieu(dip lat.:1.7°N)in Vietnam,and at Cebu(dip lat.:3.0°N)in Philippines,provided the data we have used to derive the PRE strength.Data from two magnetometers—at Phuket(dip lat.:0.1°S)in Thailand and at Kototabang(dip lat.:10.3°S)in Indonesia—were used to estimate the EEJ strength.Our study is focused particularly on days with magnetically quiet conditions.We have found that the eastward neutral wind and the EEJ are both closely correlated with the PRE;their cross-correlation coefficients with it are,respectively,0.42 and 0.47.Their relationship with each other is weaker:the cross-correlation coefficient between the eastward neutral wind and the EEJ is just 0.26.Our findings suggest that both the eastward neutral wind and the EEJ near sunset are involved in the PRE mechanism.Based on the weak relationship between these two parameters,however,they appear to be significantly independent of each other.Thus,the wind and the EEJ are likely to be influencing the PRE magnitude independently,their effects balancing each other.展开更多
Hydrographic and direct current measurements were made in the Eastern Equatorial Indian Ocean in May 2010 and April 2011 as part of the Eastern Indian Ocean Cruises(EIOC) organized by the South China Sea Institute of ...Hydrographic and direct current measurements were made in the Eastern Equatorial Indian Ocean in May 2010 and April 2011 as part of the Eastern Indian Ocean Cruises(EIOC) organized by the South China Sea Institute of Oceanology(SCSIO).Analyses of the shipdrift Acoustic Doppler Current Profiler(ADCP) data indicate that the equatorial currents observed in May 2010 are characterized by a strongly eastward surface current(Wyrtki Jets,WJs) with a maximum velocity of 0.9 m s 1,while that observed in April 2011 is weak and without a consistent direction.The strongly eastward WJ transports the surface water eastward,resulting in a deeper upper mixed layer,as shown in the temperature and salinity profiles.However,it was found that the Equatorial Undercurrent(EUC) in the Eastern Indian Ocean is strong in April 2011 and weak in May 2010.The EUC was located approximately at the position of the thermocline,and it had higher salinity(up to approximately 35.5 psu) than the upper and lower waters.展开更多
Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from simulation.However,occurrence characteristic...Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from simulation.However,occurrence characteristics of branching structure of equatorial plasma bubbles(BSEPBs)have not been well addressed.In this work,we used seven-years(2012-2018)of observations from two all-sky imagers to study occurrence of BSEPBs in detail.These data reveal a high incidence of BS in EPB cases;in particular,most EPBs occurring on days with geomagnetic disturbances exhibited BS.Periods when all EPBs exhibited BS increased significantly in the 2014 solar maximum.Occurrence times of BSEPBs varied with local time;most of the BSEPBs began to appear between 21:00 and 22:00 LT.During the solar maximum,some BSEPBs were observed after midnight.The data also reveal that BSEPBs are characterized primarily by two branches or three branches.Multi-branching appeared only in the solar maximum.EPB events with different coexisting branching structures increased from 2012 to 2014 and decreased from 2014 to 2018.These results strongly suggest that BSEPB occurrence is related to solar activity and geomagnetic activity,and thus provide a new perspective for future studies of EPBs as well as enriching our understanding of ionospheric irregularity.展开更多
The analyses of a data series obtained during TOGA- COARE show the existence of remarkable semi-diurnal intemal tides in the western equatorial Pacific Ocean around 1°45＇S, 156°E. Some characteristic parame...The analyses of a data series obtained during TOGA- COARE show the existence of remarkable semi-diurnal intemal tides in the western equatorial Pacific Ocean around 1°45＇S, 156°E. Some characteristic parameters of the internal tides are vertical wavenumber -1.6×10^-3 m^-1, horizontal wavenumber （wavelength） 3.3×10^-2 km^-1 （210 km）, vertical propagation speed -3.8 cm/s and horizontal propagation speed 2.0 m/s. The waveforms propagate downwards slantingly, that is, the wave energy transfers upwards slantingly. Depth-distribution of the＇rotary spectral levels is a saddle-shape. The depths of the trough and the deeper peaks are almost coincident with those of the south boundaries of the South Equatorial Current and the Equatorial Undercurrent, respectively. The mean orientation of the rotary spectral ellipse changes with depth： 30° from north to east at 40 m, and changes into 14° from east to south at 324 m, and generally, it points to northeastward, which indicates ＂that waves come from the southwest.展开更多
The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(E...The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(EAR)at Kototabang,Indonesia.The analysis shows that the occurrence of midnight hour EPBs was at its maximum during the low solar activity year 2010 and monotonically decreased thereafter with increasing solar activity.Details of the dependence of midnight hour EPB occurrence on solar activity were investigated using SAMI2 model simulation with a realistic input of E×B drift velocity data obtained from the CINDI-IVM onboard the C/NOFS satellite.Results obtained from term-by-term analysis of the flux tube integrated linear growth rate of RT instability indicate that the formation of a high flux tube electron content height gradient(steep vertical gradient)region at higher altitudes,due to the elevated F layer,is the key factor enhancing the growth rate of RT instability during low solar activity June solstices.Other factors are discussed in light of the relatively weak westward zonal electric field in the presence of the equatorward neutral wind and north-to-south transequatorial wind around the midnight hours of low solar activity June solstices.Also discussed are the initial seeding of RT instability by MSTIDs and how the threshold height required for EPB development varies with solar activity.展开更多
An obvious characteristic of the baroclinic large-scale motions in the equatorial ocean is that the meridional scale H of motion is far smaller than the zonal scale L. The scaling of motion carefully with this strikin...An obvious characteristic of the baroclinic large-scale motions in the equatorial ocean is that the meridional scale H of motion is far smaller than the zonal scale L. The scaling of motion carefully with this striking characteristic in this paper results in two conclusions, i. e., the Coriolis terms associated with the horizontal component of the rotation vector cannot be neglected in the governing equations; and the use of the absence of heating is not suitable to the equatorial region. In this paper the equatorial β-plane nondimensional governing equations with the small parametersδ_0 andδ_1 have been Obtained.展开更多
The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional win...The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional wind at 925 h Pa.The first mode(EOF1)exhibits an in-phase relationship among different CEF channels over the AAM region,which has received much attention owing to its tight linkage with ENSO.By contrast,the second mode(EOF2)possesses an out-of-phase relationship between the Bay of Bengal(BOB)CEF(90°E)and Australian CEF,among which the New Guinea CEF near 150°E shows the most significant opposite correlation with the BOB CEF.Observational and numerical model results suggest that the equatorially asymmetric heat source(sink)over the western(eastern)Maritime Continent,closely associated with the in-situ sea surface temperature anomaly,can induce cross-equatorial northerly(southerly)flow into the heating hemisphere,which dominates the out-of-phase relationship between the BOB and New Guinea CEFs.Furthermore,an equatorially symmetric heating over the central Pacific may indirectly change the CEFs by modulating the zonal atmospheric circulation near the Maritime Continent.展开更多
Solar radiation penetration in the upper ocean is strongly modulated by phytoplankton, which impacts the upper ocean temperature structure, especially in the regions abundant with phytoplankton. In the paper, a new so...Solar radiation penetration in the upper ocean is strongly modulated by phytoplankton, which impacts the upper ocean temperature structure, especially in the regions abundant with phytoplankton. In the paper, a new solar radiation penetration scheme, based on the concentration of chlorophyll-a, was introduced into the LASG/IAP （State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics） Climate system Ocean Model （LICOM）. By comparing the simulations using this new scheme with those using the old scheme that included the constant e-folding attenuation depths in LICOM, it was found that the sea surface temperature （SST） and circulation in the central and eastern equatorial Pacific were both sensitive to the amount of phytoplankton present. Distinct from other regions, the increase of chlorophyll-a concentration would lead to SST decrease in the central and eastern equatorial Pacific. The higher chlorophyll-a concentration at the equator in comparison to the off-equator regions can enlarge the subsurface temperature gradient, which in turn strengthens the upper current near the equator and induces an enhancing upwelling. The enhancing upwelling can then lead to a decrease in the SST in the central and eastern equatorial Pacific. The results of these two sensitive experiments testify to the fact that the meridional gradient in the chlorophyll-a concentration can result in an enhancement in the upper current and a decrease in the SST, along with the observation that a high chlorophyll-a concentration at the equator is one of the predominant reasons leading to a decrease in the SST. This study points out that these results can be qualitatively different simply because of the choice of the solar radiation penetration schemes for comparison. This can help explain previously reported contradictory conclusions.展开更多
A survey was conducted in the equatorial area of Indian Ocean for a better understanding of the dynamics of hook depth distribution of pelagic longline fishery. We determined the relationship between hook depth and ve...A survey was conducted in the equatorial area of Indian Ocean for a better understanding of the dynamics of hook depth distribution of pelagic longline fishery. We determined the relationship between hook depth and vertical shear of current coefficieney, wind speed, hook position code, sine of wind angle, sine of angle of attack and weight of messenger weight. We identified the hook depth models by the analysis of covariance with a general linear model. The results showed that the wind effect on the hook depth can be ignored from October to November in the survey area; the surface current effect on the hook depth can be ignored; the equato- rial undercurrent is the key factor for the hook depth in Indian Ocean; and there is a negative correlation between the hook depth and vertical shear of current and angle of attack. It was also found that the deeper the hook was set, the higher hook depth shoaling was. The proposed model improves the accuracy of the prediction of hook depth, which can be used to estimate the vertical distribution of pelagic fish in water column.展开更多
A severe drought occurred in East China(EC)from August to October 2019 against a background of long-term significant warming and caused widespread impacts on agriculture and society,emphasizing the urgent need to unde...A severe drought occurred in East China(EC)from August to October 2019 against a background of long-term significant warming and caused widespread impacts on agriculture and society,emphasizing the urgent need to understand the mechanism responsible for this drought and its linkage to global warming.Our results show that the warm central equatorial Pacific(CEP)sea surface temperature(SST)and anthropogenic warming were possibly responsible for this drought event.The warm CEP SST anomaly resulted in an anomalous cyclone over the western North Pacific,where enhanced northerly winds in the northwestern sector led to decreased water vapor transport from the South China Sea and enhanced descending air motion,preventing local convection and favoring a precipitation deficiency over EC.Model simulations in the Community Earth System Model Large Ensemble Project confirmed the physical connection between the warm CEP SST anomaly and the drought in EC.The extremely warm CEP SST from August to October 2019,which was largely the result of natural internal variability,played a crucial role in the simultaneous severe drought in EC.The model simulations showed that anthropogenic warming has greatly increased the frequency of extreme droughts in EC.They indicated an approximate twofold increase in extremely low rainfall events,high temperature events,and concurrently dry and hot events analogous to the event in 2019.Therefore,the persistent severe drought over EC in 2019 can be attributed to the combined impacts of warm CEP SST and anthropogenic warming.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42376071,42006056)the Special Fund of South China Sea Institute of Oceanol-ogy of the Chinese Academy of Sciences(No.SCSIO 2024QY02)the Chinese Academy of Sciences Pro-ject(No.Y4SL021).
文摘The Equatorial Atlantic Ocean,a region crucial to understanding Earth’s tectonic processes and advancing the theory of plate tectonics,remains the focus of extensive research aimed at unraveling its evolution.However,its complex structural setting and contentious formation timeline have posed significant challenges.Through a comprehensive review of contemporary scientific litera-ture,we have identified three distinct phases for its evolution:pre-breakup,syn-breakup,and post-breakup,providing more detailed in-sights into the tectonic evolution of the Equatorial Atlantic.Prior to 110 Myr,the African and South American Plates underwent stretching predominantly from North to South,with the emergence of the Parana plume.This condition has led to the formation of nu-merous fracture zones and a triple junction.During the syn-breakup phase,spanning from 110 Myr to 90 Myr,the central region of the Equatorial Atlantic fully opened up,establishing a connection between the northern and southern waterways.However,the develop-ment of multiple ridge segments separated by numerous fracture zones in the central Equatorial Atlantic exhibited considerable com-plexity.The underlying causes for these complex structural formations remain elusive.Following the Chicxulub meteorite impact around 66 Myr and the emergence of the Sierra Leone hotspot,a pair of oceanic plateau‘twins’and a series of seamount chains were formed as a result of mantle plume tails.Consequently,the timeline of the Equatorial Atlantic’s tectonic evolution has gradually be-come clearer.However,due to the extensive timescale and the multitude of events involved in its formation,disputes about the precise-timing of various events still remain.The evolution of the Equatorial Atlantic has witnessed numerous ridge propagations,hotspot formations,and meteorite impacts,highlighting the need for further investigation into their interactions.The absence of identified magnetic isochrons in the Equatorial region emphasizes the urgency of additional exploration and analysis of its geological and geo-physical data.
基金JSPS KAKENHI Grant Number16H06286 supports global GNSS ionospheric maps (TEC,ROTI,and detrended TEC maps) developed by the Institute for SpaceEarth Environmental Research (ISEE) of Nagoya Universitysupport of the 2024 JASSO Follow-up Research Fellowship Program for a 90-day visiting research at the Institute for Space-Earth Environmental Research (ISEE),Nagoya University+3 种基金the support received from Telkom University under the“Skema Penelitian Terapan Periode I Tahun Anggaran 2024”the Memorandum of Understanding for Research Collaboration on Regional Ionospheric Observation (No:092/SAM3/TE-DEK/2021)the National Institute of Information and Communications Technology (NICT) International Exchange Program 2024-2025(No.2024-007)support for a one-year visiting research at Hokkaido University
文摘This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.
基金the Ministry of Higher Education(KPT)Malaysia for the MyBrainSc program.Idahwati Sarudin was supported by Universiti Sains Malaysia through a Short-Term Grant(Project No.304/PFIZIK/6315730)Nurul Shazana Abdul Hamid received funding from Universiti Kebangsaan Malaysia for funding this work through a University Research Grant(Grant No.GUP-2023-048)。
文摘Thermospheric neutral winds(TNWs)refer to the neutral gases in the thermosphere circulating as tides,which play a crucial role in the dynamics of the thermosphere-ionosphere system(TIS).Global geospace neutral winds,particularly over the magnetic equator,have been a subject of study for several decades.However,despite the known importance of neutral winds,a comprehensive understanding and characterization of the winds is still lacking.Various ground-based and satellite missions have provided valuable information on the contribution of neutral winds to the global atmospheric dynamics.However,efforts in the global monitoring of neutral winds are still lacking,and the drivers behind the behavior of TNWs as well as their influence on the TIS remain incomplete.To address these knowledge gaps in the global circulation of TNWs,it is crucial to develop a deep understanding of the neutral wind characteristics over different regions.The low-latitude equatorial region in particular has been observed to exert complex influences on TNWs because of the unique effects of the Earth’s magnetic field at the dip equator.Studying neutral winds over this region will provide valuable insights into the unique dynamics and processes that occur in this region,thereby enhancing our understanding of their role in the overall dynamics of the TIS.Additionally,through empirical observations,an improved ability to accurately model and predict the behavior of this region can be achieved.This review article addresses challenges in understanding equatorial winds by reviewing historical measurements,current missions,and the interactions of ionospheric and thermospheric phenomena,emphasizing the need for comprehensive measurements to improve global atmospheric dynamics and weather forecasting.
基金supported by the National Natural Science Foundation of China (42388101)the CAS Youth Interdisciplinary Team (JCTD-2021-05)funded by the Youth Innovation Promotion Association, Chinese Academy of Sciences.
文摘Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while also deepening our knowledge of stellar physics and solar system dynamics.Determining the solar cycles between 1600 and 1700-especially the post-1645 Maunder Minimum,characterized by significantly reduced solar activity-poses challenges to existing solar activity proxies.This study utilizes a new red equatorial auroral catalog from ancient Korean texts to establish solar cycle patterns from 1623 to 1700.Remarkably,a further reevaluation of the solar cycles between 1610 and 1755 identified a total of 13 cycles,diverging from the widely accepted record of 12 cycles during that time.This research enhances our understanding of historical solar activity,and underscores the importance of integrating diverse historical sources into modern analyses.
基金supported by the National Key R&D Program of China (Grant No. 2022YFF0503700)the special funds of Hubei Luojia Laboratory (220100011)+1 种基金Chao Xiong is supported by the ISSI-BJ project, “the electromagnetic data validation and scientific application research based on CSES satellite”ISSI/ISSI-BJ project “Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction”。
文摘In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.
文摘To determine the cause(s)of perturbations seen in dayside equatorial ground magnetograms,we conducted a systematic survey of simultaneous ground-based and geosynchronous satellite-based observations during the 90-day period from December 1,2020 to February 28,2021.We examined Huancayo ground magnetometer observations from 14:00:00 to 20:00:00 UT each day,during which Huancayo passed through local noon.From those data we chose perturbation events selected on the basis of large(>20 nT)event amplitude and classified the selected events as responding primarily to solar wind pressure,or to variations in the north/south component of the interplanetary magnetic field(IMF Bz),or perhaps in part to both.The results show that an equivalent number of events were identified for each model during this 90-day period.Variations in the lagged solar wind dynamic pressure routinely correspond to nearly simultaneous sudden impulses recorded at both geosynchronous orbit and on the ground.Variations in IMF Bz produce erosion signatures at geosynchronous orbit and can correspond to ground events if lag times for reconnection to enhance convection in the magnetosphere are taken into account.
基金The Shandong Provincial Natural Science Foundation under contract No.ZR2023QD045the National Natural Science Foundation of China under contract Nos 42406026,42076024 and 42106032supported by the Taishan Scholar Program under contract No.tstp20221148。
文摘The three-dimensional displacements caused by ocean loading effects are significant enough to impact spatial geodetic measurements on sub-daily or longer timescales,particularly in the vertical direction.Currently,most tide models incorporate the distribution of vertical displacement loading tides;however,their accuracy has not been assessed for the equatorial and Indian Ocean regions.Global Positioning System(GPS)observations provide high-precision data on sea-level changes,enabling the assessment of the accuracy and reliability of vertical displacement tide models.However,because the tidal period of the K_(2) constituent is almost identical to the orbital period of GPS constellations,the estimation of the K_(2) tidal constituent from GPS observations is not satisfactory.In this study,the principle of smoothness is employed to correct the systematic error in K_(2) estimates in GPS observations through quadratic fitting.Using the adjusted harmonic constants from 31 GPS stations for the equatorial and Indian Ocean,the accuracy of eight major constituents from five global vertical displacement tide models(FES2014,EOT11a,GOT4.10c,GOT4.8,and NAO.99b)is evaluated for the equatorial and Indian Ocean.The results indicate that the EOT11a and FES2014 models exhibit higher accuracy in the vertical displacement tide models for the equatorial and Indian Ocean,with root sum squares errors of 2.29 mm and 2.34 mm,res-pectively.Furthermore,a brief analysis of the vertical displacement tide distribution characteristics of the eight major constituents for the equatorial and Indian Ocean was conducted using the EOT11a model.
基金Supported by the National Natural Science Foundation of China(NSFC)(No.41730534)the Laoshan Laboratory Science and Technology Innovation Program(No.LSKJ 202202502)+1 种基金the NSFC(Nos.41976012,42090044)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB42000000)。
文摘A recent study by Liu et al.(2020)suggested that due to the saturation of equatorially trapped planetary waves with different dynamical types,temporal periods,meridional and baroclinic modes,complex layer structures of vertical velocity shear and hence turbulent mixing could frequently occur in the thermocline of the eastern equatorial Pacific.We investigated the occurrence of the interior turbulent mixing as indicated by shear instabilities,above the Equatorial Undercurrent(EUC)core at three equatorial sites along 140°W,170°W,and 165°E,respectively,based mainly on data from the Tropical Atmosphere and Ocean(TAO)mooring array.We found that turbulent mixing bursts persisted in the thermocline of all three sites.Specifically,the interior turbulent mixing layers(ITMLs)could occur in probability of approximately 68%,53%,and 48%at the three sites,respectively.The overall occurrence probability shows obvious and similar biannual variations at 140°W and 170°W,which is higher in boreal from late summer to winter and lower in spring.Vertically,the ITMLs are primarily located above the EUC core and prevail in deeper(shallower)layers from late summer to winter(spring).Most ITMLs(70%)lasted for hours to 3 days,and a few of them(15%)for more than 7 days.The thicknesses of ITMLs were concentrated between 15 and 55 m.At 165°E,the vertical distribution of ITML occurrence probability was different from that at 140°W and 170°W,as it did not show a preference for depths;the durations of ITMLs are short(also from hours to several days)and their thicknesses were between 5 and 25 m.These properties,particularly the high occurrence probability,and short durations demonstrated the persistence of thermocline mixing in the western to eastern equatorial Pacific thermocline and confirmed the generation mechanism by persistent equatorial waves as well.
文摘The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.
文摘Based on the long-term buoy data from the Tropical Atmosphere Ocean ( TAO ) —array during the TOGA ( Tropical Ocean and Global Atmosphere ) Program (19801996), the propagation acting of the Equatorial planetary waves on the Western Equatorial Pacific warm pool heat is analyzed. Results show that the zonal heat transmission in the Western Equatorial Pacific takes palace mainly in the subsurface water and spreads eastwards along the thermocline; while the seasonal westward-spreading heat change structure occurs in the mixed layers in the middle and western Pacific. The standing-form transmission in the western Pacific appears in the thermocline layer, while in the eastern pacific, it exists in the mixed layer as well as in the thermocline layer. The standing-form and eastward-spreading sign of zonal heat transmitting in the upper water is predominant and strong, and the westward sign is weak.The component force of Kelvin Equatorial wave pressure runs through the western and eastern Equatorial pacific, and transmits heat energy eastwards. And the heat transmitted by zonal current component occurs mostly in the western Pacific; The heat transmitted by the component force of Rossby wave pressure mainly appears in the eastern and middle areas of the Pacific, while the zonal current component transmitting occurs mainly in the western Pacific; Mixed-Rossby gravity wave’s action on the zonal current is stronger than that of the thermocline layer. In the mean state, the standing wave model of Equatorial Pacific up layer ocean temperature confines the transport of western Pacific warm pool heat to the eastern Pacific. Under abnormal conditions, the standing wave model of Equatorial Pacific up layer ocean temperature weakens, the eastwardly transmitting model enhances, and subsequently n^the El Ni o event occurs.
基金supported by the program of Follow-up Research Guidance of Japan Student Services Organization(JASSO)in 2019the Indonesian Ministry of Research and Technology and National Research and Innovative Agency(Kementerian RISTEK-BRIN)through the program of Pusat Unggulan Iptek(PUI)in 2019+4 种基金the Space Science Center of LAPAN through a research grant program in 2020support from JSPS KAKENHI Grants 18H01270,18H04446,and 17KK0095JRPs-LEAD with DFGpartially supported by JSPS KAKENHI Grant Number 20H00197supported by the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(grant number B05F630018)。
文摘Previous studies have proposed that both the thermospheric neutral wind and the equatorial electrojet(EEJ)near sunset play important roles in the pre-reversal enhancement(PRE)mechanism.In this study,we have used observations made in the equatorial region of Southeast Asia during March–April and September–October in 2010–2013 to investigate influences of the eastward neutral wind and the EEJ on the PRE’s strength.Our analysis employs data collected by the Gravity Field and Steady-State Ocean Circulation Explorer(GOCE)satellite to determine the zonal(east-west direction)neutral wind at an altitude of~250 km(bottomside F region)at longitudes of 90°–130°E in the dusk sector.Three ionosondes,at Chumphon(dip lat.:3.0°N)in Thailand,at Bac Lieu(dip lat.:1.7°N)in Vietnam,and at Cebu(dip lat.:3.0°N)in Philippines,provided the data we have used to derive the PRE strength.Data from two magnetometers—at Phuket(dip lat.:0.1°S)in Thailand and at Kototabang(dip lat.:10.3°S)in Indonesia—were used to estimate the EEJ strength.Our study is focused particularly on days with magnetically quiet conditions.We have found that the eastward neutral wind and the EEJ are both closely correlated with the PRE;their cross-correlation coefficients with it are,respectively,0.42 and 0.47.Their relationship with each other is weaker:the cross-correlation coefficient between the eastward neutral wind and the EEJ is just 0.26.Our findings suggest that both the eastward neutral wind and the EEJ near sunset are involved in the PRE mechanism.Based on the weak relationship between these two parameters,however,they appear to be significantly independent of each other.Thus,the wind and the EEJ are likely to be influencing the PRE magnitude independently,their effects balancing each other.
基金supported by the Ministry of Science and Technology (MOST) of China(Grant No.2011CB403504)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant Nos.KZCX2-EW-208 and KZCX2-YW-Q11-02)the National Natural Science Foundationof China(Grant No.41076009)
文摘Hydrographic and direct current measurements were made in the Eastern Equatorial Indian Ocean in May 2010 and April 2011 as part of the Eastern Indian Ocean Cruises(EIOC) organized by the South China Sea Institute of Oceanology(SCSIO).Analyses of the shipdrift Acoustic Doppler Current Profiler(ADCP) data indicate that the equatorial currents observed in May 2010 are characterized by a strongly eastward surface current(Wyrtki Jets,WJs) with a maximum velocity of 0.9 m s 1,while that observed in April 2011 is weak and without a consistent direction.The strongly eastward WJ transports the surface water eastward,resulting in a deeper upper mixed layer,as shown in the temperature and salinity profiles.However,it was found that the Equatorial Undercurrent(EUC) in the Eastern Indian Ocean is strong in April 2011 and weak in May 2010.The EUC was located approximately at the position of the thermocline,and it had higher salinity(up to approximately 35.5 psu) than the upper and lower waters.
基金supported by the Youth Science and Technology Innovation Foundation of NSSCthe International Partnership Program of Chinese Academy of Sciences(183311KYSB20200003)+1 种基金the National Natural Science Foundation of China(41831073 and 42004138)the Open Research Project of Large Research Infrastructures of CAS–“Study on the interaction between low/mid-latitude atmosphere and ionosphere based on the Chinese Meridian Project”。
文摘Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from simulation.However,occurrence characteristics of branching structure of equatorial plasma bubbles(BSEPBs)have not been well addressed.In this work,we used seven-years(2012-2018)of observations from two all-sky imagers to study occurrence of BSEPBs in detail.These data reveal a high incidence of BS in EPB cases;in particular,most EPBs occurring on days with geomagnetic disturbances exhibited BS.Periods when all EPBs exhibited BS increased significantly in the 2014 solar maximum.Occurrence times of BSEPBs varied with local time;most of the BSEPBs began to appear between 21:00 and 22:00 LT.During the solar maximum,some BSEPBs were observed after midnight.The data also reveal that BSEPBs are characterized primarily by two branches or three branches.Multi-branching appeared only in the solar maximum.EPB events with different coexisting branching structures increased from 2012 to 2014 and decreased from 2014 to 2018.These results strongly suggest that BSEPB occurrence is related to solar activity and geomagnetic activity,and thus provide a new perspective for future studies of EPBs as well as enriching our understanding of ionospheric irregularity.
基金This paper is supported by the National Natural Science Foundation of China(Projects under contracts No.49676275,49976002,40506007)Microwave Imaging National Key Laboratory Foundation(No.51442020103JW1002).
文摘The analyses of a data series obtained during TOGA- COARE show the existence of remarkable semi-diurnal intemal tides in the western equatorial Pacific Ocean around 1°45＇S, 156°E. Some characteristic parameters of the internal tides are vertical wavenumber -1.6×10^-3 m^-1, horizontal wavenumber （wavelength） 3.3×10^-2 km^-1 （210 km）, vertical propagation speed -3.8 cm/s and horizontal propagation speed 2.0 m/s. The waveforms propagate downwards slantingly, that is, the wave energy transfers upwards slantingly. Depth-distribution of the＇rotary spectral levels is a saddle-shape. The depths of the trough and the deeper peaks are almost coincident with those of the south boundaries of the South Equatorial Current and the Equatorial Undercurrent, respectively. The mean orientation of the rotary spectral ellipse changes with depth： 30° from north to east at 40 m, and changes into 14° from east to south at 324 m, and generally, it points to northeastward, which indicates ＂that waves come from the southwest.
基金partly supported by the National Natural Science Foundation of China(42020104002)by a Postdoctoral Fellowship at the Institute of Geology and Geophysics,Chinese Academy of Sciences(IGGCAS)partially supported by JSPS KAKENHI Grant Number 20H00197。
文摘The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(EAR)at Kototabang,Indonesia.The analysis shows that the occurrence of midnight hour EPBs was at its maximum during the low solar activity year 2010 and monotonically decreased thereafter with increasing solar activity.Details of the dependence of midnight hour EPB occurrence on solar activity were investigated using SAMI2 model simulation with a realistic input of E×B drift velocity data obtained from the CINDI-IVM onboard the C/NOFS satellite.Results obtained from term-by-term analysis of the flux tube integrated linear growth rate of RT instability indicate that the formation of a high flux tube electron content height gradient(steep vertical gradient)region at higher altitudes,due to the elevated F layer,is the key factor enhancing the growth rate of RT instability during low solar activity June solstices.Other factors are discussed in light of the relatively weak westward zonal electric field in the presence of the equatorward neutral wind and north-to-south transequatorial wind around the midnight hours of low solar activity June solstices.Also discussed are the initial seeding of RT instability by MSTIDs and how the threshold height required for EPB development varies with solar activity.
基金the National Natural Science Foundation of China under contract! No. 49676282.
文摘An obvious characteristic of the baroclinic large-scale motions in the equatorial ocean is that the meridional scale H of motion is far smaller than the zonal scale L. The scaling of motion carefully with this striking characteristic in this paper results in two conclusions, i. e., the Coriolis terms associated with the horizontal component of the rotation vector cannot be neglected in the governing equations; and the use of the absence of heating is not suitable to the equatorial region. In this paper the equatorial β-plane nondimensional governing equations with the small parametersδ_0 andδ_1 have been Obtained.
基金jointly supported by the National Key Research and Development Program of China[grant number 2016YFA0600601]the National Natural Science Foundation of China[grant numbers 42030601 and 41875087]。
文摘The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional wind at 925 h Pa.The first mode(EOF1)exhibits an in-phase relationship among different CEF channels over the AAM region,which has received much attention owing to its tight linkage with ENSO.By contrast,the second mode(EOF2)possesses an out-of-phase relationship between the Bay of Bengal(BOB)CEF(90°E)and Australian CEF,among which the New Guinea CEF near 150°E shows the most significant opposite correlation with the BOB CEF.Observational and numerical model results suggest that the equatorially asymmetric heat source(sink)over the western(eastern)Maritime Continent,closely associated with the in-situ sea surface temperature anomaly,can induce cross-equatorial northerly(southerly)flow into the heating hemisphere,which dominates the out-of-phase relationship between the BOB and New Guinea CEFs.Furthermore,an equatorially symmetric heating over the central Pacific may indirectly change the CEFs by modulating the zonal atmospheric circulation near the Maritime Continent.
文摘Solar radiation penetration in the upper ocean is strongly modulated by phytoplankton, which impacts the upper ocean temperature structure, especially in the regions abundant with phytoplankton. In the paper, a new solar radiation penetration scheme, based on the concentration of chlorophyll-a, was introduced into the LASG/IAP （State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics） Climate system Ocean Model （LICOM）. By comparing the simulations using this new scheme with those using the old scheme that included the constant e-folding attenuation depths in LICOM, it was found that the sea surface temperature （SST） and circulation in the central and eastern equatorial Pacific were both sensitive to the amount of phytoplankton present. Distinct from other regions, the increase of chlorophyll-a concentration would lead to SST decrease in the central and eastern equatorial Pacific. The higher chlorophyll-a concentration at the equator in comparison to the off-equator regions can enlarge the subsurface temperature gradient, which in turn strengthens the upper current near the equator and induces an enhancing upwelling. The enhancing upwelling can then lead to a decrease in the SST in the central and eastern equatorial Pacific. The results of these two sensitive experiments testify to the fact that the meridional gradient in the chlorophyll-a concentration can result in an enhancement in the upper current and a decrease in the SST, along with the observation that a high chlorophyll-a concentration at the equator is one of the predominant reasons leading to a decrease in the SST. This study points out that these results can be qualitatively different simply because of the choice of the solar radiation penetration schemes for comparison. This can help explain previously reported contradictory conclusions.
基金funded by Ministry of Agriculture of China under Project of Fishery Exploration in High Seasin 2006 (No. Z06-43)the National High Technology Research and Development Program of China (No. 2012AA092302)+1 种基金Specialized research fund for the doctoral program of higher education (No. 20113104110004)Shanghai Municipal Education Commission Innovation Project (No. 12ZZ168)
文摘A survey was conducted in the equatorial area of Indian Ocean for a better understanding of the dynamics of hook depth distribution of pelagic longline fishery. We determined the relationship between hook depth and vertical shear of current coefficieney, wind speed, hook position code, sine of wind angle, sine of angle of attack and weight of messenger weight. We identified the hook depth models by the analysis of covariance with a general linear model. The results showed that the wind effect on the hook depth can be ignored from October to November in the survey area; the surface current effect on the hook depth can be ignored; the equato- rial undercurrent is the key factor for the hook depth in Indian Ocean; and there is a negative correlation between the hook depth and vertical shear of current and angle of attack. It was also found that the deeper the hook was set, the higher hook depth shoaling was. The proposed model improves the accuracy of the prediction of hook depth, which can be used to estimate the vertical distribution of pelagic fish in water column.
基金the National Key R&D Program(Grant No.2018YFC1505904)the National Natural Science Foundation of China(Grant Nos.41830969 and 41705052)the Basic Scientific Research and Operation Foundation of CAMS(Grant No.2018Z006).
文摘A severe drought occurred in East China(EC)from August to October 2019 against a background of long-term significant warming and caused widespread impacts on agriculture and society,emphasizing the urgent need to understand the mechanism responsible for this drought and its linkage to global warming.Our results show that the warm central equatorial Pacific(CEP)sea surface temperature(SST)and anthropogenic warming were possibly responsible for this drought event.The warm CEP SST anomaly resulted in an anomalous cyclone over the western North Pacific,where enhanced northerly winds in the northwestern sector led to decreased water vapor transport from the South China Sea and enhanced descending air motion,preventing local convection and favoring a precipitation deficiency over EC.Model simulations in the Community Earth System Model Large Ensemble Project confirmed the physical connection between the warm CEP SST anomaly and the drought in EC.The extremely warm CEP SST from August to October 2019,which was largely the result of natural internal variability,played a crucial role in the simultaneous severe drought in EC.The model simulations showed that anthropogenic warming has greatly increased the frequency of extreme droughts in EC.They indicated an approximate twofold increase in extremely low rainfall events,high temperature events,and concurrently dry and hot events analogous to the event in 2019.Therefore,the persistent severe drought over EC in 2019 can be attributed to the combined impacts of warm CEP SST and anthropogenic warming.
