Saharan dust represents more than 50%of the total desert dust emitted around the globe and its radiative effect significantly affects the atmospheric circulation at a continental scale.Previous studies on dust vertica...Saharan dust represents more than 50%of the total desert dust emitted around the globe and its radiative effect significantly affects the atmospheric circulation at a continental scale.Previous studies on dust vertical distribution and the Saharan Air Layer(SAL)showed some shortcomings that could be attributed to imperfect representation of the effects of deep convection and scavenging.The authors investigate here the role of deep convective transport and scavenging on the vertical distribution of mineral dust over Western Africa.Using multi-year(2006-2010)simulations performed with the variable-resolution(zoomed)version of the LMDZ climate model.Simulations are compared with aerosol amounts recorded by the Aerosol Robotic Network(AERONET)and with vertical profiles of the Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP)measurements.LMDZ allows a thorough examination of the respective roles of deep convective transport,convective and stratiform scavenging,boundary layer transport,and advection processes on the vertical mineral dust distribution over Western Africa.The comparison of simulated dust Aerosol Optical Depth(AOD)and distribution with measurements suggest that scavenging in deep convection and subsequent re-evaporation of dusty rainfall in the lower troposphere are critical processes for explaining the vertical distribution of desert dust.These processes play a key role in maintaining a well-defined dust layer with a sharp transition at the top of the SAL and in establishing the seasonal cycle of dust distribution.This vertical distribution is further reshaped offshore in the Inter-Tropical Convergence Zone(ITCZ)over the Atlantic Ocean by marine boundary layer turbulent and convective transport and wet deposition at the surface.展开更多
Understanding the potential vertical distribution of bigeye tuna(Thunnus obesus) is necessary to understand the catch rate fluctuations and the stock assessment of bigeye tuna. To characterize the potential vertical d...Understanding the potential vertical distribution of bigeye tuna(Thunnus obesus) is necessary to understand the catch rate fluctuations and the stock assessment of bigeye tuna. To characterize the potential vertical distribution of this fish while foraging and determine the influences of the distribution on longline efficiency in the tropical Atlantic Ocean, the catch per unit effort(CPUE) data were compiled from the International Commission for the Conservation of Atlantic Tunas and the Argo buoy data were downloaded from the Argo data center. The raw Argo buoy data were processed by data mining methods. The CPUE was standardized by support vector machine before analysis. We assumed the depths with the upper and lower limits of the optimum water temperatures of 15℃ and 9℃ as the preferred swimming depth, while the lower limit of the temperature(12℃) associated with the highest hooking rate as the preferred foraging depth(D12) of bigeye tuna during the daytime in the Atlantic Ocean. The preferred swimming depth and foraging depth range in the daytime were assessed by plotting the isobath based on Argo buoy data. The preferred swimming depth and vertical structure of the water column were identified to investigate the spatial effects on the CPUE by using a generalized additive model(GAM). The empirical cumulative distribution function was used to assess the relationship between the spatial distribution of CPUE and the depth of 12℃ isolines and thermocline. The results indicate that 1) the preferred swimming depth of bigeye tuna in the tropical Atlantic is from 100 m to 400 m and displays spatial variation;2) the preferred foraging depth of bigeye tuna is between 190 and 300 m and below the thermocline;3) the number of CPUEs peaks at a relative depth of 30 –50 m(difference between the 12℃ isolines and the lower boundary of the thermocline);and 4) most CPUEs are within the lower depth boundary of the thermocline levels(LDBT) which is from 160 m to 230 m. GAM analysis indicates that the general relationship between the nominal CPUE and LDBT is characterized by a dome shape and peaks at approximately 190 m. The oceanographic features influence the habitat of tropical pelagic fish and fisheries. Argo buoy data can be an important tool to describe the habitat of oceanic fish. Our results provide new insights into how oceanographic features influence the habitat of tropical pelagic fish and fisheries and how fisheries exploit these fish using a new tool(Argo profile data).展开更多
Although the microbial diversity of the Indian Ocean has been extensively investigated,little is known about the community composition of microbes in the Southern Indian Ocean.In the present study,we divided 60 water ...Although the microbial diversity of the Indian Ocean has been extensively investigated,little is known about the community composition of microbes in the Southern Indian Ocean.In the present study,we divided 60 water column samples on the Ninety-East Ridge(NER)into fi ve water masses according to the temperature-salinity curves.We presented,for the fi rst time,a full description of the microbial biodiversity on NER through high-throughput amplicon sequencing approach,including bacteria,archaea,and fungi.We found that bacteria exhibited higher richness and diversity than archaea and fungi across the water masses on NER.More importantly,each water mass on NER featured distinct prokaryotic microbial communities,as indicated by the results of non-metric multidimensional scaling.In contrast,fungi were eurybathic across the water masses.Redundancy analysis results demonstrated that environmental factors might play a pivotal role in the formation and stability of prokaryotic communities in each water mass,especially that of archaea.In addition,indicator species might be used as fi ngerprints to identify corresponding water masses on NER.These results provide new insights into the vertical distribution,structure,and diversity of microorganisms on NER from the perspective of water mass.展开更多
Based on the Stratospheric Aerosol and Gas Experiment (SAGE) II and the Halogen Occultation Ex-periment (HALOE) ozone profiles and the Total Ozone Mapping Spectrometer (TOMS) total ozone data sets,the characteristics ...Based on the Stratospheric Aerosol and Gas Experiment (SAGE) II and the Halogen Occultation Ex-periment (HALOE) ozone profiles and the Total Ozone Mapping Spectrometer (TOMS) total ozone data sets,the characteristics and variations of the vertical distribution of stratospheric ozone covering the latitude bands of 50oN±5oN,40oN±5oN,30oN±5oN,and 20oN±5oN and the longitude range of 75-135oE are investigated.The results indicate that the ozone distribution pattern over China not only has general behaviors,but also has particular char-acteristics.In view of the situation that ozone distribu-tions have substantial deviation from zonal symmetry in northern China,the differences of the vertical ozone dis-tribution between the east and the west part of northern China are studied.The results indicate that during winter,spring,and autumn,in the latitude bands of 50oN±5oN,40oN±5oN,ozone concentrations in the eastern part (105 -135oE) are obviously higher than those of the west (75-105oE) at the altitudes of ozone density maximum and below;during summer,in the latitude band of 50oN±5oN,the east-west ozone profile difference is small,but in the latitude band of 40oN±5oN,the east-west total ozone difference becomes as large as 14.0 DU,and the east-west ozone profile difference mainly exists in the lowermost stratosphere and troposphere.展开更多
Three economic plants from the loess gully areas in China to explore the changing vertical distribution characteristics of soil organic carbon.The results showed that:(1) with the increase of depth,the average SOC con...Three economic plants from the loess gully areas in China to explore the changing vertical distribution characteristics of soil organic carbon.The results showed that:(1) with the increase of depth,the average SOC content of economic plants decreased from 13.98 to 1.39 g/kg on the 0-100 cm soil profile,in the form of a power function;(2) the constructed depth spatial distribution models for different plants could help accurately assess the spatial distribution pattern of soil organic carbon;(3) compared with traditional agricultural planting,the carbon sink function for walnut and grape at a soil depth of 100 cm increased by 92.8±8.98 t/hm^(2) and 45.7±7.7 t/hm^(2),respectively.The adjustment of agricultural planting structure increases the content of soil organic carbon,and economic plants are of great significance to enhance the carbon sink function of the agricultural ecosystem in the loess gully area.展开更多
Dust aerosols profoundly influence the radiative balance of the earth–atmosphere system and hence the global and regional climates.In this study,using multi-source satellite and ground-level observations combined wit...Dust aerosols profoundly influence the radiative balance of the earth–atmosphere system and hence the global and regional climates.In this study,using multi-source satellite and ground-level observations combined with meteorological data,we investigated the three-dimensional evolution and transport characteristics of aerosols during a dust event that occurred in Xinjiang,China from 19 to 21 March 2019.Analysis of the meteorological data reveals that the dust air mass initially appeared in the northwest of Xinjiang and was subsequently transported to the Hami and Turpan areas due to the prevailing northwesterly winds,after which the direction of the airflow shifted due to topography,and the dust air masses were transported into southern Xinjiang.The air quality in the affected areas decreased rapidly,accompanied by a significant increase in aerosol optical depth (AOD),with the maximum value exceeding 3.5 in some areas.In addition,the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO) data reveal that the aerosol particles in the dust-affected areas were mainly dust aerosols,with small amounts of pollutant dust aerosols.A reduction in the attenuated backscatter coefficient (β532||) was found with increasing altitude,with the dust aerosol pollution mainly distributed in the lower troposphere.The size of dust particles in the lower troposphere was relatively small and irregular.The depolarization ratio (PDR) values at altitudes of 8–10 km were relatively lower than those recorded in the lower troposphere,whereas the color ratio (CR)values were higher,which may have been influenced by the sparse vegetation coverage and poor subsurface conditions in Xinjiang,and attributable to the fact that regular large particles of dust are more likely to be dispersed to altitudes between 8 and 10 km within a short period of time.As a consequence of the meteorological conditions and topography,the dusting process in Xinjiang persisted for a relatively long period.These findings will contribute to enhanced understanding of the vertical distribution of aerosols in Northwest China.展开更多
Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO...Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO,and nitrogen dioxide(NO_(2))were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAXDOAS)observations in Hefei,China.HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO_(2),which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes.Monthly means of HCHO concentrations were higher in summer,while enhanced amounts of NO_(2)were mainly observed in winter.CHOCHO exhibited a hump-like seasonal variation,with higher monthly-averaged values not only occurred in warm months(July-August)but also in cold months(November-December).Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO_(2),suggesting that HCHO is stronger link to photochemistry than CHOCHO.We further use the glyoxal to formaldehyde ratio(GFR)to investigate the VOC sources at different altitudes.The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km,and then rises rapidly as the altitude increases.The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes,while at higher altitudes is anthropogenic VOCs.Our findings provide a lot more insight into VOC sources at vertical direction,but more verification is recommended to be done in the future.展开更多
In order to study the regularity of the vertical distribution of droplet deposition on rice plants during pesticide spraying operated by a low-flying multi-rotor plant protection unmanned aviation vehicle(UAV),water-s...In order to study the regularity of the vertical distribution of droplet deposition on rice plants during pesticide spraying operated by a low-flying multi-rotor plant protection unmanned aviation vehicle(UAV),water-sensitive spray cards were placed on the leaves at the top,in the middle,and at the bottom of rice plants to acquire data on droplet deposition.In this study,a suspension containing tricylazole and hexaconazole was used in the spraying.The water-sensitive spray cards were analyzed by the droplet deposition processing software iDAS to obtain the vertical distribution of the droplets sprayed by the plant protection UAV.The results showed that (1)significant variation was found in the coverage of the droplets in different vertical positions of the rice plants.Within the effective spray width,the best coverage of the droplets was found in the area just below the rotors,whereas the coverage of areas farther away from the rotors was poor.For the different vertical positions of the rice plants,the overall droplet coverage was 58.38%at the top,33.55%in the middle,and 11.34%at the bottom of the plants;(2)for all vertical positions,the average size of the droplets ranged between 110μm and 140μm,which was suitable for the control of plant diseases and insect pests.The highest droplet density was found at the top of the plants,and the distribution of the droplet density was similar in the middle and at the bottom of the rice plants;(3)the diffusion ratio at the top of the rice plants(0.84)was better than that in the middle(0.57)and at the bottom(0.37).The overall relative span could meet the requirements for the actual application.Except for the position in the middle of the plants,the relative span for the other positions of the plants was over 0.67,which is the standard value.This study demonstrated the distribution regularity of droplet deposition along with the vertical direction of rice plants during UAV-based spraying,which is of guiding significance for the use of UAVs in plant protection,the improvement of chemical utilization efficiency,and the reduction of pesticide and fertilizer pollution.展开更多
Aims Optimizing water and fertilizer management for crops requires an understanding of root distribution.Maize(Zea mays L.)is currently the most widely planted cereal crop in China,yet the vertical dis-tribution of ma...Aims Optimizing water and fertilizer management for crops requires an understanding of root distribution.Maize(Zea mays L.)is currently the most widely planted cereal crop in China,yet the vertical dis-tribution of maize roots across different regions remains unknown.The aims of this work were(i)to quantify the effects of climate and soil texture on the vertical distribution of maize roots,and(ii)to show the depth distribution of root biomass in China.Methods We used data of maize root biomass from 11 Chinese ecological stations with discontinuous observations from 2004 to 2014 to fit the regression coefficientβfor an asymptotic equation Y=1-βd,where d is the soil depth and Y is the proportion of root biomass from the surface to depth d.A statistical model was then developed to quantify the effects of climate and soil texture on the fittedβval-ues.Using the statistical model,we map the depth distribution of maize root biomass in China.Important Findings Maize root biomass in the 0-100 cm soil depth varied by an order of magnitude at different stations,from 64 to 268 g m−2.Maize planted in sandy soils and/or maize with high accumu-lated temperature for development had higher root biomass and deeper rooting systems.The fittedβvalues ranged from 0.785 to 0.977,which can be modeled by an integration of the accu-mulated temperature during the maize growing period and the soil clay and sand fractions(R2=0.66,n=50,P<0.001).Up to 82%of maize planting regions in China showed shallower rooting systems where more than 90%and 95%of the root bio-mass occurred in the top 20 and 30 cm soil layers,respectively.Deeper rooting systems occurred in some temperate arid and temperate semi-arid regions,with less than 80%of the root bio-mass in the top 20 cm soil.Our findings highlighted the vertical distribution of maize roots,and underlined the spatial variability in the vertical distribution of roots across China’s planting areas of maize.展开更多
Information on the vertical distribution of air pollutants is essential for understanding their spatiotemporal evolution underlying urban atmospheric environment. This paper presents the SO_(2) profiles based on groun...Information on the vertical distribution of air pollutants is essential for understanding their spatiotemporal evolution underlying urban atmospheric environment. This paper presents the SO_(2) profiles based on ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAX-DOAS) measurements from March 2018 to February 2019 in Hefei, East China. SO_(2) decrease rapidly with increasing heights in the warm season, while lifted layers were observed in the cold season, indicating accumulation or long-range transport of SO_(2) in different seasons might occur at different heights. The diurnal variations of SO_(2) were roughly consistent for all four seasons, exhibiting the minimum at noon and higher values in the morning and late afternoon. Lifted layers of SO_(2) were observed in the morning for fall and winter, implying the accumulation or transport of SO_(2) in the morning mainly occurred at the top of the boundary layer. The bivariate polar plots showed that weighted SO_(2) concentrations in the lower altitude were weakly dependent on wind, but in the middle and upper altitudes, higher weighted SO_(2) concentrations were observed under conditions of middlehigh wind speed. Concentration weighted trajectory(CWT) analysis suggested that potential sources of SO_(2) in spring and summer were local and transported mainly occurred in the lower altitude from southern and eastern areas;while in fall and winter, SO_(2) concentrations were deeply affected by long-range transport from northwestern and northern polluted regions in the middle and upper altitudes. Our findings provide new insight into the impacts of regional transport at different heights in the boundary layer on SO_(2) pollution.展开更多
A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary...A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary waves are produced by means of gravitational collapse at the layer thickness ratio of 0.2, and the internal periodic waves are produced with rocker-flap wave maker at the layer thickness ratio of 0.93. The wave parameters are obtained through dyeing photography. The vertical cylinders of the same size are arranged in different depths. The horizontal force on each cylinder is measured and the vertical distribution rules are researched. The internal wave heights are changed to study the impact of wave heights on the force. The results show that the horizontal force of concave type internal solitary wave on vertical cylinder in the upper-layer fluid has the same direction as the wave propagating, while it has an opposite direction in the lower-layer. The horizontal force is not evenly distributed in the lower fluid. And the force at different depths increases along with wave height. Internal solitary wave can produce an impact load on the entire pile. The horizontal force of internal periodic waves on the vertical cylinders is periodically changed at the frequency of waves. The direction of the force is opposite in the upper and lower layers, and the value is close. In the upper layer except the depth close to the interface, the force is evenly distributed; but it tends to decrease with the deeper depth in the lower layer. A periodic shear load can be produced on the entire pile by internal periodic waves, and it may cause fatigue damage to structures.展开更多
Vertical variability in the bio-optical properties of seawater in the northern South China Sea(NSCS)including inherent optical properties(IOPs)and chlorophyll a concentration(Chl)were studied on the basis of in situ d...Vertical variability in the bio-optical properties of seawater in the northern South China Sea(NSCS)including inherent optical properties(IOPs)and chlorophyll a concentration(Chl)were studied on the basis of in situ data collected in summer 2008 using an absorption/attenuation spectrophotometer.An empirical model was developed to estimate Chl profiles based on the absorption line height at long wavelengths,with a relative root mean square error of 37.03%.Bio-optical properties exhibited large horizontal and vertical spatial variability.As influenced by coastal upwelling and the Zhujiang River(Pearl River)discharge,both IOPs and Chl exhibited high values in the surface waters of the inner shelf,which tended to decrease with distance offshore.Subsurface maximum layers of IOPs and Chl were observed in the middle and outer shelf regions,along with significantly higher values of attenuation coefficients beneath this layer that rapidly increased towards the bottom.In the open ocean,both IOPs and Chl exhibited consistent variability,with the subsurface maximum layer typically located at34–84 m.Phytoplankton were found to be one of the major components in determining the vertical variability of bio-optical properties,with their vertical dynamics influenced by both physical forcing and light attenuation effects.The depth of the subsurface maximum layer was found to be closely related to the fluctuation of the oceanic thermocline and the depth of the euphotic zone,which also affected the total integrated biomass of the upper ocean.Typically high values of attenuation coefficients observed in the bottom waters of the continental shelf reflected the transport of particulate matter over the bottom boundary layer.Our results reveal large spatial differences in bio-optical profiles in response to complex marine ecodynamics in the NSCS.From the perspective of marine research,high-resolution optical measurements are clearly advantageous over conventional bottle sampling.展开更多
A probability density function of surface elevation is obtained through improvement of the method introduced byCieslikiewicz who employed the maximum entropy principle to investigate the surface elevation distribution...A probability density function of surface elevation is obtained through improvement of the method introduced byCieslikiewicz who employed the maximum entropy principle to investigate the surface elevation distribution. The densityfunction can be easily extended to higher order according to demand and is non-negative everywhere, satisfying the basicbehavior of the probability. Moreover because the distribution is derived without any assumption about sea waves, it isfound from comparison with several accepted distributions that the new form of distribution can be applied in a widerrange of wave conditions. In addition, the density function can be used to fit some observed distributions of surface verti-cal acceleration although something remains unsolved.展开更多
Velocity vertical profiles in the bottom boundary layer are important to understand the oceanic circulation.The logarithmic vertical profile,u=A ln z+B,is the universal profile for the horizontal velocity in the bound...Velocity vertical profiles in the bottom boundary layer are important to understand the oceanic circulation.The logarithmic vertical profile,u=A ln z+B,is the universal profile for the horizontal velocity in the boundary layer,in which two coefficients(A and B)need to be determined.The two coefficients are the functions of the friction velocity(u_(*))and the roughness length(z_(0)),and they are calculated using u_(*)and z_(0).However,the measurement of u_(*)and z_(0) is a challenge.In the present study,an approach is developed to estimate the two coefficients(A and B)by using a series of fl ume laboratory experiments with fl at boundary and regularly distributed cylinders as the rough boundaries.An acoustic doppler velocimeter(ADV)is used to measure the velocity vertical profiles of the steady flow.Using the measured velocity data,the regressed logarithmic profiles are obtained.Based on the series of the A and B values,the mathematical formula for A and B are statistically established as the function of the cylinder height,inflow velocity,and the water depth,which avoids the measurement of the friction velocity and the roughness length.展开更多
Pollutants release is highly consistent with suspended sediment concentration(SSC) in water column, especially during re-suspension and transport events. The present research focuses on pollutant dynamic release from ...Pollutants release is highly consistent with suspended sediment concentration(SSC) in water column, especially during re-suspension and transport events. The present research focuses on pollutant dynamic release from re-suspended sediment, especially the vertical distribution relationship between them. The sediment erosion experiments on a series of uniform flow are conducted in a circulate flume. Reactive tracer(phosphorus)is used as the contaminant in fine-grained sediments to identify the release characteristic length and time. Experimental results show that the flow condition near-bed depends on the sediment surface roughness. The region with high turbulent intensities corresponds to a high concentration sediment layer. In addition, the SSC decreases with the distance,water depth, and particle grain size. The sediment in a smaller grain size takes much more time to reach equilibrium concentration. Total phosphorus(TP) concentration changes along the water depth as SSC in the initial re-suspension stage, appearing in two obvious concentration regimes: the upper low-concentration layer and the high-concentration near-bottom layer. This layered phenomenon remains for about 3 hours until SSC distribution tends to be uniform. Longitudinal desorption plays an important role in long-way transport to reduce the amount of suspended sediment in water column.展开更多
It is very important to understand the ecological and socio-economic factors in population distribution and their changes over time for the compilation of regional development planning and the guidance of rational pop...It is very important to understand the ecological and socio-economic factors in population distribution and their changes over time for the compilation of regional development planning and the guidance of rational population flow.Using surface-based population data for China from 1990 to 2015,the national distribution and dynamics of the human population by elevation are quantified based on 1-km cell-size gridded distribution datasets and 1-km cell-size DEM(digital elevation model).A geographical detector model is used to quantitatively analyze the dominant role of natural geographical factors,such as topography and climate,on the spatial distribution of population.Results show that:1)the population size and density decrease rapidly with elevation below 1000 m above the sea level,and the gap in population density between low-altitude areas and high-altitude areas increases with time because of the continuous growth of population density in low-altitude areas;2)the distribution of the population can be divided into five steps according to integrated population density(IPD),in proportions of 43∶35∶21∶1∶0,and that these proportions have remained stable over the last 25 yr;3)the basic pattern of population spatial distribution is determined by natural geographical environment factors,such as topography,climate,geomorphology,and their interactions;and 4)the development of society and the economy are the driving forces for the dynamic change in the population distribution during the study period,with the distribution pattern and dynamics of population by altitude in China providing a comprehensive reflection of various geographical elements on different spatial scales.展开更多
Ciliates are important components in planktonic food webs,but our understanding of their community structures in different oceanic water masses is limited.We report pelagic ciliate community characteristics in three s...Ciliates are important components in planktonic food webs,but our understanding of their community structures in different oceanic water masses is limited.We report pelagic ciliate community characteristics in three seas:the tropical West Pacific,the Bering Sea and the Arctic Ocean.Planktonic ciliate abundance had"bimodal-peak","surface-peak"and"DCM(deep chlorophyll a maximum layer)-peak"vertical distribution patterns in the tropical West Pacific,the Bering Sea and the Arctic Ocean,respectively.The abundance proportion of tintinnid to total ciliate in the Bering Sea(42.6%)was higher than both the tropical West Pacific(7.8%)and the Arctic Ocean(2.0%).The abundance proportion of small aloricate ciliates(10–20μm size-fraction)in the tropical West Pacific was highest in these three seas.The Arctic Ocean had higher abundance proportion of tintinnids in larger LOD(lorica oral diameter)size-class.Proportion of redundant species increased from the Arctic Ocean to the tropical West Pacific.Our result provided useful data to further understand ecology roles of planktonic ciliates in different marine habitats.展开更多
Trait structure is increasingly used in plankton ecology to understand diversity and biogeography.However,our knowledge of micro zooplankton(e.g.planktonic ciliates)trait structure and its variation with hydrography i...Trait structure is increasingly used in plankton ecology to understand diversity and biogeography.However,our knowledge of micro zooplankton(e.g.planktonic ciliates)trait structure and its variation with hydrography is limited.In this study,we analyzed planktonic ciliate trait structure in waters with different hydrography and deep Chlorophyll a maximum(DCM)layers over three seamounts:Yap,Mariana,and Caroline seamounts.Mariana seamount had a lower surface temperature than the Yap and Caroline seamounts.DCM layers over Mariana and Caroline seamounts were deeper than Yap seamount.There was a weak upwelling in upper 50 m around top of Mariana seamount.The ciliate distribution showed bimodal pattern(high abundance appeared in the surface and DCM layers)over three seamounts.At surface layer,the large size-fraction(>30μm)abundance proportion to aloricate ciliate over Yap seamount(44.4%)was higher than Mariana(32.8%)and Caroline(36.1%)seamounts.For tintinnid abundance proportion to total ciliate,Mariana(12.0%)and Caroline(11.5%)seamounts at about 100-m depth were higher than that of Yap seamount(6.4%).Vertically,tintinnid could be divided into 4 groups over the three seamounts.At30-m depth,group I(species occurring from surface to 100 m only)was dominant component over Yap and Caroline seamounts,while group IV(species occurring at every depth)changed into dominant component over Mariana seamount,the weak upwelling might be the reason.Salpingella faurei was the top dominant species,which corresponded to deeper DCM layers over Mariana and Caroline seamounts.Our results showed that the upwelling and the deeper DCM could influence the planktonic ciliate trait structure.展开更多
Convective/large-scale(C/L)precipitation partitions are crucial for achieving realistic rainfall modeling and are classified in 16 phase 6 of the Coupled Model Intercomparison Project(CMIP6)atmospheric models.Only 4 m...Convective/large-scale(C/L)precipitation partitions are crucial for achieving realistic rainfall modeling and are classified in 16 phase 6 of the Coupled Model Intercomparison Project(CMIP6)atmospheric models.Only 4 models capture the feature that convective rainfall significantly exceeds the large-scale rainfall component in the tropics while the other 12 models show 50%–100%large-scale rainfall component in heavy rainfall.Increased horizontal resolution generally increases the convective rainfall percentage,but not in all models.The former 4 models can realistically reproduce two peaks of moisture vertical distribution,respectively located in the upper and the lower troposphere.In contrast,the latter 12 models correspond to three types of moisture vertical profile biases:(1)whole mid-to-lower tropospheric wet biases(60%–80%large-scale rainfall);(2)mid-tropospheric wet peak(50%convective/large-scale rainfall);and(3)lower-tropospheric wet peak(90%–100%large-scale rainfall).And the associated vertical distribution of unique clouds potentially causes different climate feedback,suggesting accurate C/L rainfall components are necessary to reliable climate projection.展开更多
The Tlemcen region is located in north-western Algeria and is characterized by a semi-arid bioclimate. An approach to the diversity of the malacofauna associated with Salvia officinalis was carried out in three statio...The Tlemcen region is located in north-western Algeria and is characterized by a semi-arid bioclimate. An approach to the diversity of the malacofauna associated with Salvia officinalis was carried out in three stations belonging to this area from February to June 2015. The specific richness of the Gastropods is 9 divided into three families: Milacidae, Helicidae and Subulinidae. The second includes two subfamilies including that of Helicinae and that of Helicellinae. Two species are constant, 01 is incidental and the 06 others are very accidental. The relative importance of snails fluctuates according to the stations and according to the months and the seasons. In winter, in the first station the malacological richness is equal to 6. In February, the specific richness is relatively important in the 2nd station with a value equal to 7. Milax nigricans (Milacidae) has a frequency of 10% in station 1 and has a density of 0.1 in this same station. It is absent in the other two stations. Euparypha pisana has a frequency of 60% in station 3 and an abundance of 0.57 in this same station.展开更多
基金The authors wish to thank the Ecosystem Approach to the management of fisheries and the marine environment in the West African Waters(AWA)project.They also acknowledge support from the international joint laboratory ECLAIRS.The Laboratoire de Météorologie Dynamique(LMD)and the Global Challenges Research Fund(GCRF)African Science for Weather Information and Techniques(SWIFT)Programme.NASA,CNES,and ICARE are acknowledged for providing access to CALIOP and Sun photometer AERONET data.
文摘Saharan dust represents more than 50%of the total desert dust emitted around the globe and its radiative effect significantly affects the atmospheric circulation at a continental scale.Previous studies on dust vertical distribution and the Saharan Air Layer(SAL)showed some shortcomings that could be attributed to imperfect representation of the effects of deep convection and scavenging.The authors investigate here the role of deep convective transport and scavenging on the vertical distribution of mineral dust over Western Africa.Using multi-year(2006-2010)simulations performed with the variable-resolution(zoomed)version of the LMDZ climate model.Simulations are compared with aerosol amounts recorded by the Aerosol Robotic Network(AERONET)and with vertical profiles of the Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP)measurements.LMDZ allows a thorough examination of the respective roles of deep convective transport,convective and stratiform scavenging,boundary layer transport,and advection processes on the vertical mineral dust distribution over Western Africa.The comparison of simulated dust Aerosol Optical Depth(AOD)and distribution with measurements suggest that scavenging in deep convection and subsequent re-evaporation of dusty rainfall in the lower troposphere are critical processes for explaining the vertical distribution of desert dust.These processes play a key role in maintaining a well-defined dust layer with a sharp transition at the top of the SAL and in establishing the seasonal cycle of dust distribution.This vertical distribution is further reshaped offshore in the Inter-Tropical Convergence Zone(ITCZ)over the Atlantic Ocean by marine boundary layer turbulent and convective transport and wet deposition at the surface.
基金supported by the National Natural Science Foundation of China (No.41606138)the Special Funds of Basic Research of Central Public Welfare Institute (Nos.2019T09, 2016Z01-02)+1 种基金the National Key Research and Development Project of China (No.2019YFD 0901405)the Fund of Key Laboratory of Open-Sea Fishery Development, Ministry of Agriculture, P.R.China (No.LOF2018-01)。
文摘Understanding the potential vertical distribution of bigeye tuna(Thunnus obesus) is necessary to understand the catch rate fluctuations and the stock assessment of bigeye tuna. To characterize the potential vertical distribution of this fish while foraging and determine the influences of the distribution on longline efficiency in the tropical Atlantic Ocean, the catch per unit effort(CPUE) data were compiled from the International Commission for the Conservation of Atlantic Tunas and the Argo buoy data were downloaded from the Argo data center. The raw Argo buoy data were processed by data mining methods. The CPUE was standardized by support vector machine before analysis. We assumed the depths with the upper and lower limits of the optimum water temperatures of 15℃ and 9℃ as the preferred swimming depth, while the lower limit of the temperature(12℃) associated with the highest hooking rate as the preferred foraging depth(D12) of bigeye tuna during the daytime in the Atlantic Ocean. The preferred swimming depth and foraging depth range in the daytime were assessed by plotting the isobath based on Argo buoy data. The preferred swimming depth and vertical structure of the water column were identified to investigate the spatial effects on the CPUE by using a generalized additive model(GAM). The empirical cumulative distribution function was used to assess the relationship between the spatial distribution of CPUE and the depth of 12℃ isolines and thermocline. The results indicate that 1) the preferred swimming depth of bigeye tuna in the tropical Atlantic is from 100 m to 400 m and displays spatial variation;2) the preferred foraging depth of bigeye tuna is between 190 and 300 m and below the thermocline;3) the number of CPUEs peaks at a relative depth of 30 –50 m(difference between the 12℃ isolines and the lower boundary of the thermocline);and 4) most CPUEs are within the lower depth boundary of the thermocline levels(LDBT) which is from 160 m to 230 m. GAM analysis indicates that the general relationship between the nominal CPUE and LDBT is characterized by a dome shape and peaks at approximately 190 m. The oceanographic features influence the habitat of tropical pelagic fish and fisheries. Argo buoy data can be an important tool to describe the habitat of oceanic fish. Our results provide new insights into how oceanographic features influence the habitat of tropical pelagic fish and fisheries and how fisheries exploit these fish using a new tool(Argo profile data).
基金Supported by the China Ocean Mineral Resources R&D Association(Nos.DY135-B2-11,DY135-E2-4)the National Natural Science Foundation of China(No.42076165)+2 种基金the Natural Science Foundation of Shandong Province(No.ZR2018MD017)the National Key Research and Development Program(No.2016YFC1402301)the Fundamental Research Funds for the Central Universities(No.201822009)。
文摘Although the microbial diversity of the Indian Ocean has been extensively investigated,little is known about the community composition of microbes in the Southern Indian Ocean.In the present study,we divided 60 water column samples on the Ninety-East Ridge(NER)into fi ve water masses according to the temperature-salinity curves.We presented,for the fi rst time,a full description of the microbial biodiversity on NER through high-throughput amplicon sequencing approach,including bacteria,archaea,and fungi.We found that bacteria exhibited higher richness and diversity than archaea and fungi across the water masses on NER.More importantly,each water mass on NER featured distinct prokaryotic microbial communities,as indicated by the results of non-metric multidimensional scaling.In contrast,fungi were eurybathic across the water masses.Redundancy analysis results demonstrated that environmental factors might play a pivotal role in the formation and stability of prokaryotic communities in each water mass,especially that of archaea.In addition,indicator species might be used as fi ngerprints to identify corresponding water masses on NER.These results provide new insights into the vertical distribution,structure,and diversity of microorganisms on NER from the perspective of water mass.
基金supported by the National Basic Research Program of China (Grant No.2006CB403702)the National Natural Science Foundation of China (Grant No. 40475014)
文摘Based on the Stratospheric Aerosol and Gas Experiment (SAGE) II and the Halogen Occultation Ex-periment (HALOE) ozone profiles and the Total Ozone Mapping Spectrometer (TOMS) total ozone data sets,the characteristics and variations of the vertical distribution of stratospheric ozone covering the latitude bands of 50oN±5oN,40oN±5oN,30oN±5oN,and 20oN±5oN and the longitude range of 75-135oE are investigated.The results indicate that the ozone distribution pattern over China not only has general behaviors,but also has particular char-acteristics.In view of the situation that ozone distribu-tions have substantial deviation from zonal symmetry in northern China,the differences of the vertical ozone dis-tribution between the east and the west part of northern China are studied.The results indicate that during winter,spring,and autumn,in the latitude bands of 50oN±5oN,40oN±5oN,ozone concentrations in the eastern part (105 -135oE) are obviously higher than those of the west (75-105oE) at the altitudes of ozone density maximum and below;during summer,in the latitude band of 50oN±5oN,the east-west ozone profile difference is small,but in the latitude band of 40oN±5oN,the east-west total ozone difference becomes as large as 14.0 DU,and the east-west ozone profile difference mainly exists in the lowermost stratosphere and troposphere.
基金Supported by National Science Foundation of China (32271848)。
文摘Three economic plants from the loess gully areas in China to explore the changing vertical distribution characteristics of soil organic carbon.The results showed that:(1) with the increase of depth,the average SOC content of economic plants decreased from 13.98 to 1.39 g/kg on the 0-100 cm soil profile,in the form of a power function;(2) the constructed depth spatial distribution models for different plants could help accurately assess the spatial distribution pattern of soil organic carbon;(3) compared with traditional agricultural planting,the carbon sink function for walnut and grape at a soil depth of 100 cm increased by 92.8±8.98 t/hm^(2) and 45.7±7.7 t/hm^(2),respectively.The adjustment of agricultural planting structure increases the content of soil organic carbon,and economic plants are of great significance to enhance the carbon sink function of the agricultural ecosystem in the loess gully area.
基金Supported by the National Natural Science Foundation of China(41771470).
文摘Dust aerosols profoundly influence the radiative balance of the earth–atmosphere system and hence the global and regional climates.In this study,using multi-source satellite and ground-level observations combined with meteorological data,we investigated the three-dimensional evolution and transport characteristics of aerosols during a dust event that occurred in Xinjiang,China from 19 to 21 March 2019.Analysis of the meteorological data reveals that the dust air mass initially appeared in the northwest of Xinjiang and was subsequently transported to the Hami and Turpan areas due to the prevailing northwesterly winds,after which the direction of the airflow shifted due to topography,and the dust air masses were transported into southern Xinjiang.The air quality in the affected areas decreased rapidly,accompanied by a significant increase in aerosol optical depth (AOD),with the maximum value exceeding 3.5 in some areas.In addition,the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO) data reveal that the aerosol particles in the dust-affected areas were mainly dust aerosols,with small amounts of pollutant dust aerosols.A reduction in the attenuated backscatter coefficient (β532||) was found with increasing altitude,with the dust aerosol pollution mainly distributed in the lower troposphere.The size of dust particles in the lower troposphere was relatively small and irregular.The depolarization ratio (PDR) values at altitudes of 8–10 km were relatively lower than those recorded in the lower troposphere,whereas the color ratio (CR)values were higher,which may have been influenced by the sparse vegetation coverage and poor subsurface conditions in Xinjiang,and attributable to the fact that regular large particles of dust are more likely to be dispersed to altitudes between 8 and 10 km within a short period of time.As a consequence of the meteorological conditions and topography,the dusting process in Xinjiang persisted for a relatively long period.These findings will contribute to enhanced understanding of the vertical distribution of aerosols in Northwest China.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Natural Science Foundation of China(Nos.51778596,41977184,and 41941011)+5 种基金the Key Research and Development Project of Anhui Province(202104i07020002)the Anhui Science and Technology Major Project(No.18030801111)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(05-Y30B01-9001-19/20-3)the Youth Innovation Promotion Association of CAS(2021443)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(CERAE202004)the Fundamental Research Funds for the Central Universities(No.JUSRP12042)。
文摘Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO,and nitrogen dioxide(NO_(2))were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAXDOAS)observations in Hefei,China.HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO_(2),which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes.Monthly means of HCHO concentrations were higher in summer,while enhanced amounts of NO_(2)were mainly observed in winter.CHOCHO exhibited a hump-like seasonal variation,with higher monthly-averaged values not only occurred in warm months(July-August)but also in cold months(November-December).Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO_(2),suggesting that HCHO is stronger link to photochemistry than CHOCHO.We further use the glyoxal to formaldehyde ratio(GFR)to investigate the VOC sources at different altitudes.The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km,and then rises rapidly as the altitude increases.The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes,while at higher altitudes is anthropogenic VOCs.Our findings provide a lot more insight into VOC sources at vertical direction,but more verification is recommended to be done in the future.
基金supported by the Key R&D Program of Liaoning Province(2020JH2/10200038)the National Key R&D Program of China(2016YFD0200700).
文摘In order to study the regularity of the vertical distribution of droplet deposition on rice plants during pesticide spraying operated by a low-flying multi-rotor plant protection unmanned aviation vehicle(UAV),water-sensitive spray cards were placed on the leaves at the top,in the middle,and at the bottom of rice plants to acquire data on droplet deposition.In this study,a suspension containing tricylazole and hexaconazole was used in the spraying.The water-sensitive spray cards were analyzed by the droplet deposition processing software iDAS to obtain the vertical distribution of the droplets sprayed by the plant protection UAV.The results showed that (1)significant variation was found in the coverage of the droplets in different vertical positions of the rice plants.Within the effective spray width,the best coverage of the droplets was found in the area just below the rotors,whereas the coverage of areas farther away from the rotors was poor.For the different vertical positions of the rice plants,the overall droplet coverage was 58.38%at the top,33.55%in the middle,and 11.34%at the bottom of the plants;(2)for all vertical positions,the average size of the droplets ranged between 110μm and 140μm,which was suitable for the control of plant diseases and insect pests.The highest droplet density was found at the top of the plants,and the distribution of the droplet density was similar in the middle and at the bottom of the rice plants;(3)the diffusion ratio at the top of the rice plants(0.84)was better than that in the middle(0.57)and at the bottom(0.37).The overall relative span could meet the requirements for the actual application.Except for the position in the middle of the plants,the relative span for the other positions of the plants was over 0.67,which is the standard value.This study demonstrated the distribution regularity of droplet deposition along with the vertical direction of rice plants during UAV-based spraying,which is of guiding significance for the use of UAVs in plant protection,the improvement of chemical utilization efficiency,and the reduction of pesticide and fertilizer pollution.
基金This work was jointly supported by the National Natural Science Foundation of China(Grant Nos.41530533 and 31370492).
文摘Aims Optimizing water and fertilizer management for crops requires an understanding of root distribution.Maize(Zea mays L.)is currently the most widely planted cereal crop in China,yet the vertical dis-tribution of maize roots across different regions remains unknown.The aims of this work were(i)to quantify the effects of climate and soil texture on the vertical distribution of maize roots,and(ii)to show the depth distribution of root biomass in China.Methods We used data of maize root biomass from 11 Chinese ecological stations with discontinuous observations from 2004 to 2014 to fit the regression coefficientβfor an asymptotic equation Y=1-βd,where d is the soil depth and Y is the proportion of root biomass from the surface to depth d.A statistical model was then developed to quantify the effects of climate and soil texture on the fittedβval-ues.Using the statistical model,we map the depth distribution of maize root biomass in China.Important Findings Maize root biomass in the 0-100 cm soil depth varied by an order of magnitude at different stations,from 64 to 268 g m−2.Maize planted in sandy soils and/or maize with high accumu-lated temperature for development had higher root biomass and deeper rooting systems.The fittedβvalues ranged from 0.785 to 0.977,which can be modeled by an integration of the accu-mulated temperature during the maize growing period and the soil clay and sand fractions(R2=0.66,n=50,P<0.001).Up to 82%of maize planting regions in China showed shallower rooting systems where more than 90%and 95%of the root bio-mass occurred in the top 20 and 30 cm soil layers,respectively.Deeper rooting systems occurred in some temperate arid and temperate semi-arid regions,with less than 80%of the root bio-mass in the top 20 cm soil.Our findings highlighted the vertical distribution of maize roots,and underlined the spatial variability in the vertical distribution of roots across China’s planting areas of maize.
基金jointly supported by the National Key Research and Development Program of China(Nos.2017YFC0210002,2018YFC0213104 and 2016YFC0203302)National Natural Science Foundation of China(Nos.41722501,51778596 and 41977184)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(Nos.DQGG0102 and DQGG0205)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(05-Y30B01-9001-19/20-3)the Fundamental Research Funds for the Central Universities(No.JUSRP12042)。
文摘Information on the vertical distribution of air pollutants is essential for understanding their spatiotemporal evolution underlying urban atmospheric environment. This paper presents the SO_(2) profiles based on ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAX-DOAS) measurements from March 2018 to February 2019 in Hefei, East China. SO_(2) decrease rapidly with increasing heights in the warm season, while lifted layers were observed in the cold season, indicating accumulation or long-range transport of SO_(2) in different seasons might occur at different heights. The diurnal variations of SO_(2) were roughly consistent for all four seasons, exhibiting the minimum at noon and higher values in the morning and late afternoon. Lifted layers of SO_(2) were observed in the morning for fall and winter, implying the accumulation or transport of SO_(2) in the morning mainly occurred at the top of the boundary layer. The bivariate polar plots showed that weighted SO_(2) concentrations in the lower altitude were weakly dependent on wind, but in the middle and upper altitudes, higher weighted SO_(2) concentrations were observed under conditions of middlehigh wind speed. Concentration weighted trajectory(CWT) analysis suggested that potential sources of SO_(2) in spring and summer were local and transported mainly occurred in the lower altitude from southern and eastern areas;while in fall and winter, SO_(2) concentrations were deeply affected by long-range transport from northwestern and northern polluted regions in the middle and upper altitudes. Our findings provide new insight into the impacts of regional transport at different heights in the boundary layer on SO_(2) pollution.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51279187 and 41174157)the Fundamental Research Funds for the Central Universities(Grant No.201262005)the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province(Grant No.BS2013HZ014)
文摘A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary waves are produced by means of gravitational collapse at the layer thickness ratio of 0.2, and the internal periodic waves are produced with rocker-flap wave maker at the layer thickness ratio of 0.93. The wave parameters are obtained through dyeing photography. The vertical cylinders of the same size are arranged in different depths. The horizontal force on each cylinder is measured and the vertical distribution rules are researched. The internal wave heights are changed to study the impact of wave heights on the force. The results show that the horizontal force of concave type internal solitary wave on vertical cylinder in the upper-layer fluid has the same direction as the wave propagating, while it has an opposite direction in the lower-layer. The horizontal force is not evenly distributed in the lower fluid. And the force at different depths increases along with wave height. Internal solitary wave can produce an impact load on the entire pile. The horizontal force of internal periodic waves on the vertical cylinders is periodically changed at the frequency of waves. The direction of the force is opposite in the upper and lower layers, and the value is close. In the upper layer except the depth close to the interface, the force is evenly distributed; but it tends to decrease with the deeper depth in the lower layer. A periodic shear load can be produced on the entire pile by internal periodic waves, and it may cause fatigue damage to structures.
基金The National Natural Science Foundation of China under contract Nos 41776045 and 41576030the Fundamental Research Funds for the Central Universities under contract No.2017B06714+1 种基金the Open Project Program of the State Key Laboratory of Tropical Oceanography under contract No.LTOZZ1602the Science and Technology Program of Guangzhou,China under contract No.201607020041
文摘Vertical variability in the bio-optical properties of seawater in the northern South China Sea(NSCS)including inherent optical properties(IOPs)and chlorophyll a concentration(Chl)were studied on the basis of in situ data collected in summer 2008 using an absorption/attenuation spectrophotometer.An empirical model was developed to estimate Chl profiles based on the absorption line height at long wavelengths,with a relative root mean square error of 37.03%.Bio-optical properties exhibited large horizontal and vertical spatial variability.As influenced by coastal upwelling and the Zhujiang River(Pearl River)discharge,both IOPs and Chl exhibited high values in the surface waters of the inner shelf,which tended to decrease with distance offshore.Subsurface maximum layers of IOPs and Chl were observed in the middle and outer shelf regions,along with significantly higher values of attenuation coefficients beneath this layer that rapidly increased towards the bottom.In the open ocean,both IOPs and Chl exhibited consistent variability,with the subsurface maximum layer typically located at34–84 m.Phytoplankton were found to be one of the major components in determining the vertical variability of bio-optical properties,with their vertical dynamics influenced by both physical forcing and light attenuation effects.The depth of the subsurface maximum layer was found to be closely related to the fluctuation of the oceanic thermocline and the depth of the euphotic zone,which also affected the total integrated biomass of the upper ocean.Typically high values of attenuation coefficients observed in the bottom waters of the continental shelf reflected the transport of particulate matter over the bottom boundary layer.Our results reveal large spatial differences in bio-optical profiles in response to complex marine ecodynamics in the NSCS.From the perspective of marine research,high-resolution optical measurements are clearly advantageous over conventional bottle sampling.
基金This project was financially supported by the National Natural Science Foundation of China(Grant No.49876012,49976003)
文摘A probability density function of surface elevation is obtained through improvement of the method introduced byCieslikiewicz who employed the maximum entropy principle to investigate the surface elevation distribution. The densityfunction can be easily extended to higher order according to demand and is non-negative everywhere, satisfying the basicbehavior of the probability. Moreover because the distribution is derived without any assumption about sea waves, it isfound from comparison with several accepted distributions that the new form of distribution can be applied in a widerrange of wave conditions. In addition, the density function can be used to fit some observed distributions of surface verti-cal acceleration although something remains unsolved.
基金Supported by the National Key Research and Development Program of China(Nos.2017YFA0604100,2016YFA0601803,2016YFC1401407)the National Natural Science Foundation of China(Nos.41490643,41706008)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110840)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.311020004)the Key Program of Marine Economy Development(Six Marine Industries)Special Foundation of Department of Natural Resources of Guangdong Province(No.GDNRC[2020]049)。
文摘Velocity vertical profiles in the bottom boundary layer are important to understand the oceanic circulation.The logarithmic vertical profile,u=A ln z+B,is the universal profile for the horizontal velocity in the boundary layer,in which two coefficients(A and B)need to be determined.The two coefficients are the functions of the friction velocity(u_(*))and the roughness length(z_(0)),and they are calculated using u_(*)and z_(0).However,the measurement of u_(*)and z_(0) is a challenge.In the present study,an approach is developed to estimate the two coefficients(A and B)by using a series of fl ume laboratory experiments with fl at boundary and regularly distributed cylinders as the rough boundaries.An acoustic doppler velocimeter(ADV)is used to measure the velocity vertical profiles of the steady flow.Using the measured velocity data,the regressed logarithmic profiles are obtained.Based on the series of the A and B values,the mathematical formula for A and B are statistically established as the function of the cylinder height,inflow velocity,and the water depth,which avoids the measurement of the friction velocity and the roughness length.
基金Project supported by the National Natural Science Foundation of China(No.10972134)the National Key Program of National Natural Science Foundation of China(No.11032007)the Shanghai Program for Innovative Research Team in Universities
文摘Pollutants release is highly consistent with suspended sediment concentration(SSC) in water column, especially during re-suspension and transport events. The present research focuses on pollutant dynamic release from re-suspended sediment, especially the vertical distribution relationship between them. The sediment erosion experiments on a series of uniform flow are conducted in a circulate flume. Reactive tracer(phosphorus)is used as the contaminant in fine-grained sediments to identify the release characteristic length and time. Experimental results show that the flow condition near-bed depends on the sediment surface roughness. The region with high turbulent intensities corresponds to a high concentration sediment layer. In addition, the SSC decreases with the distance,water depth, and particle grain size. The sediment in a smaller grain size takes much more time to reach equilibrium concentration. Total phosphorus(TP) concentration changes along the water depth as SSC in the initial re-suspension stage, appearing in two obvious concentration regimes: the upper low-concentration layer and the high-concentration near-bottom layer. This layered phenomenon remains for about 3 hours until SSC distribution tends to be uniform. Longitudinal desorption plays an important role in long-way transport to reduce the amount of suspended sediment in water column.
基金Under the auspices of National Key R&D Projects(No.2017YFC0504705)the Western and Frontier Youth Project of Ministry of Education Humanities and Social Sciences(No.12XJC840001)。
文摘It is very important to understand the ecological and socio-economic factors in population distribution and their changes over time for the compilation of regional development planning and the guidance of rational population flow.Using surface-based population data for China from 1990 to 2015,the national distribution and dynamics of the human population by elevation are quantified based on 1-km cell-size gridded distribution datasets and 1-km cell-size DEM(digital elevation model).A geographical detector model is used to quantitatively analyze the dominant role of natural geographical factors,such as topography and climate,on the spatial distribution of population.Results show that:1)the population size and density decrease rapidly with elevation below 1000 m above the sea level,and the gap in population density between low-altitude areas and high-altitude areas increases with time because of the continuous growth of population density in low-altitude areas;2)the distribution of the population can be divided into five steps according to integrated population density(IPD),in proportions of 43∶35∶21∶1∶0,and that these proportions have remained stable over the last 25 yr;3)the basic pattern of population spatial distribution is determined by natural geographical environment factors,such as topography,climate,geomorphology,and their interactions;and 4)the development of society and the economy are the driving forces for the dynamic change in the population distribution during the study period,with the distribution pattern and dynamics of population by altitude in China providing a comprehensive reflection of various geographical elements on different spatial scales.
基金The National Natural Science Foundation of China under contract No.41706192the Science&Technology Basic Resources Investigation Program of China under contract No.2017FY100803+3 种基金the National Natural Science Foundation of ChinaShandong Joint Fund for Marine Science Research Centers under contract No.U1606404the CNRS-NSFC Joint Research Projects Program under contract No.NSFC 41711530149the 2017–2019 Sino-French Cai Yuanpei Programmethe National Natural Science Foundation of China under contract No.41706217
文摘Ciliates are important components in planktonic food webs,but our understanding of their community structures in different oceanic water masses is limited.We report pelagic ciliate community characteristics in three seas:the tropical West Pacific,the Bering Sea and the Arctic Ocean.Planktonic ciliate abundance had"bimodal-peak","surface-peak"and"DCM(deep chlorophyll a maximum layer)-peak"vertical distribution patterns in the tropical West Pacific,the Bering Sea and the Arctic Ocean,respectively.The abundance proportion of tintinnid to total ciliate in the Bering Sea(42.6%)was higher than both the tropical West Pacific(7.8%)and the Arctic Ocean(2.0%).The abundance proportion of small aloricate ciliates(10–20μm size-fraction)in the tropical West Pacific was highest in these three seas.The Arctic Ocean had higher abundance proportion of tintinnids in larger LOD(lorica oral diameter)size-class.Proportion of redundant species increased from the Arctic Ocean to the tropical West Pacific.Our result provided useful data to further understand ecology roles of planktonic ciliates in different marine habitats.
基金the Science&Technology Basic Resources Investigation Program of China(No.2017FY100803)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42000000)+5 种基金the China Postdoctoral Science Foundation(No.2020M672149)the National Key Research and Development Program of China(No.2017YFA0603204)the CNRS-NSFC Joint Research Projects Program(No.NSFC 41711530149)the 2017-2019 Sino-French Cai Yuanpei Programthe International Cooperation Project-Dynamics and Function of Marine Microorganisms(No.ICP-DYF2M):Insight from Physics and Remote Sensing。
文摘Trait structure is increasingly used in plankton ecology to understand diversity and biogeography.However,our knowledge of micro zooplankton(e.g.planktonic ciliates)trait structure and its variation with hydrography is limited.In this study,we analyzed planktonic ciliate trait structure in waters with different hydrography and deep Chlorophyll a maximum(DCM)layers over three seamounts:Yap,Mariana,and Caroline seamounts.Mariana seamount had a lower surface temperature than the Yap and Caroline seamounts.DCM layers over Mariana and Caroline seamounts were deeper than Yap seamount.There was a weak upwelling in upper 50 m around top of Mariana seamount.The ciliate distribution showed bimodal pattern(high abundance appeared in the surface and DCM layers)over three seamounts.At surface layer,the large size-fraction(>30μm)abundance proportion to aloricate ciliate over Yap seamount(44.4%)was higher than Mariana(32.8%)and Caroline(36.1%)seamounts.For tintinnid abundance proportion to total ciliate,Mariana(12.0%)and Caroline(11.5%)seamounts at about 100-m depth were higher than that of Yap seamount(6.4%).Vertically,tintinnid could be divided into 4 groups over the three seamounts.At30-m depth,group I(species occurring from surface to 100 m only)was dominant component over Yap and Caroline seamounts,while group IV(species occurring at every depth)changed into dominant component over Mariana seamount,the weak upwelling might be the reason.Salpingella faurei was the top dominant species,which corresponded to deeper DCM layers over Mariana and Caroline seamounts.Our results showed that the upwelling and the deeper DCM could influence the planktonic ciliate trait structure.
基金funding from the National Natural Science Foundation of China(Grant 42022034,91737306,41675100)National Key Research and development Program of China(Grant No.2017YFA0604004)。
文摘Convective/large-scale(C/L)precipitation partitions are crucial for achieving realistic rainfall modeling and are classified in 16 phase 6 of the Coupled Model Intercomparison Project(CMIP6)atmospheric models.Only 4 models capture the feature that convective rainfall significantly exceeds the large-scale rainfall component in the tropics while the other 12 models show 50%–100%large-scale rainfall component in heavy rainfall.Increased horizontal resolution generally increases the convective rainfall percentage,but not in all models.The former 4 models can realistically reproduce two peaks of moisture vertical distribution,respectively located in the upper and the lower troposphere.In contrast,the latter 12 models correspond to three types of moisture vertical profile biases:(1)whole mid-to-lower tropospheric wet biases(60%–80%large-scale rainfall);(2)mid-tropospheric wet peak(50%convective/large-scale rainfall);and(3)lower-tropospheric wet peak(90%–100%large-scale rainfall).And the associated vertical distribution of unique clouds potentially causes different climate feedback,suggesting accurate C/L rainfall components are necessary to reliable climate projection.
文摘The Tlemcen region is located in north-western Algeria and is characterized by a semi-arid bioclimate. An approach to the diversity of the malacofauna associated with Salvia officinalis was carried out in three stations belonging to this area from February to June 2015. The specific richness of the Gastropods is 9 divided into three families: Milacidae, Helicidae and Subulinidae. The second includes two subfamilies including that of Helicinae and that of Helicellinae. Two species are constant, 01 is incidental and the 06 others are very accidental. The relative importance of snails fluctuates according to the stations and according to the months and the seasons. In winter, in the first station the malacological richness is equal to 6. In February, the specific richness is relatively important in the 2nd station with a value equal to 7. Milax nigricans (Milacidae) has a frequency of 10% in station 1 and has a density of 0.1 in this same station. It is absent in the other two stations. Euparypha pisana has a frequency of 60% in station 3 and an abundance of 0.57 in this same station.
