Crushed rock layers(CRLs),ventilation ducts(VDs)and thermosyphons are air-cooling structures(ACSs)widely used for maintaining the long-term stability of engineered infrastructures in permafrost environments.These ACSs...Crushed rock layers(CRLs),ventilation ducts(VDs)and thermosyphons are air-cooling structures(ACSs)widely used for maintaining the long-term stability of engineered infrastructures in permafrost environments.These ACSs can effectively cool and maintain the permafrost subgrade’s frozen state under climate warming by facilitating heat exchange with ambient air in cold seasons.As convection is a crucial working mechanism of these ACSs,it is imperative to understand the near-surface wind flow(NSWF)across a constructed infrastructure,such as an embankment.This article describes a yearlong field observation of the NSWF across an experimental expressway embankment,the first of its kind on the Qinghai–Tibet Plateau(QTP).The wind speed and direction along a transect perpendicular to the embankment on both the windward and leeward sides and at four different heights above the ground surface were collected and analyzed.The results showed that the embankment has a considerable impact on the NSWF speed within a distance of up to ten times its height,and in the direction on the leeward side.A power law can well describe the speed profiles of NSWF across the embankment,with the power-law indices(PLIs)varying from 0.14 to 0.40.On an annual basis,the fitted NSWF PLI far away from the embankment was 0.19,which differs substantially from the values widely used in previous thermal performance evaluations of ACSs on the QTP.Finally,the significance of the NSWF to the thermal performance of the ACSs,particularly the CRLs and VDs,in linear transportation infrastructure is discussed.It is concluded that underestimating the PLI and neglecting wind direction variations may lead to unconservative designs of the ACSs.The results reported in this study can provide valuable guidance for infrastructure engineering on the QTP and other similar permafrost regions.展开更多
The source region of the Yellow River, accounting for over 38% of its total runoff, is a critical catchment area,primarily characterized by alpine grasslands. In 2005, the Maqu land surface processes observational sit...The source region of the Yellow River, accounting for over 38% of its total runoff, is a critical catchment area,primarily characterized by alpine grasslands. In 2005, the Maqu land surface processes observational site was established to monitor climate, land surface dynamics, and hydrological variability in this region. Over a 10-year period(2010–19), an extensive observational dataset was compiled, now available to the scientific community. This dataset includes comprehensive details on site characteristics, instrumentation, and data processing methods, covering meteorological and radiative fluxes, energy exchanges, soil moisture dynamics, and heat transfer properties. The dataset is particularly valuable for researchers studying land surface processes, land–atmosphere interactions, and climate modeling, and may also benefit ecological, hydrological, and water resource studies. The report ends with a discussion on perspectives and challenges of continued observational monitoring in this region, focusing on issues such as cryosphere influences, complex topography,and ecological changes like the encroachment of weeds and scrubland.展开更多
Aiming at node deployment in the monitoring area of the field observation instrument network in the cold and arid regions,we propose a virtual force algorithm based on Voronoi diagram(VFAVD),which adopts probabilistic...Aiming at node deployment in the monitoring area of the field observation instrument network in the cold and arid regions,we propose a virtual force algorithm based on Voronoi diagram(VFAVD),which adopts probabilistic sensing model that is more in line with the actual situation.First,the Voronoi diagram is constructed in the monitoring area to determine the Thiessen polygon of each node.Then,the virtual force on each node is calculated,and the node update its position according to the direction and size of the total force,so as to achieve the purpose of improving the network coverage rate.The simulation results show that the proposed algorithm can effectively improve the coverage rate of the network,and also has a good effect on the coverage uniformity.展开更多
Radio observations of some active regions (ARs) obtained with the Nobeyama radioheliograph at λ=1.76 cm are used for estimating the magnetic field strength in the upper chromosphere, based on thermal bremsstrahlung. ...Radio observations of some active regions (ARs) obtained with the Nobeyama radioheliograph at λ=1.76 cm are used for estimating the magnetic field strength in the upper chromosphere, based on thermal bremsstrahlung. The results are compared with the magnetic field strength in the photosphere from observations with the Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station of Beijing Astronomical Observatory. The difference in the magnetic field strength between the two layers seems reasonable. The solar radio maps of active regions obtained with the Nobeyama radioheliograph, both in total intensity (I-map) and in circular polarizations (V-map), are compared with the optical magnetograms obtained with the SMFT. The comparison between the radio map in circular polarization and the longitudinal photospheric magnetogram of a plage region suggests that the radio map in circular polarization is a kind of magnetogram of the upper chromosphere. The comparison of the radio map in total intensity with the photo-spheric vector magnetogram of an AR shows that the radio map in total intensity gives indications of magnetic loops in the corona, thus we have a method of defining the coronal magnetic structure from the radio I-maps at λ=1.76 cm. Analysing the I-maps, we identified three components: (a) a compact bright source; (b) a narrow elongated structure connecting two main magnetic islands of opposite polarities (observed in both the optical and radio magnetograms); (c) a wide, diffuse, weak component that corresponds to a wide structure in the solar active region which shows in most cases an S or a reversed S contour, which is probably due to the differential rotation of the Sun. The last two components suggest coronal loops on different spatial scales above the neutral line of the longitudinal photospheric magnetic field.展开更多
Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studi...Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.展开更多
The Macao Science Satellite-1(MSS-1)is the first space science satellite jointly developed on the Chinese mainland and in Macao region.It comprises two satellites,named MSS-1A and MSS-1B,and holds considerable importa...The Macao Science Satellite-1(MSS-1)is the first space science satellite jointly developed on the Chinese mainland and in Macao region.It comprises two satellites,named MSS-1A and MSS-1B,and holds considerable importance in China’s space exploration endeavors.Among these,MSS-1A is the world’s first high-precision scientific satellite dedicated to exploring the geomagnetic field and space environment at low latitudes.Equipped with two high-precision vector magnetometers and one scalar magnetometer,which are integrally installed on a highly stable nonmagnetic optical bench,the MSS-1A enables simultaneous high-precision measurements of both the Earth’s vector magnetic field and its scalar components.Its design integrates several state-of-the-art technologies,including arc-second-level thermal stability control,nonmagnetic thermal control for the optical bench,and ultra-high magnetic cleanliness control.These innovations effectively minimize magnetic interference originating from the satellite itself,thereby substantially improving the precision of geomagnetic field measurements and establishing a robust technical foundation for future magnetic survey satellite constellations.展开更多
Accurately estimating the wheat yield potential under climate changes is essential for assessing food production capacity. However, studies based on crop modeling and imperfect management experiment data frequently un...Accurately estimating the wheat yield potential under climate changes is essential for assessing food production capacity. However, studies based on crop modeling and imperfect management experiment data frequently underestimate the wheat yield potential. In this study, we evaluated wheat yield potential based on the CERES-Wheat model and a well-managed 10-year(2008–2017) field study in the North China Plain(NCP), and further identified the critical climate and management yield-limiting factors for improving wheat yield potential and closing the wheat yield gap. Our results revealed that wheat yield potential averaged 10.8 t ha–1in the recent decade. The low growing degree days(GDD) in the pre-winter growing season(592℃ d) and solar radiation in the whole growth season(3,036 MJ m–2) are the most critical climatic factors limiting wheat yield potential in the current production system. Nonetheless, wheat yield potential in the NCP is projected to decline during 2040–2059 by 1.8 and 5.1% under the representative concentration pathway(RCP) 4.5 and RCP8.5 scenarios, respectively, without considering the elevated CO_(2) concentration. However, the positive influence of CO_(2) fertilization will be sufficient to offset these negative impacts from climatic warming and solar dimming, ultimately leading to an enhancement in wheat yield potential during 2040–2059 by 7.5 and 9.8% compared to the baseline under RCP4.5 and RCP8.5, respectively. To improve the wheat yield potential, we recommend selecting an appropriate planting date(5 October) and planting density(400 plants m–2) that align with light and temperature conditions during the wheat growing season. In addition, optimizing the timing and rate of water application(three times, 270 mm) and fertilizer use(based on inseason root zone nitrogen management) is crucial for closing the wheat yield gap. This study underscores the importance of adopting multiple management practices that account for complex climate–crop–soil interconnections to enhance the wheat yield based on a long-term field experiment under the changing climate.展开更多
In extremely close-distance coal seam(ECDCS)mining,section coal pillars remain after upper coal seam(UCS)extraction.Thus,for layout and support design of lower coal seam(LCS)mining roadways,it is critical to account f...In extremely close-distance coal seam(ECDCS)mining,section coal pillars remain after upper coal seam(UCS)extraction.Thus,for layout and support design of lower coal seam(LCS)mining roadways,it is critical to account for UCS goaf deterioration and residual coal pillar(RCP)-induced stress disturbance.Taking the 6.4 m layer spacing of ECDCS mining in Nanyangpo Coal Mine as a case study,this research aimed to determine the optimal layout and surrounding rock control method for the 24202-ventilation roadway in the RCP area.First,the challenges of roadway layout and support under RCP were clarified:three layout methods face distinct RCPinduced stress disturbances and goaf-related roof damage.A finite element model was established;the second invariant of deviatoric stress(J_(2))and horizontal stress index were introduced to analyze plastic zone and stress evolution after UCS mining.Results show that J_(2)distributes symmetrically,with its peak diffusing downward and attenuating in a“/”-shaped pattern.Six schemes were simulated to compare plastic zone distributions at different positions,revealing that the optimal layout consists of a roadway alignment with the RCP center.Based on roadway layout and roof conditions,a cooperative control scheme was proposed:deep,strong anchorage with long cables across the RCP,and shallow stable support with short bolts in the ECDCS.This scheme secures roof cables anchored to the UCS RCP roof to achieve cross-seam anchorage.On-site borehole peeping and loose circle tests confirm smooth surrounding rock hole walls and limited failure range.Specifically,surrounding rock deformation and roof separation were controlled within 200 mm and 80 mm,respectively,with stable bolt/cable support resistance.These results offer an innovative solution for roadway layout design and support strategies under RCP in ECDCS,with significant engineering application value.展开更多
In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom bound...In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension.展开更多
The Jiangjia Gully, which is located in Dongchuan District, Yunnan Province, China, is a watershed prone to debris flows and has long-term recorded data of debris-flow occurrence. However, the initiation mechanism has...The Jiangjia Gully, which is located in Dongchuan District, Yunnan Province, China, is a watershed prone to debris flows and has long-term recorded data of debris-flow occurrence. However, the initiation mechanism has mainly been studied by experiments in this watershed. To further reveal debris-flow formation mechanism in the Jiangjia Gully, debris-flow activities in the initiation zone were observed with hand-held video cameras in the summer of 2016 and 2017. In these two years, six debris-flow events were triggered in Menqian Gully, a major tributary of the Jiangjia Gully, while debrisflow activities in some sub-watersheds of Menqian Gully were recorded with video cameras in four events. The video recording shows that landslides constituted an important source for sediment supply in debris flow. Some landslides directly evolved into debris flows, while the others released sediment into rills and channels, where debris flows were generated for sediment entrainment by water flow. Therefore, debris-flow occurrence in the Jiangjia Gully is influenced both by infiltration-dominated processes and by runoff-dominated processes. In addition, rainfall data from four gauges installed in Menqian Gully were analyzed using mean intensity(I), duration(D), peak 10-minute rainfall(R10min) and antecedent rainfall(AR) up to 15 days prior to peak 10-minute rainfall. It reveals that debris-flow triggering events can be discriminated from nontriggering events either by an I-D threshold or by an R10min-AR threshold. However, false alarms can be greatly reduced if these two kinds of thresholds are used together. Moreover, behaviors including intermittency of debris flow, variance in moisture content and volume among surges, and coalescence of multiple surges by temporary damming were observed, indicating the complexity of debris-flow initiation processes. These findings are expected to enhance our knowledge on debris-flow formation mechanism in regions with similar environmental settings.展开更多
To improve current understanding of the water cycle,energy partitioning and CO2 exchange over hilly zone vegetative land surfaces in the subtropical monsoon environment of southern China,a long-term field experiment o...To improve current understanding of the water cycle,energy partitioning and CO2 exchange over hilly zone vegetative land surfaces in the subtropical monsoon environment of southern China,a long-term field experiment observatory was set up at Ningxiang,eastern Hunan Province.This paper presents a preliminary analysis of the field observations at the observatory collected from August to November 2012.Results show that significant diurnal variations in soil temperature occur only in shallow soil layers(0.05,0.10,and 0.20 m),and that heavy rainfall affects soil moisture in the deep layers(≥ 0.40 m).During the experimental period,significant diurnal variations in albedo,radiation components,energy components,and CO2 flux were observed,but little seasonal variation.Strong photosynthesis in the vegetation canopy enhanced the CO2 absorption and the latent heat released in daylight hours;Latent heat of evaporation was the main consumer of available energy in late summer.Because the field experiment data are demonstrably reliable,the observatory will provide reliable long-term measurements for future investigations of the land-atmosphere interaction over hilly land surfaces in the subtropical monsoon region of southern China.展开更多
A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) r...A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) radicals into HO2 radicals.It can conduct different measurement modes through altering the reagent gases,achieving the speciated measurement of RO2 and RO2^#(RO2 radicals derived from the long-chain alkane,alkene and aromatic hydrocarbon).An example of field measurement results was given,with a maximum concentration of 1.88 × 10^(8) molecule/cm^(3) for RO2 and 1.18×10^(8) molecule/cm^(3) for RO2^(#).Also,this instrument quantifies the local ozone production rates directly,which can help to deduce the regional ozone control strategy from an experimental perspective.The new device can se rve as a potent tool for both the explo ration of frontier chemistry and the diagnosis of the control strategies.展开更多
Purpose： This paper focuses on the impact of social capital on urban children＇s use behavior of information communication technology （ICT）.Design/methodology/approach： Using the field survey and in-depth intervie...Purpose： This paper focuses on the impact of social capital on urban children＇s use behavior of information communication technology （ICT）.Design/methodology/approach： Using the field survey and in-depth interviews, we interviewed 40 children aged 6 to 12 and their parents from a staff residential quarter of the Zhengzhou University--＂Shengheyuan＂ community （SHY）, and a commercial residential quarter--＂Wanfenghuicheng＂ community （WFHC） in the high-tech zone of Zhengzhou City, Henan Province. We used the social capital theory to analyze the interviewees＇ record.Findings： In urban communities, social capital is the most important factor for children （aged 6 to 12） in their ICT use. Our findings indicate that children in families with higher levels of social capital, such as internal resources, family income, parent educational backgrounds and parents＇ social network, have more-highly developed ICT skills. Personal motivation and obstacles, such as lack of access to computers on a regular basis, also have an impact on children＇s ICT use. External social capital, including schools, libraries, and public service institutes, have little impact on children＇s ICT use, if not combined with internal social capital factors.Research limitations： Our research samples were collected from two communities within the same city, which may influence the generalization of this research result.Originality/value： To explore the social capital＇s influence on children＇s ICT use, we used field observation for ICT use of children aged 6 to 12 in urban communities in China, and studied the children＇s ICT behavior from the perspective of internal and external social capital.展开更多
Adverse weather conditions increase road risks;thus,weather testing is necessary to evaluate vehicle performance.Outdoor testing is the most realistic,but it is not as controlled,repeatable,and rapid as indoor testing...Adverse weather conditions increase road risks;thus,weather testing is necessary to evaluate vehicle performance.Outdoor testing is the most realistic,but it is not as controlled,repeatable,and rapid as indoor testing using an artificial precipitation system.However,outdoor data is still desirable for establishing the simulation targets on the vehicle surfaces.The dynamic-to-static precipitation intensity ratio is a useful parameter to correlate natural precipitation with perceived precipitation experienced by the moving vehicle.Theoretically,the amount of precipitation experienced by a translating surface depends on the orientation and travel speed.However,there are other external factors that could affect the perceived intensity,such as wind,turbulence,and droplet size distribution(DSD).Therefore,the existing simplified models evaluating a number of droplet strikes or precipitation flux calculated using natural precipitation density fail to have accurate predictions of the perceived precipitation rate,which hinders the evaluation vehicle application performance,such as sensor perception.In the present work,a semi-empirical prediction model is developed from the physics of precipitation in the context of vehicle aerodynamics and atmospheric dynamics.This model is validated with outdoor testing on a track for three days with rainy conditions.Multiple optical disdrometers are used to evaluate the precipitation rate experienced by a moving vehicle at different surface orientations through meteorological observations obtained in real-time from a nearby stationary meteorological tower and a moving vehicle.The data acquisition and processing methods are presented in detail.Results suggested that the proposed model is found to improve the current simplified mathematical expressions and is repeatable.It is found that improvements in prediction accuracy of perceived precipitation intensity compared to existing methods are usually more than 50%.展开更多
Thousands of lakes on the Tibetan Plateau(TP)play a critical role in the regional water cycle,weather,and climate.In recent years,the areas of TP lakes underwent drastic changes and have become a research hotspot.Howe...Thousands of lakes on the Tibetan Plateau(TP)play a critical role in the regional water cycle,weather,and climate.In recent years,the areas of TP lakes underwent drastic changes and have become a research hotspot.However,the characteristics of the lake-atmosphere interaction over the high-altitude lakes are still unclear,which inhibits model development and the accurate simulation of lake climate effects.The source region of the Yellow River(SRYR)has the largest outflow lake and freshwater lake on the TP and is one of the most densely distributed lakes on the TP.Since 2011,three observation sites have been set up in the Ngoring Lake basin in the SRYR to monitor the lake-atmosphere interaction and the differences among water-heat exchanges over the land and lake surfaces.This study presents an eight-year(2012–19),half-hourly,observation-based dataset related to lake–atmosphere interactions composed of three sites.The three sites represent the lake surface,the lakeside,and the land.The observations contain the basic meteorological elements,surface radiation,eddy covariance system,soil temperature,and moisture(for land).Information related to the sites and instruments,the continuity and completeness of data,and the differences among the observational results at different sites are described in this study.These data have been used in the previous study to reveal a few energy and water exchange characteristics of TP lakes and to validate and improve the lake and land surface model.The dataset is available at National Cryosphere Desert Data Center and Science Data Bank.展开更多
The climate variability induced by the El Nino-Southern Oscillation(ENSO)cycle drives significant changes in the physical state of the tropical Western Pacific,which has important impacts on the upper ocean carbon cyc...The climate variability induced by the El Nino-Southern Oscillation(ENSO)cycle drives significant changes in the physical state of the tropical Western Pacific,which has important impacts on the upper ocean carbon cycle.During 2015-2016,a super El Nino event occurred in the equatorial Pacific.Suspended particulate matter(SPM)data and related environmental observations in the tropical Western Pacific were obtained during two cruses in Dec.2014 and 2015,which coincided with the early and peak stages of this super El Nino event.Compared with the marine environments in the tropical Western Pacific in Dec.2014,an obviously enhanced upwelling occurred in the Mindanao Dome region;the nitrate concentration in the euphotic zone almo st tripled;and the size,mass concentration,and volume concentration of SPM obviously increased in Dec.2015.The enhanced upwelling in the Mindanao Dome region carried cold but eutrophic water upward from the deep ocean to shallow depths,even into the euphotic zone,which disrupted the previously N-limited conditions and induced a remarkable increase in phytoplankton blooms in the euphotic zone.The se results reveal the mechanism of how nutrient-limited ecosystems in the tropical Western Pacific respond to super El Nino events.In the context of the ENSO cycle,if predicted changes in biogenic particles occur,the proportion of carbon storage in the tropical Western Pacific is estimated to be increased by more than 52%,ultimately affecting the regional and possibly even global carbon cycle.This paper highlights the prospect for long-term prediction of the impact of a super El Nino event on the global carbon cycle and has profound implications for understanding El Nino events.展开更多
Structural relationships between the Neoproterozoic rock complexes of a continental massif,island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations with...Structural relationships between the Neoproterozoic rock complexes of a continental massif,island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations within the northeastern segment of the Central Taimyr tectonic zone distinguished in the late Hercynian fold-thrust belt of the Taimyr Peninsula.展开更多
The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013.The stud...The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013.The study suggests that the sediments were contributed from two major sources:the moraines and alluvial fans located in the Trans and Higher Himalaya;and the landslides in the Higher and Lesser Himalaya.Although the flood was the result of a high intensity rainfall event.展开更多
This study presents the utility of remote sensing （RS）, GIS and field observation data to estimate above ground biomass （AGB） and stem volume over tropical forest environment. Application of those data for the mod...This study presents the utility of remote sensing （RS）, GIS and field observation data to estimate above ground biomass （AGB） and stem volume over tropical forest environment. Application of those data for the modeling of forest properties is site specific and highly uncertain, thus further study is encouraged. In this study we used 1460 sampling plots collected in 16 transects measuring tree diameter （DBH） and other forest properties which were useful for the biomass assessment. The study was carded out in tropical forest region in East Kalimantan, Indo- nesia. The AGB density was estimated applying an existing DBH - biomass equation. The estimate was superimposed over the modified GIS map of the study area, and the biomass density of each land cover was calculated. The RS approach was performed using a subset of sample data to develop the AGB and stem volume linear equation models. Pearson correlation statistics test was conducted using ETM bands reflectance, vegetation indices, image transform layers, Principal Component Analysis （PCA） bands, Tasseled Cap （TC）, Grey Level Co-Occurrence Matrix （GLCM） texture features and DEM data as the predictors. Two linear models were generated from the significant RS data. To analyze total biomass and stem volume of each land cover, Landsat ETM images from 2000 and 2003 were preprocessed, classified using maximum likelihood method, and filtered with the majority analysis. We found 158±16 m^3.ha^-1 of stem volume and 168±15 t.ha^-1 of AGB estimated from RS approach, whereas the field measurement and GIS estimated 157±92 m^3.ha^-1 and 167±94 t.ha^-1 of stem volume and AGB, respectively. The dynamics of biomass abundance from 2000 to 2003 were assessed from multi temporal ETM data and we found a slightly declining trend of total biomass over these periods. Remote sensing approach estimated lower biomass abundance than did the GIS and field measurement data. The earlier approach predicted 10.5 Gt and 10.3 Gt of total biomasses in 2000 and 2003, while the later estimated 11.9 Gt and 11.6 Gt of total biomasses, respectively. We found that GLCM mean texture features showed markedly strong correlations with stem volume and biomass.展开更多
In this article,current research findings of local scour at offshore windfarm monopile foundations are presented.The scour mechanisms and scour depth prediction formulas under different hydrodynamic conditions are sum...In this article,current research findings of local scour at offshore windfarm monopile foundations are presented.The scour mechanisms and scour depth prediction formulas under different hydrodynamic conditions are summarized,including the current-only condition,wave-only condition,combined wave-current condition,and complex dynamic condition.Furthermore,this article analyzes the influencing factors on the basis of classical equations for predicting the equilibrium scour depth under specific conditions.The weakness of existing researches and future prospects are also discussed.It is suggested that future research shall focus on physical experiments under unsteady tidal currents or other complex loadings.The computational fluid dynamics-discrete element method and artificial intelligence technique are suggested being adopted to study the scour at offshore windfarm foundations.展开更多
基金the National Natural Science Foundation of China(41630636 and 41772325)China’s Second Tibetan Plateau Scientific Expedition and Research(2019QZKK0905).
文摘Crushed rock layers(CRLs),ventilation ducts(VDs)and thermosyphons are air-cooling structures(ACSs)widely used for maintaining the long-term stability of engineered infrastructures in permafrost environments.These ACSs can effectively cool and maintain the permafrost subgrade’s frozen state under climate warming by facilitating heat exchange with ambient air in cold seasons.As convection is a crucial working mechanism of these ACSs,it is imperative to understand the near-surface wind flow(NSWF)across a constructed infrastructure,such as an embankment.This article describes a yearlong field observation of the NSWF across an experimental expressway embankment,the first of its kind on the Qinghai–Tibet Plateau(QTP).The wind speed and direction along a transect perpendicular to the embankment on both the windward and leeward sides and at four different heights above the ground surface were collected and analyzed.The results showed that the embankment has a considerable impact on the NSWF speed within a distance of up to ten times its height,and in the direction on the leeward side.A power law can well describe the speed profiles of NSWF across the embankment,with the power-law indices(PLIs)varying from 0.14 to 0.40.On an annual basis,the fitted NSWF PLI far away from the embankment was 0.19,which differs substantially from the values widely used in previous thermal performance evaluations of ACSs on the QTP.Finally,the significance of the NSWF to the thermal performance of the ACSs,particularly the CRLs and VDs,in linear transportation infrastructure is discussed.It is concluded that underestimating the PLI and neglecting wind direction variations may lead to unconservative designs of the ACSs.The results reported in this study can provide valuable guidance for infrastructure engineering on the QTP and other similar permafrost regions.
基金supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No.42325502)the 2nd Scientific Expedition to the Qinghai–Tibet Plateau (Grant No.2019QZKK0102)+3 种基金the West Light Foundation of the Chinese Academy of Sciences (Grant No.xbzg-zdsys-202215)the Science and Technology Research Plan of Gansu Province (Grant Nos.23JRRA654 and 20JR10RA070)the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No.QCH2019004)iLEAPS (integrated Land Ecosystem–Atmosphere Processes Study)。
文摘The source region of the Yellow River, accounting for over 38% of its total runoff, is a critical catchment area,primarily characterized by alpine grasslands. In 2005, the Maqu land surface processes observational site was established to monitor climate, land surface dynamics, and hydrological variability in this region. Over a 10-year period(2010–19), an extensive observational dataset was compiled, now available to the scientific community. This dataset includes comprehensive details on site characteristics, instrumentation, and data processing methods, covering meteorological and radiative fluxes, energy exchanges, soil moisture dynamics, and heat transfer properties. The dataset is particularly valuable for researchers studying land surface processes, land–atmosphere interactions, and climate modeling, and may also benefit ecological, hydrological, and water resource studies. The report ends with a discussion on perspectives and challenges of continued observational monitoring in this region, focusing on issues such as cryosphere influences, complex topography,and ecological changes like the encroachment of weeds and scrubland.
基金supported by National Natural Science Foundation of China(No.61862038)Lanzhou Talent Innovation and Entrepreneurship Technology Plan Project(No.2019-RC-14).
文摘Aiming at node deployment in the monitoring area of the field observation instrument network in the cold and arid regions,we propose a virtual force algorithm based on Voronoi diagram(VFAVD),which adopts probabilistic sensing model that is more in line with the actual situation.First,the Voronoi diagram is constructed in the monitoring area to determine the Thiessen polygon of each node.Then,the virtual force on each node is calculated,and the node update its position according to the direction and size of the total force,so as to achieve the purpose of improving the network coverage rate.The simulation results show that the proposed algorithm can effectively improve the coverage rate of the network,and also has a good effect on the coverage uniformity.
文摘Radio observations of some active regions (ARs) obtained with the Nobeyama radioheliograph at λ=1.76 cm are used for estimating the magnetic field strength in the upper chromosphere, based on thermal bremsstrahlung. The results are compared with the magnetic field strength in the photosphere from observations with the Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station of Beijing Astronomical Observatory. The difference in the magnetic field strength between the two layers seems reasonable. The solar radio maps of active regions obtained with the Nobeyama radioheliograph, both in total intensity (I-map) and in circular polarizations (V-map), are compared with the optical magnetograms obtained with the SMFT. The comparison between the radio map in circular polarization and the longitudinal photospheric magnetogram of a plage region suggests that the radio map in circular polarization is a kind of magnetogram of the upper chromosphere. The comparison of the radio map in total intensity with the photo-spheric vector magnetogram of an AR shows that the radio map in total intensity gives indications of magnetic loops in the corona, thus we have a method of defining the coronal magnetic structure from the radio I-maps at λ=1.76 cm. Analysing the I-maps, we identified three components: (a) a compact bright source; (b) a narrow elongated structure connecting two main magnetic islands of opposite polarities (observed in both the optical and radio magnetograms); (c) a wide, diffuse, weak component that corresponds to a wide structure in the solar active region which shows in most cases an S or a reversed S contour, which is probably due to the differential rotation of the Sun. The last two components suggest coronal loops on different spatial scales above the neutral line of the longitudinal photospheric magnetic field.
基金This research was funded by the Fellowship of the China Postdoctoral Science Foundation(2021M703466)the Basic Research Innovation Group Project of Gansu Province,China(21JR7RA347)the Natural Science Foundation of Gansu Province,China(20JR10RA231).
文摘Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.
文摘The Macao Science Satellite-1(MSS-1)is the first space science satellite jointly developed on the Chinese mainland and in Macao region.It comprises two satellites,named MSS-1A and MSS-1B,and holds considerable importance in China’s space exploration endeavors.Among these,MSS-1A is the world’s first high-precision scientific satellite dedicated to exploring the geomagnetic field and space environment at low latitudes.Equipped with two high-precision vector magnetometers and one scalar magnetometer,which are integrally installed on a highly stable nonmagnetic optical bench,the MSS-1A enables simultaneous high-precision measurements of both the Earth’s vector magnetic field and its scalar components.Its design integrates several state-of-the-art technologies,including arc-second-level thermal stability control,nonmagnetic thermal control for the optical bench,and ultra-high magnetic cleanliness control.These innovations effectively minimize magnetic interference originating from the satellite itself,thereby substantially improving the precision of geomagnetic field measurements and establishing a robust technical foundation for future magnetic survey satellite constellations.
基金supported by the National Key Research and Development Program of China (2023YFD2302801)the Central Public-interest Scientific Institution Basal Research Fund of Chinese Academy of Agricultural Sciences (JBYW-AII-2024-38)+1 种基金the Fundamental Research Funds for the Central UniversitiesChina Scholarship Council。
文摘Accurately estimating the wheat yield potential under climate changes is essential for assessing food production capacity. However, studies based on crop modeling and imperfect management experiment data frequently underestimate the wheat yield potential. In this study, we evaluated wheat yield potential based on the CERES-Wheat model and a well-managed 10-year(2008–2017) field study in the North China Plain(NCP), and further identified the critical climate and management yield-limiting factors for improving wheat yield potential and closing the wheat yield gap. Our results revealed that wheat yield potential averaged 10.8 t ha–1in the recent decade. The low growing degree days(GDD) in the pre-winter growing season(592℃ d) and solar radiation in the whole growth season(3,036 MJ m–2) are the most critical climatic factors limiting wheat yield potential in the current production system. Nonetheless, wheat yield potential in the NCP is projected to decline during 2040–2059 by 1.8 and 5.1% under the representative concentration pathway(RCP) 4.5 and RCP8.5 scenarios, respectively, without considering the elevated CO_(2) concentration. However, the positive influence of CO_(2) fertilization will be sufficient to offset these negative impacts from climatic warming and solar dimming, ultimately leading to an enhancement in wheat yield potential during 2040–2059 by 7.5 and 9.8% compared to the baseline under RCP4.5 and RCP8.5, respectively. To improve the wheat yield potential, we recommend selecting an appropriate planting date(5 October) and planting density(400 plants m–2) that align with light and temperature conditions during the wheat growing season. In addition, optimizing the timing and rate of water application(three times, 270 mm) and fertilizer use(based on inseason root zone nitrogen management) is crucial for closing the wheat yield gap. This study underscores the importance of adopting multiple management practices that account for complex climate–crop–soil interconnections to enhance the wheat yield based on a long-term field experiment under the changing climate.
基金supported by the National Natural Science Foundation of China(No.52074296)。
文摘In extremely close-distance coal seam(ECDCS)mining,section coal pillars remain after upper coal seam(UCS)extraction.Thus,for layout and support design of lower coal seam(LCS)mining roadways,it is critical to account for UCS goaf deterioration and residual coal pillar(RCP)-induced stress disturbance.Taking the 6.4 m layer spacing of ECDCS mining in Nanyangpo Coal Mine as a case study,this research aimed to determine the optimal layout and surrounding rock control method for the 24202-ventilation roadway in the RCP area.First,the challenges of roadway layout and support under RCP were clarified:three layout methods face distinct RCPinduced stress disturbances and goaf-related roof damage.A finite element model was established;the second invariant of deviatoric stress(J_(2))and horizontal stress index were introduced to analyze plastic zone and stress evolution after UCS mining.Results show that J_(2)distributes symmetrically,with its peak diffusing downward and attenuating in a“/”-shaped pattern.Six schemes were simulated to compare plastic zone distributions at different positions,revealing that the optimal layout consists of a roadway alignment with the RCP center.Based on roadway layout and roof conditions,a cooperative control scheme was proposed:deep,strong anchorage with long cables across the RCP,and shallow stable support with short bolts in the ECDCS.This scheme secures roof cables anchored to the UCS RCP roof to achieve cross-seam anchorage.On-site borehole peeping and loose circle tests confirm smooth surrounding rock hole walls and limited failure range.Specifically,surrounding rock deformation and roof separation were controlled within 200 mm and 80 mm,respectively,with stable bolt/cable support resistance.These results offer an innovative solution for roadway layout design and support strategies under RCP in ECDCS,with significant engineering application value.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51061130546 and 51379127)the Key Projects in the National Science&Technology Pillar Program(Grant No.2012BAC07B02)
文摘In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension.
基金financially supported by the National Key Research and Development Program of China(2020YFD1100701)the Science and Technology Research and Development Program of China Railway(K2019G006)the Chongqing Municipal Bureau of Land,Resources and Housing Administration(KJ-2021016)。
文摘The Jiangjia Gully, which is located in Dongchuan District, Yunnan Province, China, is a watershed prone to debris flows and has long-term recorded data of debris-flow occurrence. However, the initiation mechanism has mainly been studied by experiments in this watershed. To further reveal debris-flow formation mechanism in the Jiangjia Gully, debris-flow activities in the initiation zone were observed with hand-held video cameras in the summer of 2016 and 2017. In these two years, six debris-flow events were triggered in Menqian Gully, a major tributary of the Jiangjia Gully, while debrisflow activities in some sub-watersheds of Menqian Gully were recorded with video cameras in four events. The video recording shows that landslides constituted an important source for sediment supply in debris flow. Some landslides directly evolved into debris flows, while the others released sediment into rills and channels, where debris flows were generated for sediment entrainment by water flow. Therefore, debris-flow occurrence in the Jiangjia Gully is influenced both by infiltration-dominated processes and by runoff-dominated processes. In addition, rainfall data from four gauges installed in Menqian Gully were analyzed using mean intensity(I), duration(D), peak 10-minute rainfall(R10min) and antecedent rainfall(AR) up to 15 days prior to peak 10-minute rainfall. It reveals that debris-flow triggering events can be discriminated from nontriggering events either by an I-D threshold or by an R10min-AR threshold. However, false alarms can be greatly reduced if these two kinds of thresholds are used together. Moreover, behaviors including intermittency of debris flow, variance in moisture content and volume among surges, and coalescence of multiple surges by temporary damming were observed, indicating the complexity of debris-flow initiation processes. These findings are expected to enhance our knowledge on debris-flow formation mechanism in regions with similar environmental settings.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA05110102)the National Natural Science Foundation of China (Grant No.41075062)the National Basic Research Program of China (Grant No. 2010CB951001)
文摘To improve current understanding of the water cycle,energy partitioning and CO2 exchange over hilly zone vegetative land surfaces in the subtropical monsoon environment of southern China,a long-term field experiment observatory was set up at Ningxiang,eastern Hunan Province.This paper presents a preliminary analysis of the field observations at the observatory collected from August to November 2012.Results show that significant diurnal variations in soil temperature occur only in shallow soil layers(0.05,0.10,and 0.20 m),and that heavy rainfall affects soil moisture in the deep layers(≥ 0.40 m).During the experimental period,significant diurnal variations in albedo,radiation components,energy components,and CO2 flux were observed,but little seasonal variation.Strong photosynthesis in the vegetation canopy enhanced the CO2 absorption and the latent heat released in daylight hours;Latent heat of evaporation was the main consumer of available energy in late summer.Because the field experiment data are demonstrably reliable,the observatory will provide reliable long-term measurements for future investigations of the land-atmosphere interaction over hilly land surfaces in the subtropical monsoon region of southern China.
基金the National Key R&D Program of China(No.2017YFC0209402)the Beijing Natural Science Foundation,China(No.JQ19031)。
文摘A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) radicals into HO2 radicals.It can conduct different measurement modes through altering the reagent gases,achieving the speciated measurement of RO2 and RO2^#(RO2 radicals derived from the long-chain alkane,alkene and aromatic hydrocarbon).An example of field measurement results was given,with a maximum concentration of 1.88 × 10^(8) molecule/cm^(3) for RO2 and 1.18×10^(8) molecule/cm^(3) for RO2^(#).Also,this instrument quantifies the local ozone production rates directly,which can help to deduce the regional ozone control strategy from an experimental perspective.The new device can se rve as a potent tool for both the explo ration of frontier chemistry and the diagnosis of the control strategies.
文摘Purpose： This paper focuses on the impact of social capital on urban children＇s use behavior of information communication technology （ICT）.Design/methodology/approach： Using the field survey and in-depth interviews, we interviewed 40 children aged 6 to 12 and their parents from a staff residential quarter of the Zhengzhou University--＂Shengheyuan＂ community （SHY）, and a commercial residential quarter--＂Wanfenghuicheng＂ community （WFHC） in the high-tech zone of Zhengzhou City, Henan Province. We used the social capital theory to analyze the interviewees＇ record.Findings： In urban communities, social capital is the most important factor for children （aged 6 to 12） in their ICT use. Our findings indicate that children in families with higher levels of social capital, such as internal resources, family income, parent educational backgrounds and parents＇ social network, have more-highly developed ICT skills. Personal motivation and obstacles, such as lack of access to computers on a regular basis, also have an impact on children＇s ICT use. External social capital, including schools, libraries, and public service institutes, have little impact on children＇s ICT use, if not combined with internal social capital factors.Research limitations： Our research samples were collected from two communities within the same city, which may influence the generalization of this research result.Originality/value： To explore the social capital＇s influence on children＇s ICT use, we used field observation for ICT use of children aged 6 to 12 in urban communities in China, and studied the children＇s ICT behavior from the perspective of internal and external social capital.
基金the financial support of the Natural Sciences and Engineering Research Council of Canada(NSERC)。
文摘Adverse weather conditions increase road risks;thus,weather testing is necessary to evaluate vehicle performance.Outdoor testing is the most realistic,but it is not as controlled,repeatable,and rapid as indoor testing using an artificial precipitation system.However,outdoor data is still desirable for establishing the simulation targets on the vehicle surfaces.The dynamic-to-static precipitation intensity ratio is a useful parameter to correlate natural precipitation with perceived precipitation experienced by the moving vehicle.Theoretically,the amount of precipitation experienced by a translating surface depends on the orientation and travel speed.However,there are other external factors that could affect the perceived intensity,such as wind,turbulence,and droplet size distribution(DSD).Therefore,the existing simplified models evaluating a number of droplet strikes or precipitation flux calculated using natural precipitation density fail to have accurate predictions of the perceived precipitation rate,which hinders the evaluation vehicle application performance,such as sensor perception.In the present work,a semi-empirical prediction model is developed from the physics of precipitation in the context of vehicle aerodynamics and atmospheric dynamics.This model is validated with outdoor testing on a track for three days with rainy conditions.Multiple optical disdrometers are used to evaluate the precipitation rate experienced by a moving vehicle at different surface orientations through meteorological observations obtained in real-time from a nearby stationary meteorological tower and a moving vehicle.The data acquisition and processing methods are presented in detail.Results suggested that the proposed model is found to improve the current simplified mathematical expressions and is repeatable.It is found that improvements in prediction accuracy of perceived precipitation intensity compared to existing methods are usually more than 50%.
基金supported by the National Natural Science Foundations of China(Grant Nos.41930759,41822501,42075089,41975014)the 2nd Scientific Expedition to the Qinghai-Tibet Plateau(2019QZKK0102)+3 种基金The Science and Technology Research Plan of Gansu Province(20JR10RA070)the Chinese Academy of Youth Innovation and Promotion,CAS(Y201874)the Youth Innovation Promotion Association CAS(QCH2019004)iLEAPs(Integrated Land Ecosystem-Atmosphere Processes Study-iLEAPS)。
文摘Thousands of lakes on the Tibetan Plateau(TP)play a critical role in the regional water cycle,weather,and climate.In recent years,the areas of TP lakes underwent drastic changes and have become a research hotspot.However,the characteristics of the lake-atmosphere interaction over the high-altitude lakes are still unclear,which inhibits model development and the accurate simulation of lake climate effects.The source region of the Yellow River(SRYR)has the largest outflow lake and freshwater lake on the TP and is one of the most densely distributed lakes on the TP.Since 2011,three observation sites have been set up in the Ngoring Lake basin in the SRYR to monitor the lake-atmosphere interaction and the differences among water-heat exchanges over the land and lake surfaces.This study presents an eight-year(2012–19),half-hourly,observation-based dataset related to lake–atmosphere interactions composed of three sites.The three sites represent the lake surface,the lakeside,and the land.The observations contain the basic meteorological elements,surface radiation,eddy covariance system,soil temperature,and moisture(for land).Information related to the sites and instruments,the continuity and completeness of data,and the differences among the observational results at different sites are described in this study.These data have been used in the previous study to reveal a few energy and water exchange characteristics of TP lakes and to validate and improve the lake and land surface model.The dataset is available at National Cryosphere Desert Data Center and Science Data Bank.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB42010203,XDA19060401,XDA23050503)the Science&Technology Basic Resources Investigation Program of China(No.2017FY100802)+1 种基金the Open Fund for Key Laboratory of Mar.Geol.and Environment,Institute of Oceanology,Chinese Academy of Sciences(No.MGE2019KG03)the Qingdao(Laoshan)Postdoctoral Applied Research Proj ect in 2019(No.Y9KY161)。
文摘The climate variability induced by the El Nino-Southern Oscillation(ENSO)cycle drives significant changes in the physical state of the tropical Western Pacific,which has important impacts on the upper ocean carbon cycle.During 2015-2016,a super El Nino event occurred in the equatorial Pacific.Suspended particulate matter(SPM)data and related environmental observations in the tropical Western Pacific were obtained during two cruses in Dec.2014 and 2015,which coincided with the early and peak stages of this super El Nino event.Compared with the marine environments in the tropical Western Pacific in Dec.2014,an obviously enhanced upwelling occurred in the Mindanao Dome region;the nitrate concentration in the euphotic zone almo st tripled;and the size,mass concentration,and volume concentration of SPM obviously increased in Dec.2015.The enhanced upwelling in the Mindanao Dome region carried cold but eutrophic water upward from the deep ocean to shallow depths,even into the euphotic zone,which disrupted the previously N-limited conditions and induced a remarkable increase in phytoplankton blooms in the euphotic zone.The se results reveal the mechanism of how nutrient-limited ecosystems in the tropical Western Pacific respond to super El Nino events.In the context of the ENSO cycle,if predicted changes in biogenic particles occur,the proportion of carbon storage in the tropical Western Pacific is estimated to be increased by more than 52%,ultimately affecting the regional and possibly even global carbon cycle.This paper highlights the prospect for long-term prediction of the impact of a super El Nino event on the global carbon cycle and has profound implications for understanding El Nino events.
文摘Structural relationships between the Neoproterozoic rock complexes of a continental massif,island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations within the northeastern segment of the Central Taimyr tectonic zone distinguished in the late Hercynian fold-thrust belt of the Taimyr Peninsula.
文摘The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013.The study suggests that the sediments were contributed from two major sources:the moraines and alluvial fans located in the Trans and Higher Himalaya;and the landslides in the Higher and Lesser Himalaya.Although the flood was the result of a high intensity rainfall event.
文摘This study presents the utility of remote sensing （RS）, GIS and field observation data to estimate above ground biomass （AGB） and stem volume over tropical forest environment. Application of those data for the modeling of forest properties is site specific and highly uncertain, thus further study is encouraged. In this study we used 1460 sampling plots collected in 16 transects measuring tree diameter （DBH） and other forest properties which were useful for the biomass assessment. The study was carded out in tropical forest region in East Kalimantan, Indo- nesia. The AGB density was estimated applying an existing DBH - biomass equation. The estimate was superimposed over the modified GIS map of the study area, and the biomass density of each land cover was calculated. The RS approach was performed using a subset of sample data to develop the AGB and stem volume linear equation models. Pearson correlation statistics test was conducted using ETM bands reflectance, vegetation indices, image transform layers, Principal Component Analysis （PCA） bands, Tasseled Cap （TC）, Grey Level Co-Occurrence Matrix （GLCM） texture features and DEM data as the predictors. Two linear models were generated from the significant RS data. To analyze total biomass and stem volume of each land cover, Landsat ETM images from 2000 and 2003 were preprocessed, classified using maximum likelihood method, and filtered with the majority analysis. We found 158±16 m^3.ha^-1 of stem volume and 168±15 t.ha^-1 of AGB estimated from RS approach, whereas the field measurement and GIS estimated 157±92 m^3.ha^-1 and 167±94 t.ha^-1 of stem volume and AGB, respectively. The dynamics of biomass abundance from 2000 to 2003 were assessed from multi temporal ETM data and we found a slightly declining trend of total biomass over these periods. Remote sensing approach estimated lower biomass abundance than did the GIS and field measurement data. The earlier approach predicted 10.5 Gt and 10.3 Gt of total biomasses in 2000 and 2003, while the later estimated 11.9 Gt and 11.6 Gt of total biomasses, respectively. We found that GLCM mean texture features showed markedly strong correlations with stem volume and biomass.
基金supported by the Major International Joint Research Project P0W3M of the National Natural Science Foundation of China(Grant No.51920105013)the General Project of the National Natural Science Foundation of China(Grant No.52071127).
文摘In this article,current research findings of local scour at offshore windfarm monopile foundations are presented.The scour mechanisms and scour depth prediction formulas under different hydrodynamic conditions are summarized,including the current-only condition,wave-only condition,combined wave-current condition,and complex dynamic condition.Furthermore,this article analyzes the influencing factors on the basis of classical equations for predicting the equilibrium scour depth under specific conditions.The weakness of existing researches and future prospects are also discussed.It is suggested that future research shall focus on physical experiments under unsteady tidal currents or other complex loadings.The computational fluid dynamics-discrete element method and artificial intelligence technique are suggested being adopted to study the scour at offshore windfarm foundations.
