In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fr...In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific,is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products.Mooring observations were conducted from September 13,2017 to August 15,2018 in the COMRA contact area(10°N,154°W).The results were as follows:(1)At depths below 200 m,the kinetic energy of intra-seasonal variability(20-100 d)accounts for more than 40%of the overall low-frequency variability,while the ratio reaches more than 50%below 2000 m.(2)At depths below 200 m,currents show a synchronous oscillation with a characteristic time scale of 30 d,lasting from October to the following January;the energy of the 30-d oscillation increases with depth until the layer of approximately 4616 m,and the maximum velocity is approximately 10 cm/s.(3)The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.展开更多
Climate change has led human beings to take an interest in the study of meteorological and climatic phenomena. In fact, the main impact of climate change on different sectors of society is caused by extreme events sin...Climate change has led human beings to take an interest in the study of meteorological and climatic phenomena. In fact, the main impact of climate change on different sectors of society is caused by extreme events since the occurrence of extreme events leads to more impact related to change in mean climate. Unfortunately, the West African region is vulnerable to extreme rainfall impact because its economy is based on rain-fed agriculture. This study examined the seasonal variability of extreme rainfall in West Africa. Eight (8) climate indices were chosen from among the 27 defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). The nonparametric Mann-Kendall test was used to assess the seasonal trends. The indices of the same types (frequency or intensity) were compared to assess the intra-seasonal variation of extreme precipitation. The results indicate that, regardless of the season, the Gulf of Guinea receives more rainfall than the Sahel. This phenomenon is due to the fact that the coastal part of West Africa is under the influence of evaporation which is observed at the Atlantic Ocean and during the monsoon, while the other part is dominated by the desert. Mann-Kendall’s test revealed upward and downward trends during each season. The increase in extreme rainfall trends in the number of consecutive dry days suggests that droughts, due to global warming, could be observed and could have severe consequences in terms of water availability, energy supply, agricultural yields and ecosystems in West Africa. In addition, it can lead to the loss of biodiversity and health issues. It is therefore essential for policymakers or decisions makers to determine strategies and mitigation measures against climate change and its impacts on populations.展开更多
The study of temporal and spatial distribution of ozone is very important for understanding the atmospheric chemistry and thereby its impact on environment, weather and climate. The intra-seasonal variability plays a ...The study of temporal and spatial distribution of ozone is very important for understanding the atmospheric chemistry and thereby its impact on environment, weather and climate. The intra-seasonal variability plays a major role in the inter-annual variability of weather parameters such as rainfall, temperature, pressure and atmospheric trace gas constituents such as atmospheric ozone. The strength of monsoon circulation and deep convection greatly modifies the atmospheric compositions and meteorological parameters such as rainfall amount, distributions of atmospheric trace gas concentrations and other weather parameters over the summer monsoon region. The daily total column ozone (TCO) measured over maritime station (Lakshadweep Island— 10°10'N & 73°30'E) and coastal station (Cochin—9°55'N and 76°16'E) using Microtop II Ozonometer were considered for the comparative study of seasonal and intra-seasonal variability for the year 2015. The annual average of total column ozone over Lakshadweep Islands and Cochin was 290 DU and 280 DU respectively for the year 2015. The greater concentrations in daily TCO measurements over Lakshadweep Islands for all seasons compared to Cochin lead to the speculations that, the surface ozone concentration is more because of pollution from the diesel burning emissions, since the whole Island’s population completely depends on diesel generator for the power supply. During winter season maritime station shows a decrease of ~30 DU in TCO over Lak-shadweep Island compared to coastal station Cochin (~18 DU) from the annual mean in the month of December. During pre-monsoon season TCO concentration is high over both locations. There is gradual increase of TCO concentration over Cochin from pre-monsoon to monsoon season and peak in the month of September, but decreasing TCO concentrations measured over Lakshadweep during July to August. In the analysis it was found that Intra-Seasonal Variability (ISV) in total column ozone over Lakshadweep Islands and Cochin during summer monsoon season was modulated by the monsoon dynamics and convection, thereby changes in the photochemistry of ozone production and distributions over the monsoon region. Two significant intra-seasonal oscillations (ISOs) such as Madden Julian Oscillation (MJO) and Quasi-Biweekly Oscillations (QBW) were identified in the TCO during monsoon season. The MJO shows higher periodicity (~54 days) over Lakshadweep Islands compared to the coastal station, Cochin (~48 days). Intra-seasonal variability of TCO over the maritime and coastal stations varies with geographic locations, marine boundary layer characteristics and also with seasons. The intra-seasonal variability or ISOs controls the interannual variability of TCO over a region. Hence deeper knowledge of ISOs in trace gases such as ozone helps us to understand more about the regional climate and air quality.展开更多
Sub-seasonal prediction of regional compound heatwaves and their predictability sources remain unclear.In this study,the underlying mechanisms for the long-lasting compound heatwave over Southern China during July 1–...Sub-seasonal prediction of regional compound heatwaves and their predictability sources remain unclear.In this study,the underlying mechanisms for the long-lasting compound heatwave over Southern China during July 1–18,2010,and the major sources of its sub-seasonal prediction skill are identified.The results show that both the development and decay of this compound heatwave are mainly dominated by atmospheric processes(i.e.,adiabatic heating associated with anticyclonic circulation),whereas land-atmosphere coupling processes play an important role in sustaining the heatwave.A further analysis indicates that by inducing anomalous anticyclonic circulations over Southern China,the tropical intraseasonal oscillations with periods of 30–60 days and 10–30 days facilitate the occurrence and maintenance of the heatwave during its entire and second half periods,respectively.The NCEP Climate Forecast System Version 2 shows a low skill in predicting the 2010 compound heatwave over Southern China when the lead time is longer than 2 pentads,which is largely attributed to the model’s bias in representing the intensity and phase of intra-seasonal oscillations.展开更多
In this paper,we establish some strong laws of large numbers,which are for nonindependent random variables under the framework of sublinear expectations.One of our main results is for blockwise m-dependent random vari...In this paper,we establish some strong laws of large numbers,which are for nonindependent random variables under the framework of sublinear expectations.One of our main results is for blockwise m-dependent random variables,and another is for sub-orthogonal random variables.Both extend the strong law of large numbers for independent random variables under sublinear expectations to the non-independent case.展开更多
In this paper,we consider the fourth-order parabolic equation with p(x)Laplacian and variable exponent source ut+∆^(2)u−div(|■u|^(p(x)−2■u))=|u|^(q(x))−1u.By applying potential well method,we obtain global existence...In this paper,we consider the fourth-order parabolic equation with p(x)Laplacian and variable exponent source ut+∆^(2)u−div(|■u|^(p(x)−2■u))=|u|^(q(x))−1u.By applying potential well method,we obtain global existence,asymptotic behavior and blow-up of solutions with initial energy J(u_(0))≤d.Moreover,we estimate the upper bound of the blow-up time for J(u_(0))≤0.展开更多
Tree growth variability is a key determinant of forest stabilities.Previous studies have shown that recent climate change has increased variability in tree growth,while others have challenged this viewpoint,leading to...Tree growth variability is a key determinant of forest stabilities.Previous studies have shown that recent climate change has increased variability in tree growth,while others have challenged this viewpoint,leading to ongoing debate in this field.Moreover,gaps remain in understanding the climatic mechanisms driving increased tree growth variability,particularly for species simultaneously limited by multiple climate factors.In this study,we assessed the temporal trends in variability of Picea purpurea radial growth and its linkage with growth-climate sensitivity utilizing dendrochronological methods.Our results revealed a significant increase in P.purpurea radial growth variability from 1960 to 2020,as indicated by continuous rises in the standard deviation,coefficient of variation,and mean sensitivity of tree-ring width indices.The increased frequency of extreme growth declines further supported this finding.Furthermore,moisture condition in July was identified as a key limiting factor of P.purpurea growth.Notably,the strengthening relationship between tree-ring width indices and vapor pressure deficit(VPD)suggests that the moisture sensitivity for P.purpurea growth has increased over the period 1960-2020.This enhanced sensitivity to VPD,whose interannual variability has also increased synchronously,may have contributed to the rise in P.purpurea growth variability.Additionally,the maximum temperature in May was positively correlated with P.purpurea growth;however,there is little evidence that this factor contributed to the observed increase in growth variability.These findings provide new insights into P.purpurea growth trends and improve our understanding of the potential future impacts of climate change on forest ecosystems.展开更多
As a vital food crop,rice is an important part of global food crops.Studying the spatiotemporal changes in rice cultivation facilitates early prediction of production risks and provides support for agricultural policy...As a vital food crop,rice is an important part of global food crops.Studying the spatiotemporal changes in rice cultivation facilitates early prediction of production risks and provides support for agricultural policy decisions related to rice.With the increasing application of satellite remote sensing technology in crop monitoring,remote sensing for rice cultivation has emerged as a novel approach,offering new perspectives for monitoring rice planting.This paper briefly outlined the current research and development status of satellite remote sensing for monitoring rice cultivation both at home and abroad.Foreign scholars have made innovations in data sources and methodologies for satellite remote sensing monitoring,and utilized multi-source satellite information and machine learning algorithms to enhance the accuracy of rice planting monitoring.Scholars in China have achieved significant results in the study of satellite remote sensing for monitoring rice cultivation.Their research and application in monitoring rice planting areas provide valuable references for agricultural production management.However,satellite remote sensing monitoring of rice still faces challenges such as low spatiotemporal resolution and difficulties related to cloud cover and data fusion,which require further in-depth investigation.Additionally,there are shortcomings in the accuracy of remote sensing monitoring for fragmented farmland plots and smallholder farming.To address these issues,future efforts should focus on developing multi-source heterogeneous data fusion analysis technologies and researching monitoring systems.These advancements are expected to enable high-precision large-scale acquisition of rice planting information,laying a foundation for future smart agriculture.展开更多
Thermal-mechanical damage and deformation at the interface between shotcrete linings and the surrounding rock of tunnels under high-temperature and variable-temperature conditions are critical to the safe construction...Thermal-mechanical damage and deformation at the interface between shotcrete linings and the surrounding rock of tunnels under high-temperature and variable-temperature conditions are critical to the safe construction and operation of tunnel engineering.This study investigated the thermo-mechanical damage behavior of the composite interface between alkali-resistant glass fiber-reinforced concrete(ARGFRC)and granite,focusing on a plateau railway tunnel.Laboratory triaxial tests,laser scanning,XRD analysis,numerical simulations,and theoretical analyses were employed to investigate how different initial curing temperatures and joint roughness coefficient(JRC)influence interfacial damage behavior.The results indicate that an increase in interface roughness exacerbates the structural damage at the interface.At a JRC of 19.9 and a temperature of 70℃,crack initiation in granite was notably restrained when the confining pressure rose from 7 MPa to 10 MPa.Roughness-induced stress distribution at the interface was notably altered,although this effect became less pronounced under high confining pressure conditions.Additionally,during high-temperature curing,thermal stress concentration at the tips of micro-convex protrusions on the granite surface induced microcracks in the adjacent ARGFRC matrix,followed by deformation.These findings provide practical guidelines for designing concrete support systems to ensure tunnel structural safety in high-altitude regions with harsh thermal environments.展开更多
Marine forecasting is critical for navigation safety and disaster prevention.However,traditional ocean numerical forecasting models are often limited by substantial errors and inadequate capture of temporal-spatial fe...Marine forecasting is critical for navigation safety and disaster prevention.However,traditional ocean numerical forecasting models are often limited by substantial errors and inadequate capture of temporal-spatial features.To address the limitations,the paper proposes a TimeXer-based numerical forecast correction model optimized by an exogenous-variable attention mechanism.The model treats target forecast values as internal variables,and incorporates historical temporal-spatial data and seven-day numerical forecast results from traditional models as external variables based on the embedding strategy of TimeXer.Using a self-attention structure,the model captures correlations between exogenous variables and target sequences,explores intrinsic multi-dimensional relationships,and subsequently corrects endogenous variables with the mined exogenous features.The model’s performance is evaluated using metrics including MSE(Mean Squared Error),MAE(Mean Absolute Error),RMSE(Root Mean Square Error),MAPE(Mean Absolute Percentage Error),MSPE(Mean Square Percentage Error),and computational time,with TimeXer and PatchTST models serving as benchmarks.Experiment results show that the proposed model achieves lower errors and higher correction accuracy for both one-day and seven-day forecasts.展开更多
Energy shortage has become one of themost concerning issues in the world today,and improving energy utilization efficiency is a key area of research for experts and scholars worldwide.Small-diameter heat exchangers of...Energy shortage has become one of themost concerning issues in the world today,and improving energy utilization efficiency is a key area of research for experts and scholars worldwide.Small-diameter heat exchangers offer advantages such as reduced material usage,lower refrigerant charge,and compact structure.However,they also face challenges,including increased refrigerant pressure drop and smaller heat transfer area inside the tubes.This paper combines the advantages and disadvantages of both small and large-diameter tubes and proposes a combined-diameter heat exchanger,consisting of large and small diameters,for use in the indoor units of split-type air conditioners.There are relatively few studies in this area.In this paper,A theoretical and numerical computation method is employed to establish a theoretical-numerical calculation model,and its reliability is verified through experiments.Using this model,the optimal combined diameters and flow path design for a combined-diameter heat exchanger using R32 as the working fluid are derived.The results show that the heat transfer performance of all combined diameter configurations improves by 2.79%to 8.26%compared to the baseline design,with the coefficient of performance(COP)increasing from 4.15 to 4.27~4.5.These designs can save copper material,but at the cost of an increase in pressure drop by 66.86%to 131.84%.The scheme IIIH,using R32,is the optimal combined-diameter and flow path configuration that balances both heat transfer performance and economic cost.展开更多
Tuberculosis(TB),one of the oldest infectious diseases caused by Mycobacterium tuberculosis,poses a considerable challenge to global public health.There are approximately 10 million new TB cases worldwide annually,and...Tuberculosis(TB),one of the oldest infectious diseases caused by Mycobacterium tuberculosis,poses a considerable challenge to global public health.There are approximately 10 million new TB cases worldwide annually,and TB claims the lives of nearly 3 million people each year,making it one of the leading causes of death from a single infectious disease[1].China ranks third globally in terms of TB burden,with approximately 733,000 TB cases reported in 2023[2].Based on the ecological model of health determinants developed by Whitehead and Dahlgren,health determinants can be classified into direct causes.展开更多
Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regula...Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regularity of continuous heavy precipitation over Southern China(SC)from April to June in 1979-2020 was systematically analyzed.The interaction between specific humidity and circulation field at the background-scale,the intra-seasonal-scale and the synoptic-scale,and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed.The results are as follows.Persistent heavy rainfall events(PHREs)over the SC during the April-June rainy season occur frequently from mid-May to mid-and late-June,exhibiting significant intra-seasonal oscillation(10-30-day)features.Vertically integrated moisture flux convergence(VIMFC)can well represent the variation of the PHREs.A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor(greater than 30 days),intraseasonal circulation disturbance(10-30-day)and background circulation(greater than 30 days),and water vapor convergences are the main factor.The SC is under the control of a warm and humid background and a strong intraseasonal cyclonic circulation,with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs.Meanwhile,the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days,eventually leading to the occurrence,development and persistence of heavy precipitation.展开更多
Through analysis of the results of a verified high-fidelity numerical model, the intra-seasonal variations(ISVs) in the depth of the 22°C isotherm(D22) in the South China Sea(SCS) basin are investigated. The resu...Through analysis of the results of a verified high-fidelity numerical model, the intra-seasonal variations(ISVs) in the depth of the 22°C isotherm(D22) in the South China Sea(SCS) basin are investigated. The results show that the ISVs in the D22 exhibit distinct seasonality in the SCS. The ISVs in the D22 are quite significant, especially within a band along the northwestern boundary of the basin and at the southern end of the basin during boreal winter. In these areas, the ratio of the standard deviations(STDs) of intra-seasonal band to the STDs of total data could exceed 0.6. Although the ISVs in the D22 are detectable in the area affected by the Vietnam Offshore Current during boreal summer and autumn, these variations are sometimes overwhelmed by oscillations with other frequencies. An analysis of the causes of the ISVs in the D22 in the SCS indicates that sea surface fluxes and wind stirring are not the dominant external driving mechanisms of the phenomena described above. The ISVs in the D22 are thought to be induced mainly by the thermodynamic adjustment of the ocean itself and the associated instabilities. The energy of the northern and southern bands that display strong ISVs in the D22 may be derived from eddy kinetic energy, rather than eddy available potential energy. The diversity of the propagation of the ISVs in the D22 is very conspicuous within these two bands.展开更多
Based on the daily maximum air temperature(T_(max))data from the China Meteorological Data Network and the NCEP/DOE reanalysis data,the intra-seasonal circulation and evolution of an extreme high temperature event(EHT...Based on the daily maximum air temperature(T_(max))data from the China Meteorological Data Network and the NCEP/DOE reanalysis data,the intra-seasonal circulation and evolution of an extreme high temperature event(EHTE)in the middle reaches of the Yangtze River(MYR)from August 9-21,2011 were explored,as well as the influence of diabatic heating on the position variation of the Western Pacific subtropical high(WPSH).Results show that the daily T_(max) in the MYR exhibits a vigorous intraseasonal oscillation(ISO)of 10-25 days in the extended summer of 1980-2018.The main factors affecting the EHTE in the summer of 2011 are the low-frequency wave train propagating southeastward in the mid-latitude of the upper troposphere and the low-frequency anticyclone moving northwestward in the lowlatitude of the mid-lower troposphere.The diagnosis of 925hPa thermodynamic equation indicates that the ISO features of the T_(max) in the core region is determined by the intra-seasonal variation of the adiabatic variation.In addition,the variations of the WPSH correspond well to the distribution of apparent heat source.In the early stage of the high temperature process,the apparent heat source in the north of the Bay of Bengal is a certain indicator for the westward extension of the WPSH.展开更多
Plants play an essential role in matter and energy transformations and are key messengers in the carbon and energy cycle. Net primary productivity (NPP) reflects the capability of plants to transform solar energy into...Plants play an essential role in matter and energy transformations and are key messengers in the carbon and energy cycle. Net primary productivity (NPP) reflects the capability of plants to transform solar energy into photosynthesis. It is very sensible for factors affecting on vegetation variability such as climate, soils, plant characteristics and human activities. So, it can be used as an indicator of actual and potential trend of vegetation. In this study we used the actual NPP which was derived from MODIS to assess the response of NPP to climate variables in Gadarif State, from 2000 to 2010. The correlations between NPP and climate variables (temperature and precipitation) are calculated using Pearson’s Correlation Coefficient and ordinary least squares regression. The main results show the following 1) the correlation Coefficient between NPP and mean annual temperature is Somewhat negative for Feshaga, Rahd, Gadarif and Galabat areas and weakly negative in Faw area;2) the correlation Coefficient between NPP and annual total precipitation is weakly negative in Faw, Rahd and Galabat areas and somewhat negative in Galabat and Rahd areas. This study demonstrated that the correlation analysis between NPP and climate variables (precipitation and temperature) gives reliably result of NPP responses to climate variables that is clearly in a very large scale of study area.展开更多
Rainfall is a key climate parameter that affects most operations that affect human life, especially in the tropics. Therefore, understanding the various factors that affect the distribution and intensity of this rainf...Rainfall is a key climate parameter that affects most operations that affect human life, especially in the tropics. Therefore, understanding the various factors that affect the distribution and intensity of this rainfall is important for effective planning among the different stakeholders in the weather and climate sectors. This study aimed at understanding how intra seasonal rainfall characteristics, especially Consecutive Dry Days (CDD) and Consecutive Wet Days (CWD), in the two major rainfall seasons will change under two future climate scenarios of RCP4.5 and RCP8.5 in Uganda, covering two future periods of 2021-2050 and 2051-2080. The results indicate a high likelihood of reduced consecutive rainfall days, especially over the Northeastern regions of the country, for both 2021-2050 and 2051-2080. However, the trends in the entire country for the two major rainfall seasons, March to May and September to November, are not significant. Nonetheless, the distribution of these days is important for most agricultural activities during different stages of crop growth. The consecutive dry days show a fairly increasing trend in the eastern part of the country, particularly in the second season of September to November. An increase in consecutive dry days implies more frequent dry spells in the midst of the growing season, potentially affecting some crops during critical growth stages.展开更多
An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of t...An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.展开更多
In order to solve the problem of the variable coefficient ordinary differen-tial equation on the bounded domain,the Lagrange interpolation method is used to approximate the exact solution of the equation,and the error...In order to solve the problem of the variable coefficient ordinary differen-tial equation on the bounded domain,the Lagrange interpolation method is used to approximate the exact solution of the equation,and the error between the numerical solution and the exact solution is obtained,and then compared with the error formed by the difference method,it is concluded that the Lagrange interpolation method is more effective in solving the variable coefficient ordinary differential equation.展开更多
As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice E...As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice Extent(SIE).The stage from 1979 to 2006 is characterized by high-frequency(i.e.,seasonal to interannual)temporal variability in SIE and zonal asymmetry in Sea Ice Concentration(SIC),which is primarily under the control of the Amundsen Sea Low(ASL).After 2007,however,sea ice changes exhibit a more spatially homogeneous pattern in SIC and a more temporally long-lasting mode in SIE.Further analysis reveals that sea ice-ocean interaction plays a major role in the low-frequency(i.e.,multiannual)variability of Antarctic sea ice from 2007−22.The related physical process is inferred to manifest as a strong coupling between the surface and the subsurface ocean layers,involving enhanced vertical convection and the downward delivery of the surface anomalies related to ice melting and freezing processes,thus maintaining the SIE anomalies for a longer time.Furthermore,this process mainly occurs in the Amundsen-Bellingshausen Sea(ABS)sector,and the weakened subsurface ocean stratification is the key factor triggering the coupling process in this region.We find that the Circumpolar Deep Water(CDW)over the ABS sector continued to shoal before 2007 and remained stable thereafter.It is speculated that the shoaling of the CDW may be a possible driver leading to the weakening of the subsurface stratification.展开更多
基金The Fund of China Ocean Mineral Resources R&D Association under contract No.DY135-E2-5-01the National Program on Global Change and Air-Sea InteractionⅡunder contract No.GASI-04-WLHY-01。
文摘In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific,is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products.Mooring observations were conducted from September 13,2017 to August 15,2018 in the COMRA contact area(10°N,154°W).The results were as follows:(1)At depths below 200 m,the kinetic energy of intra-seasonal variability(20-100 d)accounts for more than 40%of the overall low-frequency variability,while the ratio reaches more than 50%below 2000 m.(2)At depths below 200 m,currents show a synchronous oscillation with a characteristic time scale of 30 d,lasting from October to the following January;the energy of the 30-d oscillation increases with depth until the layer of approximately 4616 m,and the maximum velocity is approximately 10 cm/s.(3)The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.
文摘Climate change has led human beings to take an interest in the study of meteorological and climatic phenomena. In fact, the main impact of climate change on different sectors of society is caused by extreme events since the occurrence of extreme events leads to more impact related to change in mean climate. Unfortunately, the West African region is vulnerable to extreme rainfall impact because its economy is based on rain-fed agriculture. This study examined the seasonal variability of extreme rainfall in West Africa. Eight (8) climate indices were chosen from among the 27 defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). The nonparametric Mann-Kendall test was used to assess the seasonal trends. The indices of the same types (frequency or intensity) were compared to assess the intra-seasonal variation of extreme precipitation. The results indicate that, regardless of the season, the Gulf of Guinea receives more rainfall than the Sahel. This phenomenon is due to the fact that the coastal part of West Africa is under the influence of evaporation which is observed at the Atlantic Ocean and during the monsoon, while the other part is dominated by the desert. Mann-Kendall’s test revealed upward and downward trends during each season. The increase in extreme rainfall trends in the number of consecutive dry days suggests that droughts, due to global warming, could be observed and could have severe consequences in terms of water availability, energy supply, agricultural yields and ecosystems in West Africa. In addition, it can lead to the loss of biodiversity and health issues. It is therefore essential for policymakers or decisions makers to determine strategies and mitigation measures against climate change and its impacts on populations.
文摘The study of temporal and spatial distribution of ozone is very important for understanding the atmospheric chemistry and thereby its impact on environment, weather and climate. The intra-seasonal variability plays a major role in the inter-annual variability of weather parameters such as rainfall, temperature, pressure and atmospheric trace gas constituents such as atmospheric ozone. The strength of monsoon circulation and deep convection greatly modifies the atmospheric compositions and meteorological parameters such as rainfall amount, distributions of atmospheric trace gas concentrations and other weather parameters over the summer monsoon region. The daily total column ozone (TCO) measured over maritime station (Lakshadweep Island— 10°10'N & 73°30'E) and coastal station (Cochin—9°55'N and 76°16'E) using Microtop II Ozonometer were considered for the comparative study of seasonal and intra-seasonal variability for the year 2015. The annual average of total column ozone over Lakshadweep Islands and Cochin was 290 DU and 280 DU respectively for the year 2015. The greater concentrations in daily TCO measurements over Lakshadweep Islands for all seasons compared to Cochin lead to the speculations that, the surface ozone concentration is more because of pollution from the diesel burning emissions, since the whole Island’s population completely depends on diesel generator for the power supply. During winter season maritime station shows a decrease of ~30 DU in TCO over Lak-shadweep Island compared to coastal station Cochin (~18 DU) from the annual mean in the month of December. During pre-monsoon season TCO concentration is high over both locations. There is gradual increase of TCO concentration over Cochin from pre-monsoon to monsoon season and peak in the month of September, but decreasing TCO concentrations measured over Lakshadweep during July to August. In the analysis it was found that Intra-Seasonal Variability (ISV) in total column ozone over Lakshadweep Islands and Cochin during summer monsoon season was modulated by the monsoon dynamics and convection, thereby changes in the photochemistry of ozone production and distributions over the monsoon region. Two significant intra-seasonal oscillations (ISOs) such as Madden Julian Oscillation (MJO) and Quasi-Biweekly Oscillations (QBW) were identified in the TCO during monsoon season. The MJO shows higher periodicity (~54 days) over Lakshadweep Islands compared to the coastal station, Cochin (~48 days). Intra-seasonal variability of TCO over the maritime and coastal stations varies with geographic locations, marine boundary layer characteristics and also with seasons. The intra-seasonal variability or ISOs controls the interannual variability of TCO over a region. Hence deeper knowledge of ISOs in trace gases such as ozone helps us to understand more about the regional climate and air quality.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(42105015)+3 种基金Guangdong Basic and Applied Basic Research Foundation(2022A1515010659)Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2023SP209)Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(311021001)Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies(2020B1212060025)。
文摘Sub-seasonal prediction of regional compound heatwaves and their predictability sources remain unclear.In this study,the underlying mechanisms for the long-lasting compound heatwave over Southern China during July 1–18,2010,and the major sources of its sub-seasonal prediction skill are identified.The results show that both the development and decay of this compound heatwave are mainly dominated by atmospheric processes(i.e.,adiabatic heating associated with anticyclonic circulation),whereas land-atmosphere coupling processes play an important role in sustaining the heatwave.A further analysis indicates that by inducing anomalous anticyclonic circulations over Southern China,the tropical intraseasonal oscillations with periods of 30–60 days and 10–30 days facilitate the occurrence and maintenance of the heatwave during its entire and second half periods,respectively.The NCEP Climate Forecast System Version 2 shows a low skill in predicting the 2010 compound heatwave over Southern China when the lead time is longer than 2 pentads,which is largely attributed to the model’s bias in representing the intensity and phase of intra-seasonal oscillations.
文摘In this paper,we establish some strong laws of large numbers,which are for nonindependent random variables under the framework of sublinear expectations.One of our main results is for blockwise m-dependent random variables,and another is for sub-orthogonal random variables.Both extend the strong law of large numbers for independent random variables under sublinear expectations to the non-independent case.
基金Supported by NSFC(No.12101482)the Natural Science Foundation of Shaanxi Province,China(No.2018JQ1052)。
文摘In this paper,we consider the fourth-order parabolic equation with p(x)Laplacian and variable exponent source ut+∆^(2)u−div(|■u|^(p(x)−2■u))=|u|^(q(x))−1u.By applying potential well method,we obtain global existence,asymptotic behavior and blow-up of solutions with initial energy J(u_(0))≤d.Moreover,we estimate the upper bound of the blow-up time for J(u_(0))≤0.
基金funded by the Science and Technology Program of Gansu Province(25JRRA487)the National Natural Science Foundation of China(42101072)the Key Research and Development Program of Gansu Province(22YF7FA029).
文摘Tree growth variability is a key determinant of forest stabilities.Previous studies have shown that recent climate change has increased variability in tree growth,while others have challenged this viewpoint,leading to ongoing debate in this field.Moreover,gaps remain in understanding the climatic mechanisms driving increased tree growth variability,particularly for species simultaneously limited by multiple climate factors.In this study,we assessed the temporal trends in variability of Picea purpurea radial growth and its linkage with growth-climate sensitivity utilizing dendrochronological methods.Our results revealed a significant increase in P.purpurea radial growth variability from 1960 to 2020,as indicated by continuous rises in the standard deviation,coefficient of variation,and mean sensitivity of tree-ring width indices.The increased frequency of extreme growth declines further supported this finding.Furthermore,moisture condition in July was identified as a key limiting factor of P.purpurea growth.Notably,the strengthening relationship between tree-ring width indices and vapor pressure deficit(VPD)suggests that the moisture sensitivity for P.purpurea growth has increased over the period 1960-2020.This enhanced sensitivity to VPD,whose interannual variability has also increased synchronously,may have contributed to the rise in P.purpurea growth variability.Additionally,the maximum temperature in May was positively correlated with P.purpurea growth;however,there is little evidence that this factor contributed to the observed increase in growth variability.These findings provide new insights into P.purpurea growth trends and improve our understanding of the potential future impacts of climate change on forest ecosystems.
基金Supported by Natural Science Foundation General Project of Heilongjiang Province(C2018050).
文摘As a vital food crop,rice is an important part of global food crops.Studying the spatiotemporal changes in rice cultivation facilitates early prediction of production risks and provides support for agricultural policy decisions related to rice.With the increasing application of satellite remote sensing technology in crop monitoring,remote sensing for rice cultivation has emerged as a novel approach,offering new perspectives for monitoring rice planting.This paper briefly outlined the current research and development status of satellite remote sensing for monitoring rice cultivation both at home and abroad.Foreign scholars have made innovations in data sources and methodologies for satellite remote sensing monitoring,and utilized multi-source satellite information and machine learning algorithms to enhance the accuracy of rice planting monitoring.Scholars in China have achieved significant results in the study of satellite remote sensing for monitoring rice cultivation.Their research and application in monitoring rice planting areas provide valuable references for agricultural production management.However,satellite remote sensing monitoring of rice still faces challenges such as low spatiotemporal resolution and difficulties related to cloud cover and data fusion,which require further in-depth investigation.Additionally,there are shortcomings in the accuracy of remote sensing monitoring for fragmented farmland plots and smallholder farming.To address these issues,future efforts should focus on developing multi-source heterogeneous data fusion analysis technologies and researching monitoring systems.These advancements are expected to enable high-precision large-scale acquisition of rice planting information,laying a foundation for future smart agriculture.
基金funded by the National Natural Science Foundation of China(Nos.52209130 and 52379100)Shandong Provincial Natural Science Foundation(No.ZR2024ME112).
文摘Thermal-mechanical damage and deformation at the interface between shotcrete linings and the surrounding rock of tunnels under high-temperature and variable-temperature conditions are critical to the safe construction and operation of tunnel engineering.This study investigated the thermo-mechanical damage behavior of the composite interface between alkali-resistant glass fiber-reinforced concrete(ARGFRC)and granite,focusing on a plateau railway tunnel.Laboratory triaxial tests,laser scanning,XRD analysis,numerical simulations,and theoretical analyses were employed to investigate how different initial curing temperatures and joint roughness coefficient(JRC)influence interfacial damage behavior.The results indicate that an increase in interface roughness exacerbates the structural damage at the interface.At a JRC of 19.9 and a temperature of 70℃,crack initiation in granite was notably restrained when the confining pressure rose from 7 MPa to 10 MPa.Roughness-induced stress distribution at the interface was notably altered,although this effect became less pronounced under high confining pressure conditions.Additionally,during high-temperature curing,thermal stress concentration at the tips of micro-convex protrusions on the granite surface induced microcracks in the adjacent ARGFRC matrix,followed by deformation.These findings provide practical guidelines for designing concrete support systems to ensure tunnel structural safety in high-altitude regions with harsh thermal environments.
基金supported by the National Key Research and Development Program Project(2023YFC3107804)Planning Fund Project of Humanities and Social Sciences Research of the Ministry of Education(24YJA880097)the Graduate Education Reform Project in North China University of Technology(217051360025XN095-17)。
文摘Marine forecasting is critical for navigation safety and disaster prevention.However,traditional ocean numerical forecasting models are often limited by substantial errors and inadequate capture of temporal-spatial features.To address the limitations,the paper proposes a TimeXer-based numerical forecast correction model optimized by an exogenous-variable attention mechanism.The model treats target forecast values as internal variables,and incorporates historical temporal-spatial data and seven-day numerical forecast results from traditional models as external variables based on the embedding strategy of TimeXer.Using a self-attention structure,the model captures correlations between exogenous variables and target sequences,explores intrinsic multi-dimensional relationships,and subsequently corrects endogenous variables with the mined exogenous features.The model’s performance is evaluated using metrics including MSE(Mean Squared Error),MAE(Mean Absolute Error),RMSE(Root Mean Square Error),MAPE(Mean Absolute Percentage Error),MSPE(Mean Square Percentage Error),and computational time,with TimeXer and PatchTST models serving as benchmarks.Experiment results show that the proposed model achieves lower errors and higher correction accuracy for both one-day and seven-day forecasts.
基金supported by Supported by the Scientific Research Foundation for High-Level Talents of Zhoukou Normal University(ZKNUC2024018).
文摘Energy shortage has become one of themost concerning issues in the world today,and improving energy utilization efficiency is a key area of research for experts and scholars worldwide.Small-diameter heat exchangers offer advantages such as reduced material usage,lower refrigerant charge,and compact structure.However,they also face challenges,including increased refrigerant pressure drop and smaller heat transfer area inside the tubes.This paper combines the advantages and disadvantages of both small and large-diameter tubes and proposes a combined-diameter heat exchanger,consisting of large and small diameters,for use in the indoor units of split-type air conditioners.There are relatively few studies in this area.In this paper,A theoretical and numerical computation method is employed to establish a theoretical-numerical calculation model,and its reliability is verified through experiments.Using this model,the optimal combined diameters and flow path design for a combined-diameter heat exchanger using R32 as the working fluid are derived.The results show that the heat transfer performance of all combined diameter configurations improves by 2.79%to 8.26%compared to the baseline design,with the coefficient of performance(COP)increasing from 4.15 to 4.27~4.5.These designs can save copper material,but at the cost of an increase in pressure drop by 66.86%to 131.84%.The scheme IIIH,using R32,is the optimal combined-diameter and flow path configuration that balances both heat transfer performance and economic cost.
基金supported by the National Natural Science Foundation of China(82574173,82003516)Jiangsu Provincial Natural Science Foundation(BK20251958)+2 种基金Jiangsu Provincial Medical Key Discipline(ZDXK202250)Top Talent Awards Project Fund(RDF-TP-0023,RDF-TP-0030)Postgraduate Research Fund(PGRS2112022)at Xi'an Jiaotong-Liverpool University.
文摘Tuberculosis(TB),one of the oldest infectious diseases caused by Mycobacterium tuberculosis,poses a considerable challenge to global public health.There are approximately 10 million new TB cases worldwide annually,and TB claims the lives of nearly 3 million people each year,making it one of the leading causes of death from a single infectious disease[1].China ranks third globally in terms of TB burden,with approximately 733,000 TB cases reported in 2023[2].Based on the ecological model of health determinants developed by Whitehead and Dahlgren,health determinants can be classified into direct causes.
基金National Natural Science Foundation of China(42088101)。
文摘Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regularity of continuous heavy precipitation over Southern China(SC)from April to June in 1979-2020 was systematically analyzed.The interaction between specific humidity and circulation field at the background-scale,the intra-seasonal-scale and the synoptic-scale,and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed.The results are as follows.Persistent heavy rainfall events(PHREs)over the SC during the April-June rainy season occur frequently from mid-May to mid-and late-June,exhibiting significant intra-seasonal oscillation(10-30-day)features.Vertically integrated moisture flux convergence(VIMFC)can well represent the variation of the PHREs.A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor(greater than 30 days),intraseasonal circulation disturbance(10-30-day)and background circulation(greater than 30 days),and water vapor convergences are the main factor.The SC is under the control of a warm and humid background and a strong intraseasonal cyclonic circulation,with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs.Meanwhile,the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days,eventually leading to the occurrence,development and persistence of heavy precipitation.
基金The National Natural Science Foundation of China under contract No.41506037the Basic Scientific Fund for the National Public Research Institutes of China under contract No.2017Q06+1 种基金the Natural Science Foundation of Shandong Province,China under contract No.ZR2015PD009the NSFC-Shandong Joint Fund for Marine Science Research Centers under contract No.U1606405
文摘Through analysis of the results of a verified high-fidelity numerical model, the intra-seasonal variations(ISVs) in the depth of the 22°C isotherm(D22) in the South China Sea(SCS) basin are investigated. The results show that the ISVs in the D22 exhibit distinct seasonality in the SCS. The ISVs in the D22 are quite significant, especially within a band along the northwestern boundary of the basin and at the southern end of the basin during boreal winter. In these areas, the ratio of the standard deviations(STDs) of intra-seasonal band to the STDs of total data could exceed 0.6. Although the ISVs in the D22 are detectable in the area affected by the Vietnam Offshore Current during boreal summer and autumn, these variations are sometimes overwhelmed by oscillations with other frequencies. An analysis of the causes of the ISVs in the D22 in the SCS indicates that sea surface fluxes and wind stirring are not the dominant external driving mechanisms of the phenomena described above. The ISVs in the D22 are thought to be induced mainly by the thermodynamic adjustment of the ocean itself and the associated instabilities. The energy of the northern and southern bands that display strong ISVs in the D22 may be derived from eddy kinetic energy, rather than eddy available potential energy. The diversity of the propagation of the ISVs in the D22 is very conspicuous within these two bands.
基金National Key Research and Development Program of China(2018YFC1505804)National Natural Science Foundation of China(42075032)。
文摘Based on the daily maximum air temperature(T_(max))data from the China Meteorological Data Network and the NCEP/DOE reanalysis data,the intra-seasonal circulation and evolution of an extreme high temperature event(EHTE)in the middle reaches of the Yangtze River(MYR)from August 9-21,2011 were explored,as well as the influence of diabatic heating on the position variation of the Western Pacific subtropical high(WPSH).Results show that the daily T_(max) in the MYR exhibits a vigorous intraseasonal oscillation(ISO)of 10-25 days in the extended summer of 1980-2018.The main factors affecting the EHTE in the summer of 2011 are the low-frequency wave train propagating southeastward in the mid-latitude of the upper troposphere and the low-frequency anticyclone moving northwestward in the lowlatitude of the mid-lower troposphere.The diagnosis of 925hPa thermodynamic equation indicates that the ISO features of the T_(max) in the core region is determined by the intra-seasonal variation of the adiabatic variation.In addition,the variations of the WPSH correspond well to the distribution of apparent heat source.In the early stage of the high temperature process,the apparent heat source in the north of the Bay of Bengal is a certain indicator for the westward extension of the WPSH.
文摘Plants play an essential role in matter and energy transformations and are key messengers in the carbon and energy cycle. Net primary productivity (NPP) reflects the capability of plants to transform solar energy into photosynthesis. It is very sensible for factors affecting on vegetation variability such as climate, soils, plant characteristics and human activities. So, it can be used as an indicator of actual and potential trend of vegetation. In this study we used the actual NPP which was derived from MODIS to assess the response of NPP to climate variables in Gadarif State, from 2000 to 2010. The correlations between NPP and climate variables (temperature and precipitation) are calculated using Pearson’s Correlation Coefficient and ordinary least squares regression. The main results show the following 1) the correlation Coefficient between NPP and mean annual temperature is Somewhat negative for Feshaga, Rahd, Gadarif and Galabat areas and weakly negative in Faw area;2) the correlation Coefficient between NPP and annual total precipitation is weakly negative in Faw, Rahd and Galabat areas and somewhat negative in Galabat and Rahd areas. This study demonstrated that the correlation analysis between NPP and climate variables (precipitation and temperature) gives reliably result of NPP responses to climate variables that is clearly in a very large scale of study area.
文摘Rainfall is a key climate parameter that affects most operations that affect human life, especially in the tropics. Therefore, understanding the various factors that affect the distribution and intensity of this rainfall is important for effective planning among the different stakeholders in the weather and climate sectors. This study aimed at understanding how intra seasonal rainfall characteristics, especially Consecutive Dry Days (CDD) and Consecutive Wet Days (CWD), in the two major rainfall seasons will change under two future climate scenarios of RCP4.5 and RCP8.5 in Uganda, covering two future periods of 2021-2050 and 2051-2080. The results indicate a high likelihood of reduced consecutive rainfall days, especially over the Northeastern regions of the country, for both 2021-2050 and 2051-2080. However, the trends in the entire country for the two major rainfall seasons, March to May and September to November, are not significant. Nonetheless, the distribution of these days is important for most agricultural activities during different stages of crop growth. The consecutive dry days show a fairly increasing trend in the eastern part of the country, particularly in the second season of September to November. An increase in consecutive dry days implies more frequent dry spells in the midst of the growing season, potentially affecting some crops during critical growth stages.
基金supported by the National Natural Science Foundation of China(No.51905123)Major Scientific and Technological Innovation Program of Shandong Province,China(Nos.2020CXGC010303,2022ZLGX04)Key R&D Programme of Shandong Province,China(No.2022JMRH0308).
文摘An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.
文摘In order to solve the problem of the variable coefficient ordinary differen-tial equation on the bounded domain,the Lagrange interpolation method is used to approximate the exact solution of the equation,and the error between the numerical solution and the exact solution is obtained,and then compared with the error formed by the difference method,it is concluded that the Lagrange interpolation method is more effective in solving the variable coefficient ordinary differential equation.
基金supported by the National Natural Science Foundation China(Grant No.42176222).
文摘As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice Extent(SIE).The stage from 1979 to 2006 is characterized by high-frequency(i.e.,seasonal to interannual)temporal variability in SIE and zonal asymmetry in Sea Ice Concentration(SIC),which is primarily under the control of the Amundsen Sea Low(ASL).After 2007,however,sea ice changes exhibit a more spatially homogeneous pattern in SIC and a more temporally long-lasting mode in SIE.Further analysis reveals that sea ice-ocean interaction plays a major role in the low-frequency(i.e.,multiannual)variability of Antarctic sea ice from 2007−22.The related physical process is inferred to manifest as a strong coupling between the surface and the subsurface ocean layers,involving enhanced vertical convection and the downward delivery of the surface anomalies related to ice melting and freezing processes,thus maintaining the SIE anomalies for a longer time.Furthermore,this process mainly occurs in the Amundsen-Bellingshausen Sea(ABS)sector,and the weakened subsurface ocean stratification is the key factor triggering the coupling process in this region.We find that the Circumpolar Deep Water(CDW)over the ABS sector continued to shoal before 2007 and remained stable thereafter.It is speculated that the shoaling of the CDW may be a possible driver leading to the weakening of the subsurface stratification.
