Recent studies have suggested that rapid warming over the Mongolian Plateau(MP) may intensify extreme heat events(EHEs). However, the characteristics and mechanisms driving summer EHEs over the MP(MP-EHEs) remain uncl...Recent studies have suggested that rapid warming over the Mongolian Plateau(MP) may intensify extreme heat events(EHEs). However, the characteristics and mechanisms driving summer EHEs over the MP(MP-EHEs) remain unclear. This study explores the interannual variations in summer MP-EHEs and their relationship with the summer soil moisture over the Inner Tibetan Plateau(TP-SM). The results reveal that changes in the MP-EHEs are linked to descending atmospheric motion induced by a local high-pressure system over the MP region. Descending motion further results in decreased mid-tolow-level cloud cover and increased shortwave radiation, thereby warming the surface and triggering summer MP-EHEs.Further analysis indicates that increased TP-SM results in a greater latent heat flux, triggering a local secondary circulation that reinforces the local high-pressure system over the MP region, thus serving to promote the occurrence of summer MPEHEs. Additionally, model results from the linear baroclinic model(LBM) and CMIP6 further confirm that variations in summer TP-SM contribute to the occurrence of the MP-EHEs.展开更多
In aerospace,nuclear power,and new energy vehicles industries,utilizing integrated metal components with extreme sizes and/or structures is crucial for achieving significant weight-saving,performance-improvement,and e...In aerospace,nuclear power,and new energy vehicles industries,utilizing integrated metal components with extreme sizes and/or structures is crucial for achieving significant weight-saving,performance-improvement,and excellent reliability.These components,made from metal sheets,rings,or tubes,exhibit characteristics like ultra-thin,ultra-thick,ultra-large,ultra-long,ultra-high ribs,and large variable diameters.During plastic de-formation in metal forming processes,defects such as ruptures,wrinkles,excessive strain differences,and un-expected weak performance areas are likely to occur due to the intersection of multiple effects in different research disciplines,including materials science,processes,and mechanics of materials.Consequently,the smooth forming of integrated parts is difficult.It is the first time to review,summarize,and analyze the ad-vancement of forming methods for producing integrated parts with extreme sizes and structures.The general academic ideas to change the process conditions and sequences to optimize stress state and improve plastic deformation ability for forming the components with extreme sizes/structures are introduced.Practical ex-amples,discussed in detail in the paper,include the forming of(i)integrated ultra-thin and ultra-thick sheet components;(ii)integrated ultra-large size ring components with thin wall and high ribs;and(iii)integrated ultra-long tube components with large perimeter difference.Various plasticity technologies and process se-quences have been developed.The key processes and applications of the technologies are discussed in detail,which achieve successful plastic forming of integrated components.This paper provides state-of-the-art and perspectives for the rapidly advancing material forming fields of key metal components for the next generation of equipment.展开更多
Amphibious vehicles are more prone to attitude instability compared to ships,making it crucial to develop effective methods for monitoring instability risks.However,large inclination events,which can lead to instabili...Amphibious vehicles are more prone to attitude instability compared to ships,making it crucial to develop effective methods for monitoring instability risks.However,large inclination events,which can lead to instability,occur frequently in both experimental and operational data.This infrequency causes events to be overlooked by existing prediction models,which lack the precision to accurately predict inclination attitudes in amphibious vehicles.To address this gap in predicting attitudes near extreme inclination points,this study introduces a novel loss function,termed generalized extreme value loss.Subsequently,a deep learning model for improved waterborne attitude prediction,termed iInformer,was developed using a Transformer-based approach.During the embedding phase,a text prototype is created based on the vehicle’s operation log data is constructed to help the model better understand the vehicle’s operating environment.Data segmentation techniques are used to highlight local data variation features.Furthermore,to mitigate issues related to poor convergence and slow training speeds caused by the extreme value loss function,a teacher forcing mechanism is integrated into the model,enhancing its convergence capabilities.Experimental results validate the effectiveness of the proposed method,demonstrating its ability to handle data imbalance challenges.Specifically,the model achieves over a 60%improvement in root mean square error under extreme value conditions,with significant improvements observed across additional metrics.展开更多
Ensuring reliable power supply in urban distribution networks is a complex and critical task.To address the increased demand during extreme scenarios,this paper proposes an optimal dispatch strategy that considers the...Ensuring reliable power supply in urban distribution networks is a complex and critical task.To address the increased demand during extreme scenarios,this paper proposes an optimal dispatch strategy that considers the coordination with virtual power plants(VPPs).The proposed strategy improves systemflexibility and responsiveness by optimizing the power adjustment of flexible resources.In the proposed strategy,theGaussian Process Regression(GPR)is firstly employed to determine the adjustable range of aggregated power within the VPP,facilitating an assessment of its potential contribution to power supply support.Then,an optimal dispatch model based on a leader-follower game is developed to maximize the benefits of the VPP and flexible resources while guaranteeing the power balance at the same time.To solve the proposed optimal dispatch model efficiently,the constraints of the problem are reformulated and resolved using the Karush-Kuhn-Tucker(KKT)optimality conditions and linear programming duality theorem.The effectiveness of the strategy is illustrated through a detailed case study.展开更多
Initial-dependent extreme multi-stability and offset-boosted coexisting attractors have been significantly concerned recently.This paper constructs a novel five-dimensional(5-D)two-memristor-based dynamical system by ...Initial-dependent extreme multi-stability and offset-boosted coexisting attractors have been significantly concerned recently.This paper constructs a novel five-dimensional(5-D)two-memristor-based dynamical system by introducing two memristors with cosine memductance into a three-dimensional(3-D)linear autonomous dissipative system.Through theoretical analyses and numerical plots,the memristor initial-boosted coexisting plane bifurcations are found and the memristor initial-dependent extreme multi-stability is revealed in such a two-memristor-based dynamical system with plane equilibrium.Furthermore,a dimensionality reduction model with the determined equilibrium is established via an integral transformation method,upon which the memristor initial-dependent extreme multi-stability is reconstituted theoretically and expounded numerically.Finally,physically circuit-implemented PSIM(power simulation)simulations are carried out to validate the plane offset-boosted coexisting behaviors.展开更多
We present a class of two-dimensional memristive maps with a cosine memristor. The memristive maps do not have any fixed points, so they belong to the category of nonlinear maps with hidden attractors. The rich dynami...We present a class of two-dimensional memristive maps with a cosine memristor. The memristive maps do not have any fixed points, so they belong to the category of nonlinear maps with hidden attractors. The rich dynamical behaviors of these maps are studied and investigated using different numerical tools, including phase portrait, basins of attraction,bifurcation diagram, and Lyapunov exponents. The two-parameter bifurcation analysis of the memristive map is carried out to reveal the bifurcation mechanism of its dynamical behaviors. Based on our extensive simulation studies, the proposed memristive maps can produce hidden periodic, chaotic, and hyper-chaotic attractors, exhibiting extremely hidden multistability, namely the coexistence of infinite hidden attractors, which was rarely observed in memristive maps. Potentially,this work can be used for some real applications in secure communication, such as data and image encryptions.展开更多
To meet the challenge of mismatches between power supply and demand,modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids.Furthermore,it is essential to understand the ...To meet the challenge of mismatches between power supply and demand,modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids.Furthermore,it is essential to understand the effectiveness of flexibility management strategies under different climate conditions and extreme weather events.Using both typical and extreme weather data from cities in five major climate zones of China,this study investigates the energy flexibility potential of an office building under three short-term HVAC management strategies in the context of different climates.The results show that the peak load flexibility and overall energy performance of the three short-term strategies were affected by the surrounding climate conditions.The peak load reduction rate of the pre-cooling and zone temperature reset strategies declined linearly as outdoor temperature increased.Under extreme climate conditions,the daily peak-load time was found to be over two hours earlier than under typical conditions,and the intensive solar radiation found in the extreme conditions can weaken the correlation between peak load reduction and outdoor temperature,risking the ability of a building’s HVAC system to maintain a comfortable indoor environment.展开更多
This past year, 2024, is on track to be the warmest year, joining 2023 as the two hottest years on record. With the exceptional heat, weather and climate extremes were common across the world. In particular, 2024 has ...This past year, 2024, is on track to be the warmest year, joining 2023 as the two hottest years on record. With the exceptional heat, weather and climate extremes were common across the world. In particular, 2024 has seen a remarkable run of extreme precipitation events and resulting impacts. Here, we provide an overview of the most notable extreme events of the year, including extreme precipitation and floods, tropical cyclones, and droughts. The characteristics and impacts of these extreme events are summarized, followed by discussion on the physical drivers and the role of global warming.Finally, we also discuss the future prospects in extreme event studies, including impact-based perspectives, challenges in attribution of precipitation extremes, and the existing gap to minimize impacts from climate extremes.展开更多
Located downstream the Kupang Catchment in Indonesia,Pekalongan faces significant land subsidence issues,leading to severe coastal flooding.This study aimed to assess the impact of climate change on future flow regime...Located downstream the Kupang Catchment in Indonesia,Pekalongan faces significant land subsidence issues,leading to severe coastal flooding.This study aimed to assess the impact of climate change on future flow regimes and hydrological extremes to inform long-term water resources management strategies for the Kupang Catchment.Utilizing precipitation and air temperature data from general circulation models in the Coupled Model Intercomparison Project 6(CMIP6)and employing bias correction techniques,the Soil and Water Assessment Tool(SWAT)hydrological model was employed to analyze climate-induced changes in hydrological fluxes,specifically streamflow.Results indicated a consistent increase in monthly streamflow during the wet season,with a substantial rise of 22.8%,alongside a slight decrease of 18.0%during the dry season.Moreover,both the frequency and severity of extremely low and high flows were projected to intensify by approximately 50%and 70%,respectively,for a 20-year return period,suggesting heightened flood and drought risks in the future.The observed declining trend in low flow,by up to 11%,indicated the potential for long-term groundwater depletion exacerbating the threat of land subsidence and coastal flooding,especially in areas with inadequate surface water management policies and infrastructure.展开更多
This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,t...This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,the maximum regionalaverage HRR and site-observed HRR,which exhibited sequential development over southern,middle,and northern key regions.These rainfall extremes occurred in an environment where a high-pressure barrier over North China prevented the intrusion of cold air masses from the north while a northward-moving typhoon remnant vortex and its associated low-level jet(LLJ)transported warm and moist airflow from the south.Two distinct echo evolution modes and convection initiation mechanisms are identified for the two types of extreme HRRs.The maximum regional-average HRR occurred when the LLJ arrived to the east of the key regions,while the maximum site-observed HRR occurred when the warmer vortex center influenced the regions.Taking the northern key region as a representation,at the time of the maximum regional-average HRR,slantwise ascent of the airflow along a warm-frontal-like boundary released energy related to symmetrical instability,resulting in stratiform rainfall with weak convective cores.The transport of locally initiated convection over the eastern plain region,where the atmospheric stratification was more potentially unstable,also significantly contributed.When the maximum site-observed HRR occurred,the terrain lifting of warm and moist southeast airflow led to intense convection over the mountain foothills.Overall,the passage of the warm-core typhoon remnant vortex and interaction with Taihang Mountains determined the timing and location of extreme HRRs across the key regions.展开更多
In the context of global warming,it is anticipated that both the intensity and the frequency of future global extreme high precipitation(EHP)and extreme high temperature(EHT)events will increase.To evaluate the future...In the context of global warming,it is anticipated that both the intensity and the frequency of future global extreme high precipitation(EHP)and extreme high temperature(EHT)events will increase.To evaluate the future extreme climate changes in the Asian arid region and Tibetan Plateau,this study applied the NASA Earth Exchange Global Daily Downscaled Projections(NEX-GDDP-CMIP6)to assess the changes in EHP(Rx5d and R95pTOT)and EHT(TX90p and TXx)under different emission scenarios in the 21st century.Findings suggest that both the frequency and the intensity of the extreme indices will increase,exhibiting accelerated growth under higher emission scenarios,particularly under the SSP5-8.5 emission scenario.It is suggested that the growth of EHT and EHP in the early subperiod of the 21st century(2026-2045)will be relatively moderate,with small differences between different emission scenarios.However,by the middle subperiod of the 21st century(2041-2060),the differences between different emission scenarios will become larger than the 2035s and the growth will become more intense.In western central Asia,TX90p,TXx,Rx5d,and R95pTOT increase by 9.7%-14.2%(13.3%-24.7%),1.3℃-1.7℃(1.6℃-2.7℃),6.5%-8.9%(8.2%-8.8%),and 18.1%-27.0%(25.6%-30.0%)by the early(middle)subperiod;in eastern central Asia,TX90p,TXx,Rx5d,and R95pTOT increase 8.1%-12.0%(11.3%-21.1%),1.4℃-1.8℃(1.9℃-2.9℃),7.4%-9.7%(10.4%-13.8%),and 20.2%-29.3%(32.0%-40.8%)by the early(middle)subperiod;and over the Tibetan Plateau,TX90p,TXx,Rx5d,and R95pTOT increase 12.5%-17.4%(17.0%-31.0%),1.2℃-1.5℃(1.6℃-2.5℃),7.2%-10.0%(9.9%-15.0%),and 26.6%-33.1%(36.1%-55.3%)by the early(middle)subperiod.展开更多
1 EXTREME DROUGHT AND HYDROGEODESY TECHNOLOGIES The World Meteorological Organization has officially declared 2023 as the hottest year on record,with the average global temperature surpassing pre-industrial(1850-1900)...1 EXTREME DROUGHT AND HYDROGEODESY TECHNOLOGIES The World Meteorological Organization has officially declared 2023 as the hottest year on record,with the average global temperature surpassing pre-industrial(1850-1900)average by 1.45℃.While temperature is not the only climate observable from the complex processes for the geneses of droughts,recent hottest years have witnessed numerous instances of extreme droughts.展开更多
In recent years,there has been a pronounced increase in the frequency of extreme weather events.To compre hensively examine the impact of extreme weather on ecosystem services within the Wuhan Urban Agglomera tion(WUA...In recent years,there has been a pronounced increase in the frequency of extreme weather events.To compre hensively examine the impact of extreme weather on ecosystem services within the Wuhan Urban Agglomera tion(WUA),this study utilized meteorological station data,the Mann-Kendall(MK)test,and the Standardized Precipitation-Evapotranspiration Index(SPEI)to quantify the variation trends in heatwaves(HW)and droughts from 1961 to 2020.Then the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model was employed to evaluate and compare the differences in water yield and climate regulation ecosystem services un der various HW,droughts,and HW-drought combination scenarios.The results show that over the past 60 years,the temperature,duration,and frequency of HW have significantly increased in the WUA.Specifically,the high est HW temperature,total HW days,HW frequency,and average HW temperature showed changing trend of+0.17℃/decade,+1.4 day/decade,+0.19 event/decade,and+0.07℃/decade,respectively.The year 2000 was identified as a mutation year for HW,characterized by increased frequency and heightened severity thereafter.The SPEI value exhibited an insignificant upward trend,with 1980 marked as a mutation year,indicating a de creasing trend in drought occurrences after 1980.Heatwaves have a weakening effect on both water yield and climate regulation services,while drought significantly weakened water yield and had a relatively modest effect on climate regulation.During HW-drought composite period,the average monthly water yield showed a notable discrepancy of 60 mm compared to humid years.Besides,as heatwaves intensify,the area of low aggregation for ecosystem services expands,whereas the area of high aggregation decreases.This study provides a preliminary understanding of the impact of urban extreme weather on urban ecosystem services under changing climatic conditions.展开更多
Due to the high elevation and cold climate of the Tibetan Plateau,the western region retains extensive snow cover during the summer,which can exhibit rapid variability over the course of just a few days.This study uti...Due to the high elevation and cold climate of the Tibetan Plateau,the western region retains extensive snow cover during the summer,which can exhibit rapid variability over the course of just a few days.This study utilizes numerical experiments to investigate the atmospheric response to extreme Tibetan Plateau snow cover(TPSC)events on a subseasonal timescale during summer.The results indicate that the subseasonal variations in TPSC exert limited impact on nonlocal atmospheric circulation and temperature during this period.Nevertheless,local surface energy and atmospheric temperature exhibit rapid cooling responses to increased snow cover.Specifically,an increase in snow cover over the western Tibetan Plateau leads to a sharp rise in surface albedo,resulting in a reduction in land surface energy and a negative response in the diabatic heating rate from the surface to 350 hPa locally.This negative diabatic heating response subsequently causes a decline in both surface and overlying atmospheric temperatures.The temperature response is confined to the western Tibetan Plateau and extends vertically from the surface to approximately 350 hPa.These extreme TPSC events and their associated atmospheric impacts occur within a two-week timescale.展开更多
Precision actuation is a foundational technology in high-end equipment domains,where stroke,velocity,and accuracy are critical for processing and/or detection quality,precision in spacecraft flight trajectories,and ac...Precision actuation is a foundational technology in high-end equipment domains,where stroke,velocity,and accuracy are critical for processing and/or detection quality,precision in spacecraft flight trajectories,and accuracy in weapon system strikes.Piezoelectric actuators(PEAs),known for their nanometer-level precision,flexible stroke,resistance to electromagnetic interference,and scalable structure,have been widely adopted across various fields.Therefore,this study focuses on extreme scenarios involving ultra-high precision(micrometer and beyond),minuscule scales,and highly complex operational conditions.It provides a comprehensive overview of the types,working principles,advantages,and disadvantages of PEAs,along with their potential applications in piezo-actuated smart mechatronic systems(PSMSs).To address the demands of extreme scenarios in high-end equipment fields,we have identified five representative application areas:positioning and alignment,biomedical device configuration,advanced manufacturing and processing,vibration mitigation,micro robot system.Each area is further divided into specific subcategories,where we explore the underlying relationships,mechanisms,representative schemes,and characteristics.Finally,we discuss the challenges and future development trends related to PEAs and PSMSs.This work aims to showcase the latest advancements in the application of PEAs and provide valuable guidance for researchers in this field.展开更多
This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and stru...This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and structural response of the platform are studied,considering the actual platform motion and free surface rise under extreme sea states.First,the effects of the wave frequency and direction on the wave-induced loads and dynamic responses were examined.The motion at a wave direction angle of 0°is relatively low.On this basis,the angle constrained by the two sides of the Sharp Eagle floaters should be aligned with the main wave direction to avoid significant platform motion under extreme sea states.Additionally,the structural response of the platform,including the wave-absorbing floaters,is investigated.The results highlighted that the conditions or locations where yielding,buckling,and fatigue failures occur were different.In this context,the connection area of the Sharp Eagle floaters and platform is prone to yielding failure under oblique wave action,whereas the pontoon and side of the Sharp Eagle floaters are prone to buckling failure during significant vertical motion.Additionally,fatigue damage is most likely to occur at the connection between the middle column on both sides of the Sharp Eagle floaters and the pontoons.The findings of this paper revealed an intrinsic connection between wave-induced loads and the dynamic and structural responses of the platform,which provides a useful reference for the improved design of WECs.展开更多
The impact of extreme temperatures on the health of individuals in different organizations remains uncertain.We employed stratified analyses to examine the impacts of summer(April-September)daily maximum temperatures ...The impact of extreme temperatures on the health of individuals in different organizations remains uncertain.We employed stratified analyses to examine the impacts of summer(April-September)daily maximum temperatures and winter(October-March)daily minimum temperatures on blood pressure and lipid profiles across government staff,com-pany employees,and researchers.We examined 209,477 physical examination records from a physical examination center in the First Affiliated Hospital of USTC from 2017 to 2021.Employing a segmented regression model within the frame-work of generalized linear regression(GLM),we examined the causal impact of extreme temperatures on health outcomes.Additionally,sensitivity analyses were conducted via distributed lag nonlinear models(DLNMs),with a focus on ob-serving the long-term effects over a period of 21 days.Our findings indicate that government staff face increased health risks during extremely low temperatures,regardless of the season.Compared with participants experiencing median tem-peratures,government staff exposed to extremely low temperatures(below the 10th percentile,below 24℃)in the sum-mer presented maximum increases of 2.32 mmHg(95%CI:1.542-3.098)in diastolic blood pressure and 6.481 mmHg(95%CI:5.368-7.594)in systolic blood pressure.In winter,government staff exposed to temperatures below the 10th per-centile(below 1℃)demonstrated maximum increases of 0.278 mmol/L(95%CI:0.210-0.346)in total cholesterol,0.153 mmol/L(95%CI:0.032-0.274)in triglycerides,and 0.077 mmol/L(95%CI:0.192-0.134)in low-density lipoprotein.Conversely,warm winters benefit company employees,whereas researchers exhibit lower sensitivity to temperature changes in winter.The maximum temperatures in summer and minimum temperatures in winter had greater impacts on in-dividuals.Small temperature fluctuations impact health more than large changes do.Notably,both the maximum and min-imum temperatures were better predictors of health outcomes than the daily average temperature was.Blood pressure con-sistently displayed significant associations with temperature across all three groups,with extremely low temperatures in-creasing the risk and extremely high temperatures reducing it.However,the relationship between temperature and blood lipids is complex.展开更多
This study investigates trends in extreme precipitation events(EPEs)across Antarctica from 1979 to 2023,analyzing changes in EPE frequency,intensity,and the proportion of extreme to total precipitation.Using Self-Orga...This study investigates trends in extreme precipitation events(EPEs)across Antarctica from 1979 to 2023,analyzing changes in EPE frequency,intensity,and the proportion of extreme to total precipitation.Using Self-Organizing Map(SOM)techniques,the study distinguishes the contributions from thermodynamic,dynamic,and interaction components in explaining these trends.Positive EPE occurrence trends are observed across the Bellingshausen and Weddell Seas,Dronning Maud Land,and parts of the Southern Ocean,with declines limited to Queen Mary Land.Thermodynamic factors,responsible for 96.0%of the overall trend,are driven by increased water vapor content in polar air masses.Dynamic contributions,representing 10.8%,are linked to a strengthened Amundsen Sea Low(ASL)associated with the Southern Annular Mode(SAM)and Pacific South American(PSA)trends.Interaction effects make a slightly negative contribution(-6.8%)to the overall trend.Variations in water vapor transport and vertical velocity tied to annual 500-hPa geopotential height anomalies further explain EPE trends.These findings provide insight into the atmospheric processes that influence Antarctic EPEs,with implications for understanding the climatic impact on the polar environment.展开更多
A nonlinear multi-scale interaction(NMI)model was proposed and developed by the first author for nearly 30 years to represent the evolution of atmospheric blocking.In this review paper,we first review the creation and...A nonlinear multi-scale interaction(NMI)model was proposed and developed by the first author for nearly 30 years to represent the evolution of atmospheric blocking.In this review paper,we first review the creation and development of the NMI model and then emphasize that the NMI model represents a new tool for identifying the basic physics of how climate change influences mid-to-high latitude weather extremes.The building of the NMI model took place over three main periods.In the 1990s,a nonlinear Schr?dinger(NLS)equation model was presented to describe atmospheric blocking as a wave packet;however,it could not depict the lifetime(10-20 days)of atmospheric blocking.In the 2000s,we proposed an NMI model of atmospheric blocking in a uniform basic flow by making a scale-separation assumption and deriving an eddyforced NLS equation.This model succeeded in describing the life cycle of atmospheric blocking.In the 2020s,the NMI model was extended to include the impact of a changing climate mainly by altering the basic zonal winds and the magnitude of the meridional background potential vorticity gradient(PVy).Model results show that when PVy is smaller,blocking has a weaker dispersion and a stronger nonlinearity,so blocking can be more persistent and have a larger zonal scale and weaker eastward movement,thus favoring stronger weather extremes.However,when PVy is much smaller and below a critical threshold under much stronger winter Arctic warming of global warming,atmospheric blocking becomes locally less persistent and shows a much stronger westward movement,which acts to inhibit local cold extremes.Such a case does not happen in summer under global warming because PVy fails to fall below the critical threshold.Thus,our theory indicates that global warming can render summer-blocking anticyclones and mid-to-high latitude heatwaves more persistent,intense,and widespread.展开更多
It is important for regional water resources management to know the agricultural water consumption information several months in advance.Forecasting reference evapotranspiration(ET_(0))in the next few months is import...It is important for regional water resources management to know the agricultural water consumption information several months in advance.Forecasting reference evapotranspiration(ET_(0))in the next few months is important for irrigation and reservoir management.Studies on forecasting of multiple-month ahead ET_(0) using machine learning models have not been reported yet.Besides,machine learning models such as the XGBoost model has multiple parameters that need to be tuned,and traditional methods can get stuck in a regional optimal solution and fail to obtain a global optimal solution.This study investigated the performance of the hybrid extreme gradient boosting(XGBoost)model coupled with the Grey Wolf Optimizer(GWO)algorithm for forecasting multi-step ahead ET_(0)(1-3 months ahead),compared with three conventional machine learning models,i.e.,standalone XGBoost,multi-layer perceptron(MLP)and M5 model tree(M5)models in the subtropical zone of China.The results showed that theGWO-XGB model generally performed better than the other three machine learning models in forecasting 1-3 months ahead ET_(0),followed by the XGB,M5 and MLP models with very small differences among the three models.The GWO-XGB model performed best in autumn,while the MLP model performed slightly better than the other three models in summer.It is thus suggested to apply the MLP model for ET_(0) forecasting in summer but use the GWO-XGB model in other seasons.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.42288101)the Young Scientists Fund of the National Natural Science Foundation of China (Grand No.42505018)the Shanghai “Science and Technology Innovation Action Plan” Venus Project (Grant No.23YF1437300)。
文摘Recent studies have suggested that rapid warming over the Mongolian Plateau(MP) may intensify extreme heat events(EHEs). However, the characteristics and mechanisms driving summer EHEs over the MP(MP-EHEs) remain unclear. This study explores the interannual variations in summer MP-EHEs and their relationship with the summer soil moisture over the Inner Tibetan Plateau(TP-SM). The results reveal that changes in the MP-EHEs are linked to descending atmospheric motion induced by a local high-pressure system over the MP region. Descending motion further results in decreased mid-tolow-level cloud cover and increased shortwave radiation, thereby warming the surface and triggering summer MP-EHEs.Further analysis indicates that increased TP-SM results in a greater latent heat flux, triggering a local secondary circulation that reinforces the local high-pressure system over the MP region, thus serving to promote the occurrence of summer MPEHEs. Additionally, model results from the linear baroclinic model(LBM) and CMIP6 further confirm that variations in summer TP-SM contribute to the occurrence of the MP-EHEs.
基金Supported by National Natural Science Foundation of China(Grant Nos.52422510,52373320,52175360,50725517)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(Grant No.2021QNRC001)+1 种基金the Key R&D Program of Hubei Province(Grant No.2024BAB080)Natural Science Foundation of Wuhan(Grant No.2024040801020257).
文摘In aerospace,nuclear power,and new energy vehicles industries,utilizing integrated metal components with extreme sizes and/or structures is crucial for achieving significant weight-saving,performance-improvement,and excellent reliability.These components,made from metal sheets,rings,or tubes,exhibit characteristics like ultra-thin,ultra-thick,ultra-large,ultra-long,ultra-high ribs,and large variable diameters.During plastic de-formation in metal forming processes,defects such as ruptures,wrinkles,excessive strain differences,and un-expected weak performance areas are likely to occur due to the intersection of multiple effects in different research disciplines,including materials science,processes,and mechanics of materials.Consequently,the smooth forming of integrated parts is difficult.It is the first time to review,summarize,and analyze the ad-vancement of forming methods for producing integrated parts with extreme sizes and structures.The general academic ideas to change the process conditions and sequences to optimize stress state and improve plastic deformation ability for forming the components with extreme sizes/structures are introduced.Practical ex-amples,discussed in detail in the paper,include the forming of(i)integrated ultra-thin and ultra-thick sheet components;(ii)integrated ultra-large size ring components with thin wall and high ribs;and(iii)integrated ultra-long tube components with large perimeter difference.Various plasticity technologies and process se-quences have been developed.The key processes and applications of the technologies are discussed in detail,which achieve successful plastic forming of integrated components.This paper provides state-of-the-art and perspectives for the rapidly advancing material forming fields of key metal components for the next generation of equipment.
基金Supported by the National Defense Basic Scientific Research Program of China.
文摘Amphibious vehicles are more prone to attitude instability compared to ships,making it crucial to develop effective methods for monitoring instability risks.However,large inclination events,which can lead to instability,occur frequently in both experimental and operational data.This infrequency causes events to be overlooked by existing prediction models,which lack the precision to accurately predict inclination attitudes in amphibious vehicles.To address this gap in predicting attitudes near extreme inclination points,this study introduces a novel loss function,termed generalized extreme value loss.Subsequently,a deep learning model for improved waterborne attitude prediction,termed iInformer,was developed using a Transformer-based approach.During the embedding phase,a text prototype is created based on the vehicle’s operation log data is constructed to help the model better understand the vehicle’s operating environment.Data segmentation techniques are used to highlight local data variation features.Furthermore,to mitigate issues related to poor convergence and slow training speeds caused by the extreme value loss function,a teacher forcing mechanism is integrated into the model,enhancing its convergence capabilities.Experimental results validate the effectiveness of the proposed method,demonstrating its ability to handle data imbalance challenges.Specifically,the model achieves over a 60%improvement in root mean square error under extreme value conditions,with significant improvements observed across additional metrics.
基金supported by the Science and Technology Project of Sichuan Electric Power Company“Power Supply Guarantee Strategy for Urban Distribution Networks Considering Coordination with Virtual Power Plant during Extreme Weather Event”(No.521920230003).
文摘Ensuring reliable power supply in urban distribution networks is a complex and critical task.To address the increased demand during extreme scenarios,this paper proposes an optimal dispatch strategy that considers the coordination with virtual power plants(VPPs).The proposed strategy improves systemflexibility and responsiveness by optimizing the power adjustment of flexible resources.In the proposed strategy,theGaussian Process Regression(GPR)is firstly employed to determine the adjustable range of aggregated power within the VPP,facilitating an assessment of its potential contribution to power supply support.Then,an optimal dispatch model based on a leader-follower game is developed to maximize the benefits of the VPP and flexible resources while guaranteeing the power balance at the same time.To solve the proposed optimal dispatch model efficiently,the constraints of the problem are reformulated and resolved using the Karush-Kuhn-Tucker(KKT)optimality conditions and linear programming duality theorem.The effectiveness of the strategy is illustrated through a detailed case study.
基金supported by the National Natural Science Foundation of China(Grant Nos.51777016,51607013,61601062&61801054)。
文摘Initial-dependent extreme multi-stability and offset-boosted coexisting attractors have been significantly concerned recently.This paper constructs a novel five-dimensional(5-D)two-memristor-based dynamical system by introducing two memristors with cosine memductance into a three-dimensional(3-D)linear autonomous dissipative system.Through theoretical analyses and numerical plots,the memristor initial-boosted coexisting plane bifurcations are found and the memristor initial-dependent extreme multi-stability is revealed in such a two-memristor-based dynamical system with plane equilibrium.Furthermore,a dimensionality reduction model with the determined equilibrium is established via an integral transformation method,upon which the memristor initial-dependent extreme multi-stability is reconstituted theoretically and expounded numerically.Finally,physically circuit-implemented PSIM(power simulation)simulations are carried out to validate the plane offset-boosted coexisting behaviors.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11972173 and 12172340)。
文摘We present a class of two-dimensional memristive maps with a cosine memristor. The memristive maps do not have any fixed points, so they belong to the category of nonlinear maps with hidden attractors. The rich dynamical behaviors of these maps are studied and investigated using different numerical tools, including phase portrait, basins of attraction,bifurcation diagram, and Lyapunov exponents. The two-parameter bifurcation analysis of the memristive map is carried out to reveal the bifurcation mechanism of its dynamical behaviors. Based on our extensive simulation studies, the proposed memristive maps can produce hidden periodic, chaotic, and hyper-chaotic attractors, exhibiting extremely hidden multistability, namely the coexistence of infinite hidden attractors, which was rarely observed in memristive maps. Potentially,this work can be used for some real applications in secure communication, such as data and image encryptions.
基金National Key R&D Program of China of the 13th Five-Year Plan(No.2018YFD1100704)。
文摘To meet the challenge of mismatches between power supply and demand,modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids.Furthermore,it is essential to understand the effectiveness of flexibility management strategies under different climate conditions and extreme weather events.Using both typical and extreme weather data from cities in five major climate zones of China,this study investigates the energy flexibility potential of an office building under three short-term HVAC management strategies in the context of different climates.The results show that the peak load flexibility and overall energy performance of the three short-term strategies were affected by the surrounding climate conditions.The peak load reduction rate of the pre-cooling and zone temperature reset strategies declined linearly as outdoor temperature increased.Under extreme climate conditions,the daily peak-load time was found to be over two hours earlier than under typical conditions,and the intensive solar radiation found in the extreme conditions can weaken the correlation between peak load reduction and outdoor temperature,risking the ability of a building’s HVAC system to maintain a comfortable indoor environment.
基金jointly supported by the National Natural Science Foundation of China (Grant Nos.42422502 and 42275038)the China Meteorological Administration Climate Change Special Program (Grant No.QBZ202306)funded by the Met Office Climate Science for Service Partnership (CSSP) China project under the International Science Partnerships Fund (ISPF)。
文摘This past year, 2024, is on track to be the warmest year, joining 2023 as the two hottest years on record. With the exceptional heat, weather and climate extremes were common across the world. In particular, 2024 has seen a remarkable run of extreme precipitation events and resulting impacts. Here, we provide an overview of the most notable extreme events of the year, including extreme precipitation and floods, tropical cyclones, and droughts. The characteristics and impacts of these extreme events are summarized, followed by discussion on the physical drivers and the role of global warming.Finally, we also discuss the future prospects in extreme event studies, including impact-based perspectives, challenges in attribution of precipitation extremes, and the existing gap to minimize impacts from climate extremes.
基金supported by the funding Riset Unggulan Daerah 2022 of the Bureau of Development Planning and Research in Central Java Province(BAPPEDA Provinsi Jawa Tengah).
文摘Located downstream the Kupang Catchment in Indonesia,Pekalongan faces significant land subsidence issues,leading to severe coastal flooding.This study aimed to assess the impact of climate change on future flow regimes and hydrological extremes to inform long-term water resources management strategies for the Kupang Catchment.Utilizing precipitation and air temperature data from general circulation models in the Coupled Model Intercomparison Project 6(CMIP6)and employing bias correction techniques,the Soil and Water Assessment Tool(SWAT)hydrological model was employed to analyze climate-induced changes in hydrological fluxes,specifically streamflow.Results indicated a consistent increase in monthly streamflow during the wet season,with a substantial rise of 22.8%,alongside a slight decrease of 18.0%during the dry season.Moreover,both the frequency and severity of extremely low and high flows were projected to intensify by approximately 50%and 70%,respectively,for a 20-year return period,suggesting heightened flood and drought risks in the future.The observed declining trend in low flow,by up to 11%,indicated the potential for long-term groundwater depletion exacerbating the threat of land subsidence and coastal flooding,especially in areas with inadequate surface water management policies and infrastructure.
基金supported by the National Key R&D Program of China(2022YFC3003903)Natural Science Foundation of Beijing(Grant No.8222079)and of China(Grant No.42475014,U2442204)the Basic Research Fund of CAMS(2023Z001).
文摘This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,the maximum regionalaverage HRR and site-observed HRR,which exhibited sequential development over southern,middle,and northern key regions.These rainfall extremes occurred in an environment where a high-pressure barrier over North China prevented the intrusion of cold air masses from the north while a northward-moving typhoon remnant vortex and its associated low-level jet(LLJ)transported warm and moist airflow from the south.Two distinct echo evolution modes and convection initiation mechanisms are identified for the two types of extreme HRRs.The maximum regional-average HRR occurred when the LLJ arrived to the east of the key regions,while the maximum site-observed HRR occurred when the warmer vortex center influenced the regions.Taking the northern key region as a representation,at the time of the maximum regional-average HRR,slantwise ascent of the airflow along a warm-frontal-like boundary released energy related to symmetrical instability,resulting in stratiform rainfall with weak convective cores.The transport of locally initiated convection over the eastern plain region,where the atmospheric stratification was more potentially unstable,also significantly contributed.When the maximum site-observed HRR occurred,the terrain lifting of warm and moist southeast airflow led to intense convection over the mountain foothills.Overall,the passage of the warm-core typhoon remnant vortex and interaction with Taihang Mountains determined the timing and location of extreme HRRs across the key regions.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program[grant number 2019QZKK0101]。
文摘In the context of global warming,it is anticipated that both the intensity and the frequency of future global extreme high precipitation(EHP)and extreme high temperature(EHT)events will increase.To evaluate the future extreme climate changes in the Asian arid region and Tibetan Plateau,this study applied the NASA Earth Exchange Global Daily Downscaled Projections(NEX-GDDP-CMIP6)to assess the changes in EHP(Rx5d and R95pTOT)and EHT(TX90p and TXx)under different emission scenarios in the 21st century.Findings suggest that both the frequency and the intensity of the extreme indices will increase,exhibiting accelerated growth under higher emission scenarios,particularly under the SSP5-8.5 emission scenario.It is suggested that the growth of EHT and EHP in the early subperiod of the 21st century(2026-2045)will be relatively moderate,with small differences between different emission scenarios.However,by the middle subperiod of the 21st century(2041-2060),the differences between different emission scenarios will become larger than the 2035s and the growth will become more intense.In western central Asia,TX90p,TXx,Rx5d,and R95pTOT increase by 9.7%-14.2%(13.3%-24.7%),1.3℃-1.7℃(1.6℃-2.7℃),6.5%-8.9%(8.2%-8.8%),and 18.1%-27.0%(25.6%-30.0%)by the early(middle)subperiod;in eastern central Asia,TX90p,TXx,Rx5d,and R95pTOT increase 8.1%-12.0%(11.3%-21.1%),1.4℃-1.8℃(1.9℃-2.9℃),7.4%-9.7%(10.4%-13.8%),and 20.2%-29.3%(32.0%-40.8%)by the early(middle)subperiod;and over the Tibetan Plateau,TX90p,TXx,Rx5d,and R95pTOT increase 12.5%-17.4%(17.0%-31.0%),1.2℃-1.5℃(1.6℃-2.5℃),7.2%-10.0%(9.9%-15.0%),and 26.6%-33.1%(36.1%-55.3%)by the early(middle)subperiod.
基金funded by the National Natural Science Fund of China(Nos.42442015,42274111)。
文摘1 EXTREME DROUGHT AND HYDROGEODESY TECHNOLOGIES The World Meteorological Organization has officially declared 2023 as the hottest year on record,with the average global temperature surpassing pre-industrial(1850-1900)average by 1.45℃.While temperature is not the only climate observable from the complex processes for the geneses of droughts,recent hottest years have witnessed numerous instances of extreme droughts.
基金supported by the National Natural Science Foundation of China(Grants No.42371354,42375129,42371115)the Fundamental Research Funds for National Universities,China Uni-versity of Geosciences,Wuhan.
文摘In recent years,there has been a pronounced increase in the frequency of extreme weather events.To compre hensively examine the impact of extreme weather on ecosystem services within the Wuhan Urban Agglomera tion(WUA),this study utilized meteorological station data,the Mann-Kendall(MK)test,and the Standardized Precipitation-Evapotranspiration Index(SPEI)to quantify the variation trends in heatwaves(HW)and droughts from 1961 to 2020.Then the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model was employed to evaluate and compare the differences in water yield and climate regulation ecosystem services un der various HW,droughts,and HW-drought combination scenarios.The results show that over the past 60 years,the temperature,duration,and frequency of HW have significantly increased in the WUA.Specifically,the high est HW temperature,total HW days,HW frequency,and average HW temperature showed changing trend of+0.17℃/decade,+1.4 day/decade,+0.19 event/decade,and+0.07℃/decade,respectively.The year 2000 was identified as a mutation year for HW,characterized by increased frequency and heightened severity thereafter.The SPEI value exhibited an insignificant upward trend,with 1980 marked as a mutation year,indicating a de creasing trend in drought occurrences after 1980.Heatwaves have a weakening effect on both water yield and climate regulation services,while drought significantly weakened water yield and had a relatively modest effect on climate regulation.During HW-drought composite period,the average monthly water yield showed a notable discrepancy of 60 mm compared to humid years.Besides,as heatwaves intensify,the area of low aggregation for ecosystem services expands,whereas the area of high aggregation decreases.This study provides a preliminary understanding of the impact of urban extreme weather on urban ecosystem services under changing climatic conditions.
基金supported by the National Key R&D Program of China[grant number 2022YFF0801603]the Natural Science Foundation of China[grant number 41905074].
文摘Due to the high elevation and cold climate of the Tibetan Plateau,the western region retains extensive snow cover during the summer,which can exhibit rapid variability over the course of just a few days.This study utilizes numerical experiments to investigate the atmospheric response to extreme Tibetan Plateau snow cover(TPSC)events on a subseasonal timescale during summer.The results indicate that the subseasonal variations in TPSC exert limited impact on nonlocal atmospheric circulation and temperature during this period.Nevertheless,local surface energy and atmospheric temperature exhibit rapid cooling responses to increased snow cover.Specifically,an increase in snow cover over the western Tibetan Plateau leads to a sharp rise in surface albedo,resulting in a reduction in land surface energy and a negative response in the diabatic heating rate from the surface to 350 hPa locally.This negative diabatic heating response subsequently causes a decline in both surface and overlying atmospheric temperatures.The temperature response is confined to the western Tibetan Plateau and extends vertically from the surface to approximately 350 hPa.These extreme TPSC events and their associated atmospheric impacts occur within a two-week timescale.
基金financially supported by the National Key R&D Program of China(Grant No.2022YFC2204203)the National Natural Science Foundation of China(Grant No.52305107)。
文摘Precision actuation is a foundational technology in high-end equipment domains,where stroke,velocity,and accuracy are critical for processing and/or detection quality,precision in spacecraft flight trajectories,and accuracy in weapon system strikes.Piezoelectric actuators(PEAs),known for their nanometer-level precision,flexible stroke,resistance to electromagnetic interference,and scalable structure,have been widely adopted across various fields.Therefore,this study focuses on extreme scenarios involving ultra-high precision(micrometer and beyond),minuscule scales,and highly complex operational conditions.It provides a comprehensive overview of the types,working principles,advantages,and disadvantages of PEAs,along with their potential applications in piezo-actuated smart mechatronic systems(PSMSs).To address the demands of extreme scenarios in high-end equipment fields,we have identified five representative application areas:positioning and alignment,biomedical device configuration,advanced manufacturing and processing,vibration mitigation,micro robot system.Each area is further divided into specific subcategories,where we explore the underlying relationships,mechanisms,representative schemes,and characteristics.Finally,we discuss the challenges and future development trends related to PEAs and PSMSs.This work aims to showcase the latest advancements in the application of PEAs and provide valuable guidance for researchers in this field.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3003805)Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2022356)Guangzhou Basic and Applied Basic Research Project(Grant No.2023A04J0955).
文摘This paper presents a new type of triangular Sharp Eagle wave energy converter(WEC)platform.On the basis of the linear potential flow theory and the finite element analysis method,the hydrodynamic performance and structural response of the platform are studied,considering the actual platform motion and free surface rise under extreme sea states.First,the effects of the wave frequency and direction on the wave-induced loads and dynamic responses were examined.The motion at a wave direction angle of 0°is relatively low.On this basis,the angle constrained by the two sides of the Sharp Eagle floaters should be aligned with the main wave direction to avoid significant platform motion under extreme sea states.Additionally,the structural response of the platform,including the wave-absorbing floaters,is investigated.The results highlighted that the conditions or locations where yielding,buckling,and fatigue failures occur were different.In this context,the connection area of the Sharp Eagle floaters and platform is prone to yielding failure under oblique wave action,whereas the pontoon and side of the Sharp Eagle floaters are prone to buckling failure during significant vertical motion.Additionally,fatigue damage is most likely to occur at the connection between the middle column on both sides of the Sharp Eagle floaters and the pontoons.The findings of this paper revealed an intrinsic connection between wave-induced loads and the dynamic and structural responses of the platform,which provides a useful reference for the improved design of WECs.
基金supported by the National Natural Science Foundation of China(72072169)the Fundamental Re-search Funds for the Central Universities(YD2040002015).
文摘The impact of extreme temperatures on the health of individuals in different organizations remains uncertain.We employed stratified analyses to examine the impacts of summer(April-September)daily maximum temperatures and winter(October-March)daily minimum temperatures on blood pressure and lipid profiles across government staff,com-pany employees,and researchers.We examined 209,477 physical examination records from a physical examination center in the First Affiliated Hospital of USTC from 2017 to 2021.Employing a segmented regression model within the frame-work of generalized linear regression(GLM),we examined the causal impact of extreme temperatures on health outcomes.Additionally,sensitivity analyses were conducted via distributed lag nonlinear models(DLNMs),with a focus on ob-serving the long-term effects over a period of 21 days.Our findings indicate that government staff face increased health risks during extremely low temperatures,regardless of the season.Compared with participants experiencing median tem-peratures,government staff exposed to extremely low temperatures(below the 10th percentile,below 24℃)in the sum-mer presented maximum increases of 2.32 mmHg(95%CI:1.542-3.098)in diastolic blood pressure and 6.481 mmHg(95%CI:5.368-7.594)in systolic blood pressure.In winter,government staff exposed to temperatures below the 10th per-centile(below 1℃)demonstrated maximum increases of 0.278 mmol/L(95%CI:0.210-0.346)in total cholesterol,0.153 mmol/L(95%CI:0.032-0.274)in triglycerides,and 0.077 mmol/L(95%CI:0.192-0.134)in low-density lipoprotein.Conversely,warm winters benefit company employees,whereas researchers exhibit lower sensitivity to temperature changes in winter.The maximum temperatures in summer and minimum temperatures in winter had greater impacts on in-dividuals.Small temperature fluctuations impact health more than large changes do.Notably,both the maximum and min-imum temperatures were better predictors of health outcomes than the daily average temperature was.Blood pressure con-sistently displayed significant associations with temperature across all three groups,with extremely low temperatures in-creasing the risk and extremely high temperatures reducing it.However,the relationship between temperature and blood lipids is complex.
基金supported by the National Key R&D Program of China(2022YFE0106300)Norges Forskningsråd(328886).
文摘This study investigates trends in extreme precipitation events(EPEs)across Antarctica from 1979 to 2023,analyzing changes in EPE frequency,intensity,and the proportion of extreme to total precipitation.Using Self-Organizing Map(SOM)techniques,the study distinguishes the contributions from thermodynamic,dynamic,and interaction components in explaining these trends.Positive EPE occurrence trends are observed across the Bellingshausen and Weddell Seas,Dronning Maud Land,and parts of the Southern Ocean,with declines limited to Queen Mary Land.Thermodynamic factors,responsible for 96.0%of the overall trend,are driven by increased water vapor content in polar air masses.Dynamic contributions,representing 10.8%,are linked to a strengthened Amundsen Sea Low(ASL)associated with the Southern Annular Mode(SAM)and Pacific South American(PSA)trends.Interaction effects make a slightly negative contribution(-6.8%)to the overall trend.Variations in water vapor transport and vertical velocity tied to annual 500-hPa geopotential height anomalies further explain EPE trends.These findings provide insight into the atmospheric processes that influence Antarctic EPEs,with implications for understanding the climatic impact on the polar environment.
基金supported by the National Natural Science Foundation of China(Grant Nos.42150204 and 2288101)supported by the China National Postdoctoral Program for Innovative Talents(BX20230045)the China Postdoctoral Science Foundation(2023M730279)。
文摘A nonlinear multi-scale interaction(NMI)model was proposed and developed by the first author for nearly 30 years to represent the evolution of atmospheric blocking.In this review paper,we first review the creation and development of the NMI model and then emphasize that the NMI model represents a new tool for identifying the basic physics of how climate change influences mid-to-high latitude weather extremes.The building of the NMI model took place over three main periods.In the 1990s,a nonlinear Schr?dinger(NLS)equation model was presented to describe atmospheric blocking as a wave packet;however,it could not depict the lifetime(10-20 days)of atmospheric blocking.In the 2000s,we proposed an NMI model of atmospheric blocking in a uniform basic flow by making a scale-separation assumption and deriving an eddyforced NLS equation.This model succeeded in describing the life cycle of atmospheric blocking.In the 2020s,the NMI model was extended to include the impact of a changing climate mainly by altering the basic zonal winds and the magnitude of the meridional background potential vorticity gradient(PVy).Model results show that when PVy is smaller,blocking has a weaker dispersion and a stronger nonlinearity,so blocking can be more persistent and have a larger zonal scale and weaker eastward movement,thus favoring stronger weather extremes.However,when PVy is much smaller and below a critical threshold under much stronger winter Arctic warming of global warming,atmospheric blocking becomes locally less persistent and shows a much stronger westward movement,which acts to inhibit local cold extremes.Such a case does not happen in summer under global warming because PVy fails to fall below the critical threshold.Thus,our theory indicates that global warming can render summer-blocking anticyclones and mid-to-high latitude heatwaves more persistent,intense,and widespread.
基金This study was jointly supported by the National Natural Science Foundation of China(Nos.51879196,51790533,51709143)Jiangxi Natural Science Foundation of China(No.20181BAB206045).
文摘It is important for regional water resources management to know the agricultural water consumption information several months in advance.Forecasting reference evapotranspiration(ET_(0))in the next few months is important for irrigation and reservoir management.Studies on forecasting of multiple-month ahead ET_(0) using machine learning models have not been reported yet.Besides,machine learning models such as the XGBoost model has multiple parameters that need to be tuned,and traditional methods can get stuck in a regional optimal solution and fail to obtain a global optimal solution.This study investigated the performance of the hybrid extreme gradient boosting(XGBoost)model coupled with the Grey Wolf Optimizer(GWO)algorithm for forecasting multi-step ahead ET_(0)(1-3 months ahead),compared with three conventional machine learning models,i.e.,standalone XGBoost,multi-layer perceptron(MLP)and M5 model tree(M5)models in the subtropical zone of China.The results showed that theGWO-XGB model generally performed better than the other three machine learning models in forecasting 1-3 months ahead ET_(0),followed by the XGB,M5 and MLP models with very small differences among the three models.The GWO-XGB model performed best in autumn,while the MLP model performed slightly better than the other three models in summer.It is thus suggested to apply the MLP model for ET_(0) forecasting in summer but use the GWO-XGB model in other seasons.
