Convectively unstable processes caused by dense water subsidence are common occurrences in high-latitude oceanic regions,and significantly modulate mass and heat transport and mixing processes in the ocean.An idealize...Convectively unstable processes caused by dense water subsidence are common occurrences in high-latitude oceanic regions,and significantly modulate mass and heat transport and mixing processes in the ocean.An idealized numerical experiment using the large eddy simulation method was conducted to analyze the three-dimensional flow field structure and the mechanism for dense water subsidence.Specifically,a negative salt flux is set at the sea surface,in which salt flux enters the sea surface to simulate the icing and salting-out phenomena that occur at high latitudes.Results show that the mean-state 3D flow field of dense water subsidence exhibits a hollow conical distribution.The horizontal flow field is characterized by a cyclonic vortex that driven primarily by the pressure gradient and influenced by the Coriolis effect.Moreover,the inverse vertical pressure gradient generated by this vortex inhibits the sinking of the plume,leading to its off-axis deflection and the development of an anticyclonic precession.In addition,the impact of rotation on the structure of a sinking plume within a stratified environment is discussed.Both horizontal vortex intensity and cone angle of the hollow cone flow field are increased with increasing rotation rate,resulting in a decrease in the plume’s maximum sinking depth.Variances in rotation direction cause the horizontal vortex and sinking plumes of dense water in the northern and southern hemispheres to rotate in opposite directions.展开更多
Fluid flow through porous spaces with variable porosity has wide-range applications,notably in biomedical and thermal engineering,where it plays a vital role in comprehending blood flow dynamics within cardiovascular ...Fluid flow through porous spaces with variable porosity has wide-range applications,notably in biomedical and thermal engineering,where it plays a vital role in comprehending blood flow dynamics within cardiovascular systems,heat transfer and thermal management systems improve efficiency using porous materials with variable porosity.Keeping these important applications in view,in current study blood-based hybrid nanofluid flow has considered on a convectively heated sheet.The sheet exhibits the properties of a porous medium with variable porosity and extends in both the x and y directions.Blood has used as base fluid in which the nanoparticles of Cu and Cu O have been mixed.Thermal radiation,space-dependent,and thermal-dependent heat sources have been incorporated into the energy equation,while magnetic effects have been integrated into the momentum equations.Dimensionless variables have employed to transform the modeled equations into dimensionless form and facilitating their solution using bvp4c approach.It has concluded in this study that,both the primary and secondary velocities augmented with upsurge in variable porous factor and declined with escalation in stretching ratio,Casson,magnetic,and slip factors along x-and y-axes.Thermal distribution has grown up with upsurge in Casson factor,magnetic factor,thermal Biot number,and thermal/space-dependent heat sources while has retarded with growth in variable porous and stretching ratio factors.The findings of this investigation have been compared with the existing literature,revealing a strong agreement among present and established results that ensured the validation of the model and method used in this work.展开更多
It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the i...It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the invalidity of parcel theory. However, evidence shows that the convective Richardson number Ri* might be an improper characteristic scaling parameter for the entrainment process. An attempt to use an innovative parameter to parameterize the entrainment-zone thickness has been made in this paper. Based on the examination of the data of water-tank experiments and atmospheric measurements, it is found that the total lapse rate of potential temperature across the entrainment zone is proportional to that of the capping inversion layer. Inserting this relationship into the so-called parcel theory, it thus gives a new parameterization scheme for the depth of the entrainment zone. This scheme includes the lapse rate of the capping inversion layer that plays an important role in the entrainment process. Its physical representation is reasonable. The new scheme gives a better ordering of the data measured in both water-tank and atmosphere as compared with the traditional method using Ri*. These indicate that the parcel theory can describe the entrainment process suitably and that the new parameter is better than Ri*.展开更多
The effect of nonlinear mixed convection in stretched flows of rate-type nonNewtonian materials is described. The formulation is based upon the Maxwell liquid which elaborates thermal relation time characteristics. Na...The effect of nonlinear mixed convection in stretched flows of rate-type nonNewtonian materials is described. The formulation is based upon the Maxwell liquid which elaborates thermal relation time characteristics. Nanofluid properties are studied considering thermophoresis and Brownian movement. Thermal radiation, double stratification, convective conditions, and heat generation are incorporated in energy and nanoparticle concentration expressions. A boundary-layer concept is implemented for the simplification of mathematical expressions. The modeled nonlinear problems are computed with an optimal homotopy scheme. Moreover, the Nusselt and Sherwood numbers as well as the velocity, nanoparticle concentration, and temperature are emphasized. The results show opposite impacts of the Deborah number and the porosity factor on the velocity distribution.展开更多
The Atlantic Meridional Overturning Circulation(AMOC)serves as an important conduit for poleward heat transport in the global ocean,playing a crucial role in regulating global climate.However,biases have been found in...The Atlantic Meridional Overturning Circulation(AMOC)serves as an important conduit for poleward heat transport in the global ocean,playing a crucial role in regulating global climate.However,biases have been found in multi-model simulations of AMOC,particularly due to inaccuracies in convective mixing parameterization,which leads to an overestimation of convective mixing depth in the Labrador Sea and Nordic Seas.This excessive deep convection results in stronger simulated AMOC transport compared to observations.Therefore,this study employs the Large Eddy Simulation(LES)method to simulate the sinking process of dense water using a series of idealized experiments with various sea surface salt flux,latitude,and ocean stratification.The results show that increased salt flux forcing and weakened background stratification both enhance the sinking of dense water,with geographical location(latitude)exerting a discernable impact.Based on these insights,the eddy viscosity coefficient,which characterizes vertical convective mixing in the parameterization scheme,is refined,with adjustments to its vertical structure and the incorporation of latitude dependence.It is preliminarily applied to simulate AMOC using the Community Earth System Model(CESM).The results demonstrate improvements in the simulation accuracy of seawater temperature at the near-surface and deep layers.Including the parameterization scheme of dense water sinking in the model leads to a reduction in the simulated intensity of AMOC at 26.5°N.In the high-latitude North Atlantic,the modification implemented in parameterization results in notable improvements in the simulation of seawater temperature,salinity,and density,with respective reductions in their root mean square errors of 4.36%,19.77%,and 1.84%.展开更多
The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model perfo...The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model performance in simulating the convectively coupled equatorial waves(CCEWs) by comparing the daily output of precipitation from a 23-yr coupled run with the observational precipitation data from Global Precipitation Climatology Project(GPCP). Four dominant modes of CCEWs including the Kelvin, equatorial Rossby(ER), mixed Rossby–gravity(MRG), tropical depression-type(TD-type) waves, and their annual mean and seasonal cycle characteristics are investigated respectively. It is found that the space–time spectrum characteristics of each wave mode represented by tropical averaged precipitation could be very well simulated by CAMS-CSM, including the magnitudes and the equivalent depths. The zonal distribution of wave associated precipitation is also well simulated, with the maximum centers over the Indian Ocean and the Pacific Ocean. However, the meridional distribution of the wave activities is poorly simulated, with the maximum centers shifted from the Northern Hemisphere to the Southern Hemisphere, especially the Kelvin, MRG, and TD waves. The seasonal cycle of each wave mode is generally captured by the model, but their amplitudes over the Southern Hemisphere during boreal winter are grossly overestimated. The reason for the excessive wave activity over the southern Pacific Ocean in the simulation is discussed.展开更多
The influence of E1 Nifio-Southern Oscillation （ENSO） on the convectively coupled Kelvin waves over the tropical Pacific is investigated by comparing the Kelvin wave activity in the eastern Pacific （EP） E1 Nifio, ...The influence of E1 Nifio-Southern Oscillation （ENSO） on the convectively coupled Kelvin waves over the tropical Pacific is investigated by comparing the Kelvin wave activity in the eastern Pacific （EP） E1 Nifio, central Pacific （CP） E1 Nifio, and La Nifia years, respectively, to 30-yr （1982 2011） mean statistics. The convectively coupled Kelvin waves in this study are represented by the two leading modes of empirical orthogonal function （EOF） of 2-25-day band-pass filtered daily outgoing longwave radiation （OLR）, with the estimated zonal wavenumber of 3 or 4, period of 8 days, and eastward propagating speed of 17 m s-1. The most significant impact of ENSO on the Kelvin wave activity is the intensification of the Kelvin waves during the EP E1 Nifios. The impact of La Nifia on the reduction of the Kelvin wave intensity is relatively weaker, reflecting the nonlinearity of tropical deep convection and the associated Kelvin waves in response to ENSO sea surface temperature （SST） anomalies. The impact of the CP E1 Nifio on the Kelvin waves is less significant due to relatively weaker SST anomalies and smaller spatial coverage. ENSO may also alter the frequency, wavelength, and phase speed of the Kelvin waves. This study demonstrates that low- frequency ENSO SST anomalies modulate high-frequency tropical disturbances, an example of weather- climate linkage.展开更多
This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic li...This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic linkages with Northeast China cold vortices(NCCVs)of tornadic storms under different convective modes.Results reveal that discrete storms account for 70%of events,with clustered cells(CC)being the most frequent mode,while significant tornadoes(EF2+)are primarily associated with isolated cells(IC)and broken lines(BL).The storm mode distribution in northeastern China resembles that of the central United States but with a higher proportion of CC and lower IC.In contrast,southern China exhibits a higher frequency of quasi-linear(QL)modes(>50%),similar to European patterns.Although no single parameter clearly differentiates between all tornado modes,distinct morphological characteristics emerge through specific parameter combinations:NL modes are characterized by high 0-1 km storm-relative helicity(SRH1)and humidity but low 0-6 km shear(SR6),whereas IC modes display contrasting features with low SRH1 and high CAPE.Notably,83%of tornadoes are associated with NCCVs,preferentially forming in southeastern/southwestern quadrants.Strong tornadoes favor southeastern quadrants,while NCCV intensity correlates with tornadic distance from vortex centers.Three characteristic synoptic configurations emerge:(T1)strong deep vortices with vertically aligned cold troughs,generating southeast-dominant tornado clusters characterized by a high proportion of BL and QL modes;(T2)weaker vortices featuring sub-synoptic troughs,with southern-distributed events dominated by a predominance of the CC mode;(T3)transverse-trough systems exhibiting CAPE-SRH decoupling and reduced tornadic activity.This study enhances our understanding of tornadoes in northeastern China,informing future research on formation mechanisms,prediction methods,and disaster prevention strategies.展开更多
The theoretical analysis of the mixed convective Buongiorno nanofluid flow in an inclined annular microchannel with convectively heated walls subjected to the effects of nonlinear thermal radiation,exponential heat so...The theoretical analysis of the mixed convective Buongiorno nanofluid flow in an inclined annular microchannel with convectively heated walls subjected to the effects of nonlinear thermal radiation,exponential heat source(EHS),thermal dependent heat source(THS)is carried out.The description of the Buongiorno nanofluid is implemented to analyze the Brownian diffusion and thermo-migration mechanisms.The general boundary conditions for the velocity,thermal,and nanoparticle volume fraction(NVF)are considered.Numerical solutions for fully developed governing equations are obtained using bvp5c solver and verified with FEM.The optimization of heat transport rates is made by using the Box-Behnken designbased response surface method.It is found that the Lorentz force and the inclination angle of the annulus significantly affect the rheological characteristics of the nanofluid.Nanoparticles increase thermal energy in the system through Brownian diffusion and thermophoresis,resulting in increased temperature field.Internal heat sources would serve as an important tool for modulating the thermal field in microchannel,as they are directly associated.At low-level values of the thermal Biot number,the exponential heat source,and the thermal radiation parameter,it is possible to attain the maximum Nusselt number on both walls of the annulus.展开更多
Low-angle grain boundaries(LAGBs)are one of the solidification defects in single-crystal nickel-based superalloys and are detrimental to the mechanical properties.The formation of LAGBs is related to dendrite deformat...Low-angle grain boundaries(LAGBs)are one of the solidification defects in single-crystal nickel-based superalloys and are detrimental to the mechanical properties.The formation of LAGBs is related to dendrite deformation,while the mechanism has not been fully understood at the mesoscale.In this work,a model coupling dendrite growth,thermal-solutal-fluid flow,thermal stress and flow-induced dendrite deformation via cellular automaton-finite volume method and finite element method is developed to study the formation of LAGBs in single crystal superalloys.Results reveal that the bending of dendrites is primarily attributed to the thermal-solutal convection-induced dendrite deformation.The mechanical stress of dendrite deformation develops and stabilises as solidification proceeds.As the width of the mushy zone gets stable,stresses are built up and then dendritic elastoplastic bending occurs at some thin primary dendrites with the wider inter-dendritic space.There are three characteristic zones of stress distribution along the solidification direction:(i)no stress concentration in the fully solidified regions;(ii)stress developing in the primary dendrite bridging region,and(iii)stress decrease in the inter-dendritic uncontacted zone.The stresses reach maximum near the initial dendrite bridging position.The lower temperature gradients,the finer primary dendritic trunks and sudden reductions in local dendritic trunk radius jointly promote the elastoplastic deformation of the dendrites.Corresponding measures are suggested to reduce LAGBs.展开更多
On 19 May 2022, an outbreak of 105 red sprites that occurred over South Asia was fortuitously recorded by two amateurs from a site in the southern Tibetan Plateau(TP), marking the highest number captured over a single...On 19 May 2022, an outbreak of 105 red sprites that occurred over South Asia was fortuitously recorded by two amateurs from a site in the southern Tibetan Plateau(TP), marking the highest number captured over a single thunderstorm in South Asia. Nearly half of these events involved dancing sprites, with an additional 16 uncommon secondary jets and at least four extremely rare green emissions called “ghosts” observed following the associated sprites. Due to the absence of the precise timing needed to identify parent lightning, a method based on satellite motion trajectories and star fields is proposed to infer video frame timestamps within an error of less than one second. After verifying 95 sprites from two videos, our method identified the parent lightning for 66 sprites(~70%). The sprite-producing strokes, mainly of positive polarity with peak currents exceeding +50 k A, occurred in the stratiform region of a mesoscale convective complex(MCC)that spanned the Ganges Plain to the southern TP, with a cloud area over 200 000 km2 and a minimum cloud-top black body temperature near 180 K. This observation confirms that thunderstorms in South Asia, akin to mesoscale convective systems(MCSs) in the Great Plains of the United States or coastal thunderstorms in Europe, can produce numerous sprites,including complex species. Our analysis bears important implications for characterizing thunderstorms above the southern TP and examining their physical and chemical effects on the adjacent regions, as well as the nature of the coupling between the troposphere and middle-upper atmosphere in this region.展开更多
The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practi...The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.展开更多
The wetting behavior of liquid tin(Sn)solder on copper(Cu)substrate at 250℃was investigated by the wetting balance method under the action of direct current(DC).The curves of wetting balance were measured and the mor...The wetting behavior of liquid tin(Sn)solder on copper(Cu)substrate at 250℃was investigated by the wetting balance method under the action of direct current(DC).The curves of wetting balance were measured and the morphology of the intermetallic compound(IMC)precipitated at the interface were observed.Results show that DC has a significant effect on the wettability and IMC.As the current increases,the balance wetting force and the thickness of the IMC layer increase.The direction of the DC also has a certain effect on the balance wetting force and IMC layer.When the current is negative,the final balance wetting force and the thickness of the Cu_(6)Sn_(5) layer are significantly higher than those in the positive current case,which is attributed to electromigration.The IMC precipitation at the interface provides a chemical driving force for the movement of the triple junction.The interaction of the interface atoms and the chemical reaction are enhanced by DC,thereby improving wettability.Meanwhile,the Marangoni convection caused by DC inside liquid Sn solder changes the structure of triple junction,which provides a physical driving force for the spread of the liquid Sn solder on the Cu substrate.展开更多
The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdraw...The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.展开更多
Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied.The centrifugal force plays a stabilizing role,while thermal convection is determined by the...Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied.The centrifugal force plays a stabilizing role,while thermal convection is determined by the“thermovibrational mechanism”.Convective flow is excited due to oscillations of a non-isothermal rotating fluid.Thermal vibrational convectionmanifests in the form of two-dimensional vortices elongated along the axis of rotation,which develop in a threshold manner with an increase in the amplitude of fluid oscillations.The objective of the present study is to clarify the nature of another phenomenon,i.e.,three-dimensional convective vortices observed in the experiments both before the excitation of the convection described above and in the supercritical region.The experimental study of the oscillatory and the time-averaged flow fields by particle image velocimetry is accompanied by the theoretical research of inertial waves.It is found that three-dimensional fluid flows owe their origin to inertial waves.This is confirmed by a high degree of agreement between the experimental and theoretical results.Experiments with cavities of different lengths indicate that the vortices are clearly seen in cavities thatmeet the conditions of resonant excitation of inertial modes.Furthermore,the length of the cavity has no effect on heat transfer,which is explained by the comparatively low intensity of the wave-induced flows.The main contribution to heat transfer is due to vortices elongated along the axis of rotation.The novel results are of significant practical importance in various fields.展开更多
Understanding the complex interaction between heat and mass transfer in non-Newtonian microflows is essential for the development and optimization of efficient microfluidic and thermal management systems.This study in...Understanding the complex interaction between heat and mass transfer in non-Newtonian microflows is essential for the development and optimization of efficient microfluidic and thermal management systems.This study investigates the magnetohydrodynamic(MHD)thermosolutal convection of a Casson fluid within an inclined,porous microchannel subjected to convective boundary conditions.The nonlinear,coupled equations governing momentum,energy,and species transport are solved numerically using the MATLAB bvp4c solver,ensuring high numerical accuracy and stability.To identify the dominant parameters influencing flow behavior and to optimize transport performance,a comprehensive hybrid optimization framework—combining a modified Taguchi design,Grey Relational Analysis(GRA),and Principal Component Analysis(PCA)—is proposed.This integrated strategy enables the simultaneous assessment of skin friction,Nusselt number,and Sherwood number,providing a rigorous multi-objective evaluation of system performance.Comparative validation with benchmark results from the literature confirms the accuracy and reliability of the present formulation and its numerical implementation.The results highlight the intricate coupling among flow slip,buoyancy effects,and convective transport mechanisms.Increased slip flow enhances axial velocity,while a higher solutal Biot number intensifies concentration gradients near the channel walls.Conversely,a lower thermal Biot number diminishes the temperature field,indicating weaker heat transfer across the boundaries.PCA results reveal that the first principal component(PC1)accounts for most of the system variance,demonstrating the dominant influence of coupled flow and transport parameters on overall system performance.展开更多
This study examines the intricate occurrences of thermal and solutal Marangoni convection in three-layered flows of viscous fluids,with a particular emphasis on their relevance to renewable energy systems.This researc...This study examines the intricate occurrences of thermal and solutal Marangoni convection in three-layered flows of viscous fluids,with a particular emphasis on their relevance to renewable energy systems.This research examines the flow of a three-layered viscous fluid,considering the combined influence of heat and solutal buoyancy driven Rayleigh-Bénard convection,as well as thermal and solutal Marangoni convection.The homotopy perturbation method is used to examine and simulate complex fluid flow and transport phenomena,providing important understanding of the fundamental physics and assisting in the optimization of various battery configurations.The inquiry examines the primary elements that influence Marangoni convection and its impact on battery performance,providing insights on possible enhancements in energy storage devices.The findings indicate that the velocity profiles shown graphically exhibit a prominent core zone characterized by the maximum speed,which progressively decreases as it approaches the walls of the channel.This study enhances our comprehension of fluid dynamics and the transmission of heat and mass in intricate systems,which has substantial ramifications for the advancement of sustainable energy solutions.展开更多
Accurately simulating mesoscale convective systems(MCSs)is essential for predicting global precipitation patterns and extreme weather events.Despite the ability of advanced models to reproduce MCS climate statistics,c...Accurately simulating mesoscale convective systems(MCSs)is essential for predicting global precipitation patterns and extreme weather events.Despite the ability of advanced models to reproduce MCS climate statistics,capturing extreme storm cases over complex terrain remains challenging.This study utilizes the Global–Regional Integrated Forecast System(GRIST)with variable resolution to simulate an eastward-propagating MCS event.The impact of three microphysics schemes,including two single-moment schemes(WSM6,Lin)and one double-moment scheme(Morrison),on the model sensitivity of MCS precipitation simulations is investigated.The results demonstrate that while all the schemes capture the spatial distribution and temporal variation of MCS precipitation,the Morrison scheme alleviates overestimated precipitation compared to the Lin and WSM6 schemes.The ascending motion gradually becomes weaker in the Morrison scheme during the MCS movement process.Compared to the runs with convection parameterization,the explicit-convection setup at 3.5-km resolution reduces disparities in atmospheric dynamics due to microphysics sensitivity in terms of vertical motions and horizontal kinetic energy at the high-wavenumber regimes.The explicit-convection setup more accurately captures the propagation of both main and secondary precipitation centers during the MCS development,diminishing the differences in both precipitation intensity and propagation features between the Morrison and two single-moment schemes.These findings underscore the importance of microphysics schemes for global nonhydrostatic modeling at the kilometer scale.The role of explicit convection for reducing model uncertainty is also outlined.展开更多
Taking short-duration heavy rainfall and convective wind gusts as examples, the present study examined the characteristics of radar reflectivity and several convective parameters. We analyzed nowcasting techniques by ...Taking short-duration heavy rainfall and convective wind gusts as examples, the present study examined the characteristics of radar reflectivity and several convective parameters. We analyzed nowcasting techniques by integrating a high-resolution numerical weather prediction model with these convective parameters. Based on the CMA-GD 1-km model and its assimilation system, we conducted repeated tests on radar reflectivity data assimilation and analyzed their impact on nowcasting accuracy. Based on these analyses, we proposed a method to improve model forecasts using the useful indicative information provided by high-frequency radar reflectivity data and convective parameters. The improved method was applied to the CMA-GD 1-km model for nowcasting tests. Evaluations from batch tests and case analysis show that the proposed method significantly reduced the model's false alarm rates and improved its nowcasting performance.展开更多
This research focuses on developing innovative hybrid solar dryers that combine solar Photovoltaic(PV)and solar thermal systems for sustainable food preservation in Pakistan,addressing the country’s pressing issues o...This research focuses on developing innovative hybrid solar dryers that combine solar Photovoltaic(PV)and solar thermal systems for sustainable food preservation in Pakistan,addressing the country’s pressing issues of high post-harvest losses and unreliable energy sources.The proposed active hybrid solar dryer features a drying cabinet,two Direct Current(DC)fans for forced convection,and a resistive heating element powered by a 180 W solar PV panel.An energy-storing battery ensures continuous supply to the auxiliaries during periods of low solar irradiance,poor weather conditions,or nighttime.Tomatoes,a delicate and in-demand crop,were selected for experimentation due to their high perishability.Three experiments were conducted on the same prototype:natural convection direct solar dryer(NCDSD),forced convection direct solar dryer(FCDSD),and forced convection hybrid solar dryer(FCHSD).Each experiment began with 0.2 kg of tomatoes at 94%moisture content,achieving significant reductions:28.57%with NCDSD,16.667%with FCDSD,and 16.667%with FCHSD.The observed drying rates varied:1.161 kg/h for NCDSD,2.062 kg/h for FCDSD,and 2.8642 kg/h for FCHSD.This study presents a comparative analysis of efficiency,drying rate,and cost-effectiveness,alongside the system’s economic and environmental feasibility.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.42250710152,42192562)the Southern Laboratory of Ocean Science and Engineering(Guangdong Zhuhai)(No.SML 2020 SP 007)。
文摘Convectively unstable processes caused by dense water subsidence are common occurrences in high-latitude oceanic regions,and significantly modulate mass and heat transport and mixing processes in the ocean.An idealized numerical experiment using the large eddy simulation method was conducted to analyze the three-dimensional flow field structure and the mechanism for dense water subsidence.Specifically,a negative salt flux is set at the sea surface,in which salt flux enters the sea surface to simulate the icing and salting-out phenomena that occur at high latitudes.Results show that the mean-state 3D flow field of dense water subsidence exhibits a hollow conical distribution.The horizontal flow field is characterized by a cyclonic vortex that driven primarily by the pressure gradient and influenced by the Coriolis effect.Moreover,the inverse vertical pressure gradient generated by this vortex inhibits the sinking of the plume,leading to its off-axis deflection and the development of an anticyclonic precession.In addition,the impact of rotation on the structure of a sinking plume within a stratified environment is discussed.Both horizontal vortex intensity and cone angle of the hollow cone flow field are increased with increasing rotation rate,resulting in a decrease in the plume’s maximum sinking depth.Variances in rotation direction cause the horizontal vortex and sinking plumes of dense water in the northern and southern hemispheres to rotate in opposite directions.
基金supported via funding from Prince Sattam bin Abdulaziz University(Grant No.PSAU/2024/R/1446)。
文摘Fluid flow through porous spaces with variable porosity has wide-range applications,notably in biomedical and thermal engineering,where it plays a vital role in comprehending blood flow dynamics within cardiovascular systems,heat transfer and thermal management systems improve efficiency using porous materials with variable porosity.Keeping these important applications in view,in current study blood-based hybrid nanofluid flow has considered on a convectively heated sheet.The sheet exhibits the properties of a porous medium with variable porosity and extends in both the x and y directions.Blood has used as base fluid in which the nanoparticles of Cu and Cu O have been mixed.Thermal radiation,space-dependent,and thermal-dependent heat sources have been incorporated into the energy equation,while magnetic effects have been integrated into the momentum equations.Dimensionless variables have employed to transform the modeled equations into dimensionless form and facilitating their solution using bvp4c approach.It has concluded in this study that,both the primary and secondary velocities augmented with upsurge in variable porous factor and declined with escalation in stretching ratio,Casson,magnetic,and slip factors along x-and y-axes.Thermal distribution has grown up with upsurge in Casson factor,magnetic factor,thermal Biot number,and thermal/space-dependent heat sources while has retarded with growth in variable porous and stretching ratio factors.The findings of this investigation have been compared with the existing literature,revealing a strong agreement among present and established results that ensured the validation of the model and method used in this work.
基金This paper was supported by the National Natural Science Foundation of China under Grant Nos.40105002 and 40333027.
文摘It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the invalidity of parcel theory. However, evidence shows that the convective Richardson number Ri* might be an improper characteristic scaling parameter for the entrainment process. An attempt to use an innovative parameter to parameterize the entrainment-zone thickness has been made in this paper. Based on the examination of the data of water-tank experiments and atmospheric measurements, it is found that the total lapse rate of potential temperature across the entrainment zone is proportional to that of the capping inversion layer. Inserting this relationship into the so-called parcel theory, it thus gives a new parameterization scheme for the depth of the entrainment zone. This scheme includes the lapse rate of the capping inversion layer that plays an important role in the entrainment process. Its physical representation is reasonable. The new scheme gives a better ordering of the data measured in both water-tank and atmosphere as compared with the traditional method using Ri*. These indicate that the parcel theory can describe the entrainment process suitably and that the new parameter is better than Ri*.
文摘The effect of nonlinear mixed convection in stretched flows of rate-type nonNewtonian materials is described. The formulation is based upon the Maxwell liquid which elaborates thermal relation time characteristics. Nanofluid properties are studied considering thermophoresis and Brownian movement. Thermal radiation, double stratification, convective conditions, and heat generation are incorporated in energy and nanoparticle concentration expressions. A boundary-layer concept is implemented for the simplification of mathematical expressions. The modeled nonlinear problems are computed with an optimal homotopy scheme. Moreover, the Nusselt and Sherwood numbers as well as the velocity, nanoparticle concentration, and temperature are emphasized. The results show opposite impacts of the Deborah number and the porosity factor on the velocity distribution.
基金supported by the National Natural Science Foundation of China(Grant Nos.42250710152,42192562&42406022)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX24_1442)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)funded project(Grant No.SML2020SP007)。
文摘The Atlantic Meridional Overturning Circulation(AMOC)serves as an important conduit for poleward heat transport in the global ocean,playing a crucial role in regulating global climate.However,biases have been found in multi-model simulations of AMOC,particularly due to inaccuracies in convective mixing parameterization,which leads to an overestimation of convective mixing depth in the Labrador Sea and Nordic Seas.This excessive deep convection results in stronger simulated AMOC transport compared to observations.Therefore,this study employs the Large Eddy Simulation(LES)method to simulate the sinking process of dense water using a series of idealized experiments with various sea surface salt flux,latitude,and ocean stratification.The results show that increased salt flux forcing and weakened background stratification both enhance the sinking of dense water,with geographical location(latitude)exerting a discernable impact.Based on these insights,the eddy viscosity coefficient,which characterizes vertical convective mixing in the parameterization scheme,is refined,with adjustments to its vertical structure and the incorporation of latitude dependence.It is preliminarily applied to simulate AMOC using the Community Earth System Model(CESM).The results demonstrate improvements in the simulation accuracy of seawater temperature at the near-surface and deep layers.Including the parameterization scheme of dense water sinking in the model leads to a reduction in the simulated intensity of AMOC at 26.5°N.In the high-latitude North Atlantic,the modification implemented in parameterization results in notable improvements in the simulation of seawater temperature,salinity,and density,with respective reductions in their root mean square errors of 4.36%,19.77%,and 1.84%.
基金Supported by the National Key Research and Development Program of China(2018YFC1505801)National Natural Science Foundation of China(41705059)Startup Fund for Introduced Talents of Nanjing University of Information Science&Technology
文摘The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model performance in simulating the convectively coupled equatorial waves(CCEWs) by comparing the daily output of precipitation from a 23-yr coupled run with the observational precipitation data from Global Precipitation Climatology Project(GPCP). Four dominant modes of CCEWs including the Kelvin, equatorial Rossby(ER), mixed Rossby–gravity(MRG), tropical depression-type(TD-type) waves, and their annual mean and seasonal cycle characteristics are investigated respectively. It is found that the space–time spectrum characteristics of each wave mode represented by tropical averaged precipitation could be very well simulated by CAMS-CSM, including the magnitudes and the equivalent depths. The zonal distribution of wave associated precipitation is also well simulated, with the maximum centers over the Indian Ocean and the Pacific Ocean. However, the meridional distribution of the wave activities is poorly simulated, with the maximum centers shifted from the Northern Hemisphere to the Southern Hemisphere, especially the Kelvin, MRG, and TD waves. The seasonal cycle of each wave mode is generally captured by the model, but their amplitudes over the Southern Hemisphere during boreal winter are grossly overestimated. The reason for the excessive wave activity over the southern Pacific Ocean in the simulation is discussed.
文摘The influence of E1 Nifio-Southern Oscillation （ENSO） on the convectively coupled Kelvin waves over the tropical Pacific is investigated by comparing the Kelvin wave activity in the eastern Pacific （EP） E1 Nifio, central Pacific （CP） E1 Nifio, and La Nifia years, respectively, to 30-yr （1982 2011） mean statistics. The convectively coupled Kelvin waves in this study are represented by the two leading modes of empirical orthogonal function （EOF） of 2-25-day band-pass filtered daily outgoing longwave radiation （OLR）, with the estimated zonal wavenumber of 3 or 4, period of 8 days, and eastward propagating speed of 17 m s-1. The most significant impact of ENSO on the Kelvin wave activity is the intensification of the Kelvin waves during the EP E1 Nifios. The impact of La Nifia on the reduction of the Kelvin wave intensity is relatively weaker, reflecting the nonlinearity of tropical deep convection and the associated Kelvin waves in response to ENSO sea surface temperature （SST） anomalies. The impact of the CP E1 Nifio on the Kelvin waves is less significant due to relatively weaker SST anomalies and smaller spatial coverage. ENSO may also alter the frequency, wavelength, and phase speed of the Kelvin waves. This study demonstrates that low- frequency ENSO SST anomalies modulate high-frequency tropical disturbances, an example of weather- climate linkage.
基金supported by the National Natural Science Foundation of China(Grant No.42305013)Joint Research Project for Meteorological Capacity Improvement(Grant Nos.23NLTSQ002 and 24NLTSQ001)+2 种基金China Meteorological Administration Tornado Key Laboratory(Grant No.TKL202307)the China Meteorological Administration Youth Innovation Team Fund(Grant No.CMA2024QN05)a research project of the Chinese Academy of Meteorological Science(Grant No.2023Z019)。
文摘This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic linkages with Northeast China cold vortices(NCCVs)of tornadic storms under different convective modes.Results reveal that discrete storms account for 70%of events,with clustered cells(CC)being the most frequent mode,while significant tornadoes(EF2+)are primarily associated with isolated cells(IC)and broken lines(BL).The storm mode distribution in northeastern China resembles that of the central United States but with a higher proportion of CC and lower IC.In contrast,southern China exhibits a higher frequency of quasi-linear(QL)modes(>50%),similar to European patterns.Although no single parameter clearly differentiates between all tornado modes,distinct morphological characteristics emerge through specific parameter combinations:NL modes are characterized by high 0-1 km storm-relative helicity(SRH1)and humidity but low 0-6 km shear(SR6),whereas IC modes display contrasting features with low SRH1 and high CAPE.Notably,83%of tornadoes are associated with NCCVs,preferentially forming in southeastern/southwestern quadrants.Strong tornadoes favor southeastern quadrants,while NCCV intensity correlates with tornadic distance from vortex centers.Three characteristic synoptic configurations emerge:(T1)strong deep vortices with vertically aligned cold troughs,generating southeast-dominant tornado clusters characterized by a high proportion of BL and QL modes;(T2)weaker vortices featuring sub-synoptic troughs,with southern-distributed events dominated by a predominance of the CC mode;(T3)transverse-trough systems exhibiting CAPE-SRH decoupling and reduced tornadic activity.This study enhances our understanding of tornadoes in northeastern China,informing future research on formation mechanisms,prediction methods,and disaster prevention strategies.
基金This study was supported by Internal Research Support Programs(Program No.IRSPG202104),Wenzhou-Kean University,China.
文摘The theoretical analysis of the mixed convective Buongiorno nanofluid flow in an inclined annular microchannel with convectively heated walls subjected to the effects of nonlinear thermal radiation,exponential heat source(EHS),thermal dependent heat source(THS)is carried out.The description of the Buongiorno nanofluid is implemented to analyze the Brownian diffusion and thermo-migration mechanisms.The general boundary conditions for the velocity,thermal,and nanoparticle volume fraction(NVF)are considered.Numerical solutions for fully developed governing equations are obtained using bvp5c solver and verified with FEM.The optimization of heat transport rates is made by using the Box-Behnken designbased response surface method.It is found that the Lorentz force and the inclination angle of the annulus significantly affect the rheological characteristics of the nanofluid.Nanoparticles increase thermal energy in the system through Brownian diffusion and thermophoresis,resulting in increased temperature field.Internal heat sources would serve as an important tool for modulating the thermal field in microchannel,as they are directly associated.At low-level values of the thermal Biot number,the exponential heat source,and the thermal radiation parameter,it is possible to attain the maximum Nusselt number on both walls of the annulus.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.52074182,52304406 and U23A20612)the Natural Science Foundation of Shanghai(Grant Nos.22ZR1430700 and 23TS1401900)+1 种基金the National Science and Technology Major Project(No.2017-VII-0008-0102)Neng Ren acknowledges the Startup Fund for Young Faculty at SJTU.
文摘Low-angle grain boundaries(LAGBs)are one of the solidification defects in single-crystal nickel-based superalloys and are detrimental to the mechanical properties.The formation of LAGBs is related to dendrite deformation,while the mechanism has not been fully understood at the mesoscale.In this work,a model coupling dendrite growth,thermal-solutal-fluid flow,thermal stress and flow-induced dendrite deformation via cellular automaton-finite volume method and finite element method is developed to study the formation of LAGBs in single crystal superalloys.Results reveal that the bending of dendrites is primarily attributed to the thermal-solutal convection-induced dendrite deformation.The mechanical stress of dendrite deformation develops and stabilises as solidification proceeds.As the width of the mushy zone gets stable,stresses are built up and then dendritic elastoplastic bending occurs at some thin primary dendrites with the wider inter-dendritic space.There are three characteristic zones of stress distribution along the solidification direction:(i)no stress concentration in the fully solidified regions;(ii)stress developing in the primary dendrite bridging region,and(iii)stress decrease in the inter-dendritic uncontacted zone.The stresses reach maximum near the initial dendrite bridging position.The lower temperature gradients,the finer primary dendritic trunks and sudden reductions in local dendritic trunk radius jointly promote the elastoplastic deformation of the dendrites.Corresponding measures are suggested to reduce LAGBs.
基金supported by the National Natural Science Foundation of China (Grant No.42394122)CAS Project of Stable Support for Youth Team in Basic Research Field (YSRR-018)+1 种基金the National Key R&D Program of China (2023YFC3007703)the Chinese Meridian Project, and the International Partnership Program of Chinese Academy of Sciences (183311KYSB20200003)。
文摘On 19 May 2022, an outbreak of 105 red sprites that occurred over South Asia was fortuitously recorded by two amateurs from a site in the southern Tibetan Plateau(TP), marking the highest number captured over a single thunderstorm in South Asia. Nearly half of these events involved dancing sprites, with an additional 16 uncommon secondary jets and at least four extremely rare green emissions called “ghosts” observed following the associated sprites. Due to the absence of the precise timing needed to identify parent lightning, a method based on satellite motion trajectories and star fields is proposed to infer video frame timestamps within an error of less than one second. After verifying 95 sprites from two videos, our method identified the parent lightning for 66 sprites(~70%). The sprite-producing strokes, mainly of positive polarity with peak currents exceeding +50 k A, occurred in the stratiform region of a mesoscale convective complex(MCC)that spanned the Ganges Plain to the southern TP, with a cloud area over 200 000 km2 and a minimum cloud-top black body temperature near 180 K. This observation confirms that thunderstorms in South Asia, akin to mesoscale convective systems(MCSs) in the Great Plains of the United States or coastal thunderstorms in Europe, can produce numerous sprites,including complex species. Our analysis bears important implications for characterizing thunderstorms above the southern TP and examining their physical and chemical effects on the adjacent regions, as well as the nature of the coupling between the troposphere and middle-upper atmosphere in this region.
基金support of this work by the National Natural Science Foundation of China (Grant Nos.41972316 and 41672252).
文摘The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.
基金Doctoral Research Start-up Fund of Lanzhou University of Arts and Science(2021-9)Innovation Fund for Colleges and Universities of Gansu Province,China(2022B-265)。
文摘The wetting behavior of liquid tin(Sn)solder on copper(Cu)substrate at 250℃was investigated by the wetting balance method under the action of direct current(DC).The curves of wetting balance were measured and the morphology of the intermetallic compound(IMC)precipitated at the interface were observed.Results show that DC has a significant effect on the wettability and IMC.As the current increases,the balance wetting force and the thickness of the IMC layer increase.The direction of the DC also has a certain effect on the balance wetting force and IMC layer.When the current is negative,the final balance wetting force and the thickness of the Cu_(6)Sn_(5) layer are significantly higher than those in the positive current case,which is attributed to electromigration.The IMC precipitation at the interface provides a chemical driving force for the movement of the triple junction.The interaction of the interface atoms and the chemical reaction are enhanced by DC,thereby improving wettability.Meanwhile,the Marangoni convection caused by DC inside liquid Sn solder changes the structure of triple junction,which provides a physical driving force for the spread of the liquid Sn solder on the Cu substrate.
基金Shenzhen Science and Technology Program(JSGG20220831092800001)。
文摘The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.
基金funded by the Ministry of Education of the Russian Federation within the framework of a state assignment,number 1023032300071-6-2.3.1.
文摘Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied.The centrifugal force plays a stabilizing role,while thermal convection is determined by the“thermovibrational mechanism”.Convective flow is excited due to oscillations of a non-isothermal rotating fluid.Thermal vibrational convectionmanifests in the form of two-dimensional vortices elongated along the axis of rotation,which develop in a threshold manner with an increase in the amplitude of fluid oscillations.The objective of the present study is to clarify the nature of another phenomenon,i.e.,three-dimensional convective vortices observed in the experiments both before the excitation of the convection described above and in the supercritical region.The experimental study of the oscillatory and the time-averaged flow fields by particle image velocimetry is accompanied by the theoretical research of inertial waves.It is found that three-dimensional fluid flows owe their origin to inertial waves.This is confirmed by a high degree of agreement between the experimental and theoretical results.Experiments with cavities of different lengths indicate that the vortices are clearly seen in cavities thatmeet the conditions of resonant excitation of inertial modes.Furthermore,the length of the cavity has no effect on heat transfer,which is explained by the comparatively low intensity of the wave-induced flows.The main contribution to heat transfer is due to vortices elongated along the axis of rotation.The novel results are of significant practical importance in various fields.
文摘Understanding the complex interaction between heat and mass transfer in non-Newtonian microflows is essential for the development and optimization of efficient microfluidic and thermal management systems.This study investigates the magnetohydrodynamic(MHD)thermosolutal convection of a Casson fluid within an inclined,porous microchannel subjected to convective boundary conditions.The nonlinear,coupled equations governing momentum,energy,and species transport are solved numerically using the MATLAB bvp4c solver,ensuring high numerical accuracy and stability.To identify the dominant parameters influencing flow behavior and to optimize transport performance,a comprehensive hybrid optimization framework—combining a modified Taguchi design,Grey Relational Analysis(GRA),and Principal Component Analysis(PCA)—is proposed.This integrated strategy enables the simultaneous assessment of skin friction,Nusselt number,and Sherwood number,providing a rigorous multi-objective evaluation of system performance.Comparative validation with benchmark results from the literature confirms the accuracy and reliability of the present formulation and its numerical implementation.The results highlight the intricate coupling among flow slip,buoyancy effects,and convective transport mechanisms.Increased slip flow enhances axial velocity,while a higher solutal Biot number intensifies concentration gradients near the channel walls.Conversely,a lower thermal Biot number diminishes the temperature field,indicating weaker heat transfer across the boundaries.PCA results reveal that the first principal component(PC1)accounts for most of the system variance,demonstrating the dominant influence of coupled flow and transport parameters on overall system performance.
基金Project(52276068)supported by the National Natural Science Foundation of China。
文摘This study examines the intricate occurrences of thermal and solutal Marangoni convection in three-layered flows of viscous fluids,with a particular emphasis on their relevance to renewable energy systems.This research examines the flow of a three-layered viscous fluid,considering the combined influence of heat and solutal buoyancy driven Rayleigh-Bénard convection,as well as thermal and solutal Marangoni convection.The homotopy perturbation method is used to examine and simulate complex fluid flow and transport phenomena,providing important understanding of the fundamental physics and assisting in the optimization of various battery configurations.The inquiry examines the primary elements that influence Marangoni convection and its impact on battery performance,providing insights on possible enhancements in energy storage devices.The findings indicate that the velocity profiles shown graphically exhibit a prominent core zone characterized by the maximum speed,which progressively decreases as it approaches the walls of the channel.This study enhances our comprehension of fluid dynamics and the transmission of heat and mass in intricate systems,which has substantial ramifications for the advancement of sustainable energy solutions.
基金supported by the National Natural Science Foundation of China(Grant No.42305169)the Basic Research Fund of CAMS(Grant No.2023Y001)the National Key Scientific and Technological Infrastructure project“Earth System Numerical Simulation Facility”(Earth Lab)。
文摘Accurately simulating mesoscale convective systems(MCSs)is essential for predicting global precipitation patterns and extreme weather events.Despite the ability of advanced models to reproduce MCS climate statistics,capturing extreme storm cases over complex terrain remains challenging.This study utilizes the Global–Regional Integrated Forecast System(GRIST)with variable resolution to simulate an eastward-propagating MCS event.The impact of three microphysics schemes,including two single-moment schemes(WSM6,Lin)and one double-moment scheme(Morrison),on the model sensitivity of MCS precipitation simulations is investigated.The results demonstrate that while all the schemes capture the spatial distribution and temporal variation of MCS precipitation,the Morrison scheme alleviates overestimated precipitation compared to the Lin and WSM6 schemes.The ascending motion gradually becomes weaker in the Morrison scheme during the MCS movement process.Compared to the runs with convection parameterization,the explicit-convection setup at 3.5-km resolution reduces disparities in atmospheric dynamics due to microphysics sensitivity in terms of vertical motions and horizontal kinetic energy at the high-wavenumber regimes.The explicit-convection setup more accurately captures the propagation of both main and secondary precipitation centers during the MCS development,diminishing the differences in both precipitation intensity and propagation features between the Morrison and two single-moment schemes.These findings underscore the importance of microphysics schemes for global nonhydrostatic modeling at the kilometer scale.The role of explicit convection for reducing model uncertainty is also outlined.
基金Key-Area Research and Development Program of Guangdong (2020B1111200001)National Natural Science Foundation of China (42230105, U2142213, 42175167)。
文摘Taking short-duration heavy rainfall and convective wind gusts as examples, the present study examined the characteristics of radar reflectivity and several convective parameters. We analyzed nowcasting techniques by integrating a high-resolution numerical weather prediction model with these convective parameters. Based on the CMA-GD 1-km model and its assimilation system, we conducted repeated tests on radar reflectivity data assimilation and analyzed their impact on nowcasting accuracy. Based on these analyses, we proposed a method to improve model forecasts using the useful indicative information provided by high-frequency radar reflectivity data and convective parameters. The improved method was applied to the CMA-GD 1-km model for nowcasting tests. Evaluations from batch tests and case analysis show that the proposed method significantly reduced the model's false alarm rates and improved its nowcasting performance.
基金supported by the Ignite National Technology fund,under National Grassroots Initiatives Program of ICT R&D(NIGRI),Project ID.NGIRI-2024-23901 of 2024.
文摘This research focuses on developing innovative hybrid solar dryers that combine solar Photovoltaic(PV)and solar thermal systems for sustainable food preservation in Pakistan,addressing the country’s pressing issues of high post-harvest losses and unreliable energy sources.The proposed active hybrid solar dryer features a drying cabinet,two Direct Current(DC)fans for forced convection,and a resistive heating element powered by a 180 W solar PV panel.An energy-storing battery ensures continuous supply to the auxiliaries during periods of low solar irradiance,poor weather conditions,or nighttime.Tomatoes,a delicate and in-demand crop,were selected for experimentation due to their high perishability.Three experiments were conducted on the same prototype:natural convection direct solar dryer(NCDSD),forced convection direct solar dryer(FCDSD),and forced convection hybrid solar dryer(FCHSD).Each experiment began with 0.2 kg of tomatoes at 94%moisture content,achieving significant reductions:28.57%with NCDSD,16.667%with FCDSD,and 16.667%with FCHSD.The observed drying rates varied:1.161 kg/h for NCDSD,2.062 kg/h for FCDSD,and 2.8642 kg/h for FCHSD.This study presents a comparative analysis of efficiency,drying rate,and cost-effectiveness,alongside the system’s economic and environmental feasibility.
