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When constructing solar aerobaric power plants, it is necessary to develop effective ways to accelerate convective flows initiated by the action of a high-temperature working fluid heated due to the concentration of solar radiation, accumulation of dissipated heat losses and the use of the greenhouse effect. As an option for organizing the flow in the aerodynamic module of the solar aerobaric power plants, article considered a diagram of the cyclotron acceleration of the flow during horizontal and vertical transfer of convective air currents formed in cells containing alternately located cold and hot side boundaries and differently heated upper and lower bases.

Atmospheric turbulence is an intrinsic factor that causes uncertainty of wind speed and its power generation by wind turbine. The research of atmospheric turbulence characteristics of wind farms can be used to reduce this uncertainty. In this paper, enough measurement data getting from actual wind farms is used for information processing to quantitatively analyze the daily variation of wind speed and its power output characteristics. Furthermore, the concept of spatiotemporal diurnal modulation characteristics of atmospheric turbulence is proposed with a global scope, which is an intrinsic property of wind. Besides the daily variation characteristics, the average hourly wind speed has a short-term modulation effect on its turbulence and provides a modulation characteristic on wind speed uncertainty. Moreover, the long-term modulation process is affected by seasonal and regional factors, indicating that it has spatiotemporal characteristics. This atmospheric turbulence characteristic has similar effects on characteristic description parameters. However, the characteristics description parameters of wind speed and wind power variation fail to reflect such intrinsic characteristics that are not affected by the spatiotemporal diurnal modulation characteristics of atmospheric turbulence. This indicates that they do not have diurnal characteristics. Finally, a time-varying model combined with the spatiotemporal diurnal modulation characteristics of wind speed and its power generation is discussed by applying on the evaluation of frequency control in power systems. It is shown that the results obtained by measured data processing could improve the power generation quality of large-scale wind power effectively.

Climate models are the primary tools for investigating the response of the climate system to various forcings and for climate predictions. The combined use of the data from remote sensors and meteostations allows taking into account the spatial and temporal components of monitoring. In this study the temperature forecasting technique was improved by using the data from thermal imaging satellites and weather stations. This technique uses for this purpose the model of dependence of temperature received from satellite imagery on the temperature obtained from existing meteorological stations. During the investigation of the variables selected from the input data array, it was shown that satellite imagery data can be used in regional models of temperature prediction, and temperature traces obtained from satellite imagery and weather stations at similar points show similar dynamics. The effectiveness of the group method of data handling using multi-row algorithm for forecasting temperature for areas with no meteorological stations is shown.

The simulations of the monsoon intraseasonal oscillation (MISO) during the Indian summer monsoon (ISM) are evaluated with 19 atmosphere–ocean coupled general circulation models (CGCMs) from phase 6 of the Coupled Model Inter-comparison Project (CMIP6). The focus is on the northward propagation of MISO. The CMIP6 models have great improvement in simulating the mean rainfall, as 17 out of 19 models can reasonably simulate the mean rainfall. However, many models fail to reproduce the realistic patterns of the mean rainfall and the MISO amplitude, particularly over land in the monsoon region. The underestimation of the MISO amplitude is still a notable model bias in CMIP6. Moreover, 9 out of 19 models cannot generate realistic northward propagation features, and some even reproduce a stationary MISO pattern. Process diagnostics based on the seasonal mean vertical zonal wind shear, low-level mean moisture, and vortex tilting are also examined. It is found that the accuracy of model simulations of vortex tilting is strongly associated with the northward propagation of MISO. In contrast, the model fidelity in MISO is not dependent on the simulation skill for the seasonal mean state. In addition, decomposition analysis of vortex tilting illustrates that the meridional shear of the intraseasonal vertical velocity is crucial to the tilting simulation. The poor model fidelity in vortex tiling is caused by the weak convection, particularly the absence of downdraft to the north of the convection center. The coupling between the moisture in the boundary layer and the tilting in the free troposphere may be responsible for capturing the vertical motions. In summary, vortex tilting can be a useful metric for evaluating the northward propagation of MISO.

Since climate change has altered extreme precipitation and temperature patterns, further study of these patterns is essential. The examination of precipitation and temperature patterns is of great significance to water engineers, water resources management, and hydrological studies. Accordingly, this study explored the nonlinear dynamic patterns and their sources governing extreme precipitation and temperatures using multifractal, shuffling, surrogating techniques, and extreme climate indices. The temperature and precipitation data regarding central England (1931–2019) were collected and used for analysis. The results of extreme climate indices demonstrated climate change in the study area. Besides, the multifractal analysis indicated that all indices’ time series were characterized by multifractality. Despite the fact that multifractality of the maximum 1-day precipitation, minimum of maximum temperature, and maximum of maximum temperature was predominantly produced by correlation properties (long-range correlations between small and large local fluctuations), the multifractal characteristics of the warm nights were due to a probability density function (PDF) predominance. Moreover, multifractal properties of the diurnal temperature range, maximum 5-day precipitation, maximum of minimum temperature, minimum of minimum temperature, cool nights, and cool and warm days were produced by the identical extent of correlation properties and the PDF.

Abstract A phenomenon of ice rings in Lake Baikal is considered. A hydrodynamic theory is proposed according to which geostrophic vortices form under ice in the area near the ice rings. These vortices are due to bed relief, namely, underwater canyons; therefore, they are referred to as canyon vortices. It is shown that a divergent ring vortex forms under ice in the ring domain at the crossing of a vertical cylindrical Stewartson layer on the lateral surface of the canyon geostrophic vortex and under-ice horizontal Ekman layer in the form of a horizontal vortex torus, and the melting of ice below in the form of a ring is due to the formation of this vortex torus.

We study the classical result by Bruijn and Erdős regarding the bound on the number of lines determined by a n-point configuration in the plane, and in the light of the recently proven Tropical Sylvester-Gallai theorem, come up with a tropical version of the above-mentioned result. In this work, we introduce stable tropical lines, which help in answering questions pertaining to incidence geometry in the tropical plane. Projective duality in the tropical plane helps in translating the question for stable lines to stable intersections that have been previously studied in depth. Invoking duality between Newton subdivisions and line arrangements, we are able to classify stable intersections with shapes of cells in subdivisions, and this ultimately helps us in coming up with a bound. In this process, we also encounter various unique properties of linear Newton subdivisions which are dual to tropical line arrangements.

It is shown that for the design of buildings and individual rooms with normative concentrations of light air ions of both polarities, a preliminary estimated assessment of the dynamics of this indicator in space and time is appropriate. In the general case, it is possible to use the continuity equation for weakly ionized plasma for one direction. This is due to the low concentration of air ions in the air. The ratio of molecular kinetic theory of gases is used to determine the necessary indicators - the average lifetime of air ions, free path length. To determine the average speed - Maxwell's distribution. It is shown that the propagation of air ions due to diffusion processes is insignificant, and the corresponding calculations have large errors. Calculations on the propagation of air ions by directed air movement from the source of artificial ionization are given. The distribution of air ion concentrations can be most accurately calculated taking into account their recombination, deposition on heavy air ions and neutral suspended parts (fine dust and aerosols). Relevant coefficients are mostly issued from reference sources. If there are electrostatic fields in the premises, generated due to the triboelectric effect and other factors, it is necessary to take into account the deposition of air ions on these surfaces. In order to correctly determine the concentrations of air ions, in addition to the values of the mobility of negative and positive air ions, data on electrostatic field strengths are required. The values of such fields are unpredictable, so they are measured by appropriate instruments in similar conditions. Verification of calculated data using electrostatic charge meters and air ion counter proved the reasonable convergence of expected and actual data. It is advisable to develop two- and three-dimensional models of the propagation of air ions of both polarities in rooms of different purposes, configurations of equipment placement, the presence of artificial ionization sources and directional air movement.

We have examined variations in electron density Ne at ionospheric F1-layer heights during geomagnetic storms at the Irkutsk ionospheric station (52° N, 104° E). We have selected geomagnetic storms of varying intensity as well as quiet days for each event for the winter and summer seasons of 2003. We have analyzed the electron density in the daytime during geomagnetic storms at 150–190 km heights. Different effects of geomagnetic storms on Ne in different seasons at these heights were found. There is a slight change in the electron density during summer geomagnetic storms. On the other hand, there is an interesting effect in winter indicating the summer-winter asymmetry of the Ne response to the geomagnetic storms at these heights in 2003: in winter there is a significant influence of disturbances on Ne at a height of 190 km and a smaller effect at lower heights.

The article is devoted to decision of actual task of air distribution efficiency increase due to swirled air jets application. The aim of the paper is investigation of swirled air jets, analytical dependencies obtaining for determination of the air velocity attenuation coefficient, aerodynamic local resistance coefficient and noise level from the twisting plates inclination angle; optimization of the twisting plates inclination angle of the air distributor. It has been established that increase of the angle results in the air velocity attenuation coefficient increase and results in decrease of the noise level and resistance coefficient of air distributor. The optimum angle of the plates is determined considering aerodynamic, noise and energy aspects and equals 36°.

The electro-impulse de-icing system (EIDI) is a mechanical de-icing system that guarantees the safe flight of the aircraft under icing weather conditions. It owns many merits such as high reliability and low energy consumption. To solve the problem of the small de-icing area under single-channel, a dual-channel EIDI system model is proposed. The electro-magnetic field and de-icing results of the dual-channel EIDI system are investigated. Comparisons of de-icing results between simulations and experiments on the flat aluminum plate are also made. Furthermore, the de-icing research is carried out with a real wing structure by varying the excitation time and magnitude of impulse load. Simulation results of the electro-magnetic field show that the maximum of the density of electro-magnetic force always appears at the midpoint of the inner and outer radius of coils. The excitation of the two coils is independent and can be decoupled. The de-icing results illustrate that the de-icing rate increases with the striking intervals and impulse load. The load multiple (LM) should be selected between 1.5 and 3 for the dual-channel EIDI system for energy optimization. In addition, it is advisable to distribute the impulse loads with the largest possible difference on both sides when the LM is 1–3.

The upper-ocean processes controlling the near-surface layer temperature in the western Gulf of Mexico (GOM) are examined by estimating the contributing terms in the heat equation based on a 54-year simulation of an eddy-resolving HYbrid Coordinate Ocean Model (HYCOM). An eddy-active region defined by large surface eddy kinetic energy, representing the Loop Current eddies (LCEs) primary trajectory region, is selected for analysis. Both observations and the simulation reveal that the mean net surface heat flux cools the northern GOM and warms the southern GOM. Mean horizontal heat advection contributes to an overall cooling in the eddy-active region. Mean vertical heat advection has a strong seasonal variability associated with the strong seasonal cycle of the mixed layer process: winters tend to have a strong downward heat advection in the eddy-active region and a strong upward heat advection in the rest of the western GOM, while summers tend to have a weak advective heat flux. The downwelling (upwelling) is primarily due to the dominant anticyclonic (cyclonic) wind stress curl. Mean eddy heat flux convergence contributes to the overall warming in the upper ocean of the western GOM. Diffusive flux is not small across the thermocline, and it is expected to have an insignificant influence on the near-surface temperature.

The torus is a promisingly potential alternative to traditionally cylindrical pressure vessels due to its capability to store more hydrogen energy within limited space. Constant angle winding is widely used in practical filament winding. Hence, it is necessary to study constant angle winding on the torus. This paper presents constant winding angle curve on torus, a new winding trajectory, and gives a sufficient and necessary condition that makes it nonslip and non-bridging, and a computational formula for determining the lower bound of the winding angle of stable constant winding angle curve. By combining with semi-geodesics, we propose an integration design method for winding pattern and develop a computer aided path design system for filament winding torus, which can design constant angle winding pattern or approximate equilibrium winding for toroidal composite pressure vessels. Since our approach uses constant winding angle curve and integration trajectories besides semi-geodesics, our method has more design space for optimizing fiber path, and outperforms the existing methods.

Considering the transient heat and mass transfer process of the impinged water droplets during aircraft icing, an unsteady thermodynamic model was established to simulate the dynamic developments of the water film and the ice layer on aircraft surfaces. The unsteady model was discretized in an implicit scheme with a corresponding solution method. Icing simulations were performed for a NACA0012 airfoil, and the results show acceptable agreement with the data in the literature. Water film first appears near the stagnation point, and then, the film thickness increases, and the runback water region expands with time, affecting the icing rate, the surface temperature, and the ice type. The development of the water film is rapid, and the thickness and range of the film, along with the icing rate, reach a steady state in a short time. The stable characteristics obtained by the unsteady model are consistent with those of the Messinger steady model. Despite that the unsteady and steady models can obtain similar ice shapes in icing simulations, the dynamic developments of the water film and the ice layer should be considered at the initial stage of ice accretion or in the short-time icing simulations.

This article describes the implementation of a coupling between a global forecast model (CFSv2.0) and a wave model (WW3) and investigates the effects of ocean surface waves on the air–sea interface in the new framework. Several major wave-related processes, including the Langmuir mixing, the Stokes–Coriolis force with entrainment, air–sea fluxes modified by the Stokes drift, and momentum roughness length, are evaluated in two groups of 56 d experiments, one for boreal winter and the other for boreal summer. Comparisons are made against in situ buoys, satellite measurements, and reanalysis data to evaluate the influence of waves on intraseasonal prediction of sea surface temperature (SST), 2 m air temperature (T02), mixed layer depth (MLD), 10 m wind speed (WSP10), and significant wave height (SWH). The wave-coupled experiments show that overestimated SSTs and T02s, as well as underestimated MLDs at mid-to-high latitudes in summer from original CFSv2.0, are significantly improved due to enhanced vertical mixing generated by the Stokes drift. For WSP10s and SWHs, the wave-related processes generally reduce biases in regions where WSP10s and SWHs are overestimated. On the one hand, the decreased SSTs stabilize the marine atmospheric boundary layer and weaken WSP10s and then SWHs. On the other hand, the increased roughness length due to waves reduces the originally overestimated WSP10s and SWHs. In addition, the effects of the Stokes drift and current on air–sea fluxes also rectify WSP10s and SWHs. These cases are helpful for the future development of the two-way CFSv2.0–wave coupled system.

A microscale wildfire model, QES-Fire, that dynamically couples the fire front to microscale winds was developed using a simplified physics rate of spread (ROS) model, a kinematic plume-rise model and a mass-consistent wind solver. The model is three-dimensional and couples fire heat fluxes to the wind field while being more computationally efficient than other coupled models. The plume-rise model calculates a potential velocity field scaled by the ROS model’s fire heat flux. Distinct plumes are merged using a multiscale plume-merging methodology that can efficiently represent complex fire fronts. The plume velocity is then superimposed on the ambient winds and the wind solver enforces conservation of mass on the combined field, which is then fed into the ROS model and iterated on until convergence. QES-Fire’s ability to represent plume rise is evaluated by comparing its results with those from an atmospheric large-eddy simulation (LES) model. Additionally, the model is compared with data from the FireFlux II field experiment. QES-Fire agrees well with both the LES and field experiment data, with domain-integrated buoyancy fluxes differing by less than 17% between LES and QES-Fire and less than a 10% difference in the ROS between QES-Fire and FireFlux II data.

Based on a system of parabolic equations describing the process of conversion of coke ash residue in an oxygen-enriched vapor-air mixture, a non-stationary model of solid fuel gasification in a fixed layer is built. This model takes into account an interphase convective heat transfer, radiation-conductive heat transfer of the solid phase, radiant and conductive heat exchange of the layer with the reactor wall, heterogeneous and homogeneous chemical reactions, gravity forces and aerodynamic drag. The proposed model allows to obtain detailed information about the geometric, aerodynamic, thermal and physicochemical parameters of gasification of solid fuel in a fixed bed at different pressures at any time. Bibl. 7, Fig. 1.

Based on the measurements conducted over the landfast sea ice in Prydz Bay, East Antarctica during the sea-ice growth season in 2016, various parameterization schemes in the high-resolution thermodynamic snow/ice model HIGHTSI are evaluated. The parameterization scheme of turbulent fluxes produces the largest errors compared with the parameterization schemes for other surface heat fluxes. However, the sea-ice thickness simulation is most sensitive to the differences in upward longwave radiation at the surface. In addition, the sea-ice thickness simulation during the growth season is highly sensitive to the oceanic heat flux, and a new oceanic heat flux parameterization scheme based on the bulk method is proposed. The new parameterization scheme is tested in a second year, and it significantly improves the model performance relative to the standard configuration when compared against observations. Finally, the seasonal variation in the heat budget and its influence on the sea-ice thickness variation are analyzed. The net shortwave radiation, sensible heat flux and conductive heat flux (the net longwave radiation and latent heat flux) are found to be the surface heat sources (heat sinks) during the growth season. The larger conductive heat flux and the smaller oceanic heat flux can intensify the growth of sea ice.

Inferring the climate and surface conditions of terrestrial exoplanets in the habitable zone is a major goal for the field of exoplanet science. This pursuit will require both statistical analyses of the population of habitable planets as well as in-depth analyses of the climates of individual planets. Given the close relationship between habitability and surface liquid water, it is important to ask whether the fraction of a planet's surface where water can be a liquid, $\chi_\text{hab}$, can be inferred from observations. We have produced a diverse bank of 1,874 3D climate models and computed the full-phase reflectance and emission spectrum for each model to investigate whether surface climate inference is feasible with high-quality direct imaging or secondary eclipse spectroscopy. These models represent the outcome of approximately 200,000 total simulated years of climate and over 50,000 CPU-hours, and the roughly-100 GB model bank and its associated spectra are being made publicly-available for community use. We find that there are correlations between spectra and $\chi_\text{hab}$ that will permit statistical approaches. However, spectral degeneracies in the climate observables produced by our model bank indicate that inference of individual climates is likely to be model-dependent, and inference will likely be impossible without exhaustive explorations of the climate parameter space. The diversity of potential climates on habitable planets therefore poses fundamental challenges to remote sensing efforts targeting exo-Earths., Comment: 12 pages, 6 figures, 1 table. Revised and accepted for publication in MNRAS

Given the climatic importance of the Madden–Julian oscillation (MJO), this study evaluates the capability of CMIP6 models in simulating MJO eastward propagation in comparison with their CMIP5 counterparts. To understand the representation of MJO simulation in models, a set of diagnostics with respect to MJO-associated dynamic and thermodynamic structures is applied, including large-scale zonal circulation, vertical structures of diabatic heating and equivalent potential temperature, moisture convergence at the planetary boundary layer (PBL), and the east–west asymmetry of moisture tendency relative to the MJO convection. The simulated propagation of the MJO in CMIP6 models shows an overall improvement in realistic speed and longer distance, which displays a robust linear regression relationship against the above-mentioned dynamic and thermodynamic structures. The improved MJO propagation in CMIP6 largely benefits from better representation of premoistening processes that is primarily contributed by improved PBL moisture convergence. In addition, the convergence of moisture and meridional advection of moisture prior to the MJO convection are enhanced in CMIP6, while the zonal advection of moisture is as weak as that in CMIP5. The increased convergence of moisture is a result of enhanced lower-tropospheric moisture and divergence, and the enhanced meridional advection of moisture can be caused by sharpened meridional gradient of mean lower-tropospheric moisture in the western Pacific. Further examination of the lower-tropospheric moisture budget reveals that the enhanced zonal asymmetry of the moisture tendency in CMIP6 is driven by the drying process to the west of the MJO convection, which is attributed to the negative vertical and zonal advections of moisture.

Large meridional excursions of a jet stream are conducive to blocking and related midlatitude weather extremes, yet the physical mechanism of jet meandering is not well understood. This paper examines the mechanisms of jet meandering in boreal winter through the lens of a potential vorticity (PV)-like tracer advected by reanalysis winds in an advection–diffusion model. As the geometric structure of the tracer displays a compact relationship with PV in observations and permits a linear mapping from tracer to PV at each latitude, jet meandering can be understood by the geometric structure of tracer field that is only a function of prescribed advecting velocities. This one-way dependence of tracer field on advecting velocities provides a new modeling framework to quantify the effects of time mean flow versus transient eddies on the spatiotemporal variability of jet meandering. It is shown that the mapped tracer wave activity resembles the observed spatial pattern and magnitude of PV wave activity for the winter climatology, interannual variability, and blocking-like wave events. The anomalous increase in tracer wave activity for the composite over interannual variability or blocking-like wave events is attributed to weakened composite mean winds, indicating that the low-frequency winds are the leading factor for the overall distributions of wave activity. It is also found that the tracer model underestimates extreme wave activity, likely due to the lack of feedback mechanisms. The implications for the mechanisms of jet meandering in a changing climate are also discussed.

Realistic representation of rainfall characteristics on local scales by state-of-the-art climate models remains a key challenge, especially on sub-daily timescales. In this study, the convection-permitting Weather Research and Forecasting (WRF) model configured with 1.5 km grid spacing is used to simulate precipitation on sub-daily timescales over the Yangtze River Delta Region of China for continuous 10 years (2005–2014). The simulations are compared with rain gauge observations, reanalysis data, and the simulations of a lower resolution WRF with 9 km grid spacing that has a parameterization of convection. The results show that precipitation over the region can be well captured by using the convection-permitting model (CPM). Furthermore, the intensity, duration and coverage of these precipitation events can be more accurately described by the CPM. On the convection timescales of 1–4 h, especially for heavy rainfall events, the CPM is more accurate than the convection-parameterized model in capturing the short-duration events, which may be due to its better account of physical processes related to the convection on the convection-permitting scale. In addition, the extreme events which are more localized and with short-duration can be represented better by the CPM while the convection-parameterized model tends to produce widespread precipitation events covering more grid cells than observations Biases of the simulation by the 9-km mesh convection-parameterized mode appear to be related to the deficiencies in the representation of convections.

Suppression of climate change due to the emission of carbon dioxide is an important target of SDGs. To realize net-zero emission of CO2, the power industry has been tackling the issue with the use of sustainable energies and gas-fired generation based on chemicals that emit no carbon dioxide. The typical sustainable energies are solar cell, wind generation, geothermal generation, and biomass generation. Hydrogen and ammonia are thought to be promising gas without the production of CO2. The current situation of these energies is reviewed here.

The emergence of flexible AC transmission technology provides a new technical means for ensuring the reliable grid connection and stable operation of wind farms. Among them, the static reactive power generator has a fast response speed, which can accurately compensate for the reactive power of the wind farm and improve the power factor; this is widely used in wind farms. To obtain accurate static var generator (SVG) parameters to meet the reliability requirements of a power system, we propose an adaptive estimation method that considers the wind speed fluctuation of wind farms. First, analyzing the dynamic SVG characteristics allowed us to establish a mathematical model. Then, the corresponding relationship between the sensitivity values of the parameters to be identified and the fluctuating wind speed was established, and low and high wind speed models were constructed. Finally, for accurate estimation considering wind speed fluctuation, the parameter initial values are obtained by combining the low wind speed and high wind speed model identification parameters, and we introduce the multimode hybrid estimation of the SVG parameters, providing a new method for accurately identifying the SVG model parameters. The simulation results of the parameter estimation demonstrate the accuracy and stability of the proposed method.

Aerosol viscosity is determined by mixture composition and temperature, with a key influence from relative humidity (RH) in modulating aerosol water content. Aerosol particles frequently contain mixtures of water, organic compounds, and inorganic ions, so we have extended the thermodynamics-based group-contribution model AIOMFAC-VISC to predict viscosity for aqueous electrolyte solutions and aqueous organic–inorganic mixtures. For aqueous electrolyte solutions, our new, semi-empirical approach uses a physical expression based on Eyring's absolute rate theory, and we define activation energy for viscous flow as a function of temperature, ion activities, and ionic strength. The AIOMFAC-VISC electrolyte model's ion-specific expressions were simultaneously fitted, which arguably makes this approach more predictive than that of other models. This also enables viscosity calculations for aqueous solutions containing an arbitrary number of cation and anion species, including mixtures that have never been studied experimentally. These predictions achieve an excellent level of accuracy while also providing physically meaningful extrapolations to extremely high electrolyte concentrations, which is essential in the context of microscopic aqueous atmospheric aerosols. For organic–inorganic mixtures, multiple mixing approaches were tested to couple the AIOMFAC-VISC electrolyte model with its existing aqueous organic model. We discuss the best-performing mixing models implemented in AIOMFAC-VISC for reproducing viscosity measurements of aerosol surrogate systems. We present advantages and drawbacks of different model design choices and associated computational costs of these methods, of importance for use of AIOMFAC-VISC in dynamic simulations. Finally, we demonstrate the capabilities of AIOMFAC-VISC predictions for phase-separated organic–inorganic particles equilibrated to observed temperature and relative humidity conditions from atmospheric balloon soundings. The predictions for the studied cases suggest liquid-like viscosities for an aqueous electrolyte-rich particle phase throughout the troposphere, yet a highly viscous or glassy organic-rich phase in the middle and upper troposphere.

Water jet-guided laser machining is a new compound machining technology, which has been widely used in many fields due to its better processing effect. In this technology, the coupling of laser beam and micro-water jet directly determines the machining effect, and the prerequisite for successful coupling is the steady flow of the water jet, so ensuring the stability of the micro-water jet is the key to the stable machining of water jet-guided laser. Therefore, it is of great significance to studying the stability of the water fiber-optic in water jet-guided laser processing. In this paper, aiming at the problem that the stability of the water fiber-optic is difficult to control, a finite element model of the water fiber-optic is established. The convection model is vortex gas-phase flow “enveloped” water fiber-optic which is used to explain the interaction mechanism, and the flow field distribution of gas-phase flow and water fiber-optic convection was obtained. The results show that water fiber-optic is refined under the constraint of gas-phase flow, and the maximum processing distance can increase by three times. At the same time, the gas-phase flow can accelerate the removal of processing debris, and the processing accuracy and efficiency are improved.

Inaccurate representations of iceberg calving from ice shelves are a large source of uncertainty in mass-loss projections from the Antarctic ice sheet. Here, we address this limitation by implementing and testing a continuum damage-mechanics model in a continental scale ice-sheet model. The damage-mechanics formulation, based on a linear stability analysis and subsequent long-wavelength approximation of crevasses that evolve in a viscous medium, links damage evolution to climate forcing and the large-scale stresses within an ice shelf. We incorporate this model into the BISICLES ice-sheet model and test it by applying it to idealized (1) ice tongues, for which we present analytical solutions and (2) buttressed ice-shelf geometries. Our simulations show that the model reproduces the large disparity in lengths of ice shelves with geometries and melt rates broadly similar to those of four Antarctic ice shelves: Erebus Glacier Tongue (length ~ 13 km), the unembayed portion of Drygalski Ice Tongue (~ 65 km), the Amery Ice Shelf (~ 350 km) and the Ross Ice Shelf (~ 500 km). These results demonstrate that our simple continuum model holds promise for constraining realistic ice-shelf extents in large-scale ice-sheet models in a computationally tractable manner.

Wind energy, a highly popular renewable clean energy, has been increasingly valued by the international community and been leaping forward. However, the original wind speed signal characterized by intermittent fluctuations impose heavy burdens on wind speed forecasting of wind farms. This study proposed a wind speed forecasting method by complying with a model integrating the Variational Mode Decomposition (VMD) and the Improved Multi-Objective Dragonfly Optimization Algorithm (IMODA). First, the VMD was adopted to decompose the original wind speed signal, as an attempt to obtain multiple sub-sequences (IMFs) exhibiting stable frequency domain. Second, to simplify the calculation, the sample entropy (SE) was adopted for the sequence recombination, and the respective recombined sub-sequence of the wind speed was forecasted by using four advanced neural networks. Lastly, the IMODA algorithm was adopted to fuse the forecasting results of the neural network, and the results of the optimal wind speed were forecasted. To verify the effectiveness and adaptability of the algorithm, the wind farm data in four different regions were forecasted. As indicated from the results, this algorithm could outperform other algorithms in the comprehensive forecasting accuracy and the model calculation time, and it could be effectively applied for the wind speed forecasting in wind farms.

Majority of spacecrafts rely on solar power as the main source of energy. The search for a lightweight and cost-efficient energy source with high power conversion efficiency (PCE) led to the development of organic-inorganic metal halide Perovskite solar cells (PSCs). In this paper, the performance of PSCs with different hole-transport material (HTM) prepared for in-orbit demonstration mission onboard CubeSats are compared under simulated space environment such as thermal cycling stress, high-vacuum, UV radiation and vibration. Results show that even though organic and inorganic HTM display superior initial PCE, Carbon HTM PSCs trumps them in terms of stability and is more practical for use in space. The paper also discusses the satellite mission and developed hardware for the first demonstration of Perovskite solar cells on-board a satellite to gather in-orbit information on the performance of Perovskite solar cells in low-earth orbit and how the ground test results would be verified.

Operator ∇ inner products on both sides of Combination of Boyles’ law and Chares law (“B-C law” in short), we got the “Wind Speed Equation of a Point in Air” (“Wind Speed Equation” in short). It suits for describing straight-line motion, and It states that mu ̇ is in proportion to ∇•T. Operator ∇ outer products on both sides of “Wind Speed Equation” (where T is replaced by T), we get the “Rotation Equation of a Point in Air” (“Rotation Equation” in short). It is a vector partial differential equation (PDE), suits for describing circular motion. It states that (mu ̇ ) is in proportion to T. Its solution is found by the method of separating variables. The existence of vector T is proved by the existence of rotation in the atmosphere and the solution of the “Rotation Equation”. It reveals that the vector form of B-C law holds in rotating air. Examples of up-side-down vertical rotation and horizontal rotation are given.

This paper investigates the applicability of two approaches (similarity theory and Dalton’s law) in predicting the evaporation rate. The results of this study showed that conventional Dalton’s based models could not be used to predict the evaporation rate at all convection regimes. Thus, a new formula as a function of vapor density difference was developed to predict evaporation rate at natural turbulent convection. However, still, it cannot get an acceptable result. Also, another two formulas were developed to predict the evaporation rate at forced and mixed convection regimes after considering the nonlinear relationship between the evaporation rate and the vapor pressure difference. The evaporation rate is proportional to the exponent ( n) of the partial vapor pressure difference. This exponent was written as a function of the higher-order polynomial of air velocity to get a good match between experimental results and predicted value, and satisfactory results were achieved. Similarity theory is an analogy between heat and mass transfer methods used to predict the evaporation rate from the still free water surface. The results show that the evaporation rate obtained from the similarity method is much larger than the actual evaporation rate. The similarity theory considers the effect of the vapor density difference. Thus, it can be observed that the experimental results and similarity method results are in good agreement at natural turbulent convection. It is noteworthy that the similarity theory cannot predict the evaporation rate from the still water surface at forced convection. In this convection regime, the evaporated water surface is not completely smooth, which violates the assumption of the similarity theory. A nonlinear regression analysis was conducted to evaluate the empirical correlation of the Sherwood number for mixed convection under turbulent conditions with the exponent n as a logarithmic function of the ratio [Formula: see text], then derived a new formula that can be used to evaluate evaporation rate at mixed convection regime, and the results are in good agreement with the experimental results. The laboratory measurements are made using the large wave tank-wind tunnel combination to control wind speed.

The article considers proposed methodological and technical solutions aimed at improving the accuracy of dropping cargo from aircraft by taking into account the wind speed. The characteristics of lidars of different types, capable of measuring the wind speed both near the aircraft and near the Earth's surface, are discussed. The results of experiments on measuring the wind speed profile at low altitudes in the airfield area are presented. The results of modeling the trajectory of an uncontrollable load falling in wind conditions show that taking into account the wind speed significantly increases the drop accuracy. The cargo was modeled as a sphere of a specified mass with specified aerodynamic coefficients. The effect of the completeness of information about the distribution of wind speed over height on the drop accuracy is shown. In particular, options are compared when the wind speed is measured near the aircraft and near the surface of the earth. The drop accuracy indicators obtained in the course of simulation are given

In theoretical models of tropical dynamics, the effects of both surface friction and upward wave radiation through interaction with the stratosphere are oft-ignored, as they greatly complicate mathematical analysis. In this study, we relax the rigid-lid assumption and impose surface drag, which allows the barotropic mode to be excited in equatorial waves. In particular, a previously developed set of linear, strict quasi-equilibrium tropospheric equations is coupled with a dry, passive stratosphere, and surface drag is added to the troposphere momentum equations. Theoretical and numerical model analysis is performed on the model in the limits of an inviscid surface coupled to a stratosphere, as well as a frictional surface under a rigid lid. This study confirms and extends previous research that shows the presence of a stratosphere strongly shifts the growth rates of fast-propagating equatorial waves to larger scales, reddening the equatorial power spectrum. The growth rates of modes that are slowly propagating and highly interactive with cloud radiation are shown to be negligibly affected by the presence of a stratosphere. Surface friction in this model framework acts as purely a damping mechanism and couples the baroclinic mode to the barotropic mode, increasing the poleward extent of the equatorial waves. Numerical solutions of the coupled troposphere–stratosphere model with surface friction show that the stratosphere stratification controls the extent of tropospheric trapping of the barotropic mode, and thus the poleward extent of the wave. The superposition of phase-shifted barotropic and first baroclinic modes is also shown to lead to an eastward vertical tilt in the dynamical fields of Kelvin wave–like modes.

Gravity wave (GW) momentum and energy deposition are large components of the momentum and heat budgets of the stratosphere and mesosphere, affecting predictability across scales. Since weather and climate models cannot resolve the entire GW spectrum, GW parameterizations are required. Tuning these parameterizations is time-consuming and must be repeated whenever model configurations are changed. We introduce a self-tuning approach, called GW parameter retrieval (GWPR), applied when the model is coupled to a data assimilation (DA) system. A key component of GWPR is a linearized model of the sensitivity of model wind and temperature to the GW parameters, which is calculated using an ensemble of nonlinear forecasts with perturbed parameters. GWPR calculates optimal parameters using an adaptive grid search that reduces DA analysis increments via a cost-function minimization. We test GWPR within the Navy Global Environmental Model (NAVGEM) using three latitude-dependent GW parameters: peak momentum flux, phase-speed width of the Gaussian source spectrum, and phase-speed weighting relative to the source-level wind. Compared to a baseline experiment with fixed parameters, GWPR reduces analysis increments and improves 5-day mesospheric forecasts. Relative to the baseline, retrieved parameters reveal enhanced source-level fluxes and westward shift of the wave spectrum in the winter extratropics, which we relate to seasonal variations in frontogenesis. The GWPR reduces stratospheric increments near 60°S during austral winter, compensating for excessive baseline nonorographic GW drag. Tropical sensitivity is weaker due to significant absorption of GW in the stratosphere, resulting in less confidence in tropical GWPR values.

Commonly used parameterization of mixed layer instabilities in general circulation models was developed for temperate oceans and does not take into account the presence of sea ice in any way. However, the ice–ocean drag provides a strong mechanical coupling between the sea ice and the surface ocean currents and hence may affect mixed layer restratification processes. Here we use idealized simulations of mixed layer instabilities to demonstrate that the sea ice dramatically suppresses the eddy-driven overturning in the mixed layer by dissipating the eddy kinetic energy generated during instabilities. Considering the commonly used viscous-plastic sea ice rheology, we developed an improvement to the existing mixed layer overturning parameterization, making it explicitly dependent on sea ice concentration. Below the critical sea ice concentration of about 0.68, the internal sea ice stresses are very weak and the conventional parameterization holds. At higher concentrations, the sea ice cover starts acting as a nearly immobile surface lid, inducing strong dissipation of submesoscale eddies and reducing the intensity of the restratification streamfunction up to a factor of 4 for a fully ice-covered ocean. Our findings suggest that climate projection models might be exaggerating the restratification processes under sea ice, which could contribute to biases in mixed layer depth, salinity, ice–ocean heat fluxes, and sea ice cover.

A linear Ekman model in the stratified atmospheric boundary layer (ABL) is proposed based on the steady-state version of the linearized three-dimensional primitive equations with the inclusion of the vertical diffusivity. Due to the inclusion of the potential temperature equation and hydrostatic equation, pressure and potential temperature couple with wind in the proposed model, and thus are not arbitrarily specified variables as in previous studies on the baroclinicity in the Ekman model. The extended thermal wind balance equation and the Ekman potential vorticity equation are derived to describe the coupling. The two equations, along with the equation describing the constraint on potential temperature, are employed to derive the analytical solutions of the proposed Ekman model. Because potential temperature is not a specified variable but part of the solution, the derived analytical solutions have very different forms from those derived in previous studies. The differences illustrate the impact of the inclusion of the potential temperature equation and hydrostatic equation on wind, pressure, and potential temperature in the proposed Ekman model. It is found that the computed wind profiles based on the proposed model can capture some important features of the observed wind profiles.

This paper utilizes computer simulations to physical science and applications. High-temperature plasmas and macromolecules are reviewed first including magnetic reconnection in space and DNA translocation of the human body. The second topic is that water and salt-added saline solution are heated in elevated temperatures by microwaves, while the ice is frozen in complete ice structures and cannot be heated. The third topic is that a carbon-gold compound is driven by relativistic electromagnetic radiations and is accelerated as a nanotube accelerator.

In order to study the propagation laws of acoustic wave of coal samples from the Upper Permian Xuanwei Formation in the east of Yunnan Province, China, under saturated water and dry conditions, the basic physical parameters, acoustic parameters and anisotropic parameters were obtained through the experiments. Based on FFT and wavelet analysis theory, the spectral characteristics of coal samples under different conditions were studied. The results show that physical parameters of coal samples in different directions have different values, that is, the anisotropy of coal samples is obvious. When the coal samples are saturated with water, the acoustic velocities and the attenuation coefficient increase, whereas the dominant frequency decreases. The signal amplitude of the frequency domain significantly decreases, that is, the internal structure of coal samples is damaged. The P-wave velocity and S-wave velocity increase with the increase of the confining pressure, whereas the anisotropy parameters decrease with the increase of the confining pressure. Overall, this study provides the basis to understand basic acoustic information and anisotropy characteristics of coal samples.

Mutual interference between different radar waveforms used in automotive radar applications is studied. The existing interference analysis is extended to a generalised radar‐to‐radar interference equation that covers most of the common interference scenarios for automotive radar systems. The outcome of the generalised equation is demonstrated for a number of typical scenarios where radars with different continuously transmitting waveforms are involved. The proposed equation can be used to characterise the received interference and its features by analysing the instantaneous beat frequency of the victim radar. Moreover, an interference analysis of phase‐coded frequency‐modulated continuous waveforms is performed and demonstrated experimentally by using real‐time automotive radars for the first time in the literature. The experimental results corroborate the interference analysis of different waveforms and validate the proposed generalised interference equation under various conditions.

Conventional wisdom suggests that the combination of semi-Lagrangian advection and an implicit treatment of gravity wave terms should result in a combined scheme for the shallow-water equations stable for high Courant numbers. This wisdom is well justified by linear analysis of the system about a uniform reference state with constant fluid depth and velocity, but it is only assumed to hold true in more complex scenarios. This work finds that this conventional wisdom no longer holds in more complicated flow regimes, in particular when the background state is given by steady-state flow past topography. Instead, this background state admits a wide range of instabilities that can lead to noise in atmospheric forecasts. Significance Statement This work shows that solutions to the shallow-water equations with a semi-Lagrangian treatment of advection and an implicit, time-centered treatment of gravity wave terms can be unstable when there is a background state of flow over topography. This basic algorithm is used by many operational weather-forecasting models to simulate the meteorological equations, and showing an instability in the simplified, shallow-water system suggests that a similar mechanism may be responsible for “noise” in operational weather forecasts under some circumstances. If this problem can be addressed, it could allow numerical weather models to operate with less dissipation, improving forecast quality.

Dual-winding bearingless flux-switching permanent magnet motor (BFSPMM) is composed of power winding and suspension winding. The permanent magnet and the power winding provide a biased air gap magnetic field, and the suspension winding generates an air gap modulation magnetic field. The structure of stator and rotor are double salient poles. This paper proposes a subdomain model for on-load field prediction in the Dual-winding BFSPMM. In the developed model, the field domain is divided into seven types of subdomains, viz.rotor slot, internal air gap, stator slot, permanent magnet slot upper layer, permanent magnet slot lower layer, permanent magnet, and external air gap. The electromagnetic parameters of the motor are analyzed, including air gap flux density, flux linkage, back-EMF, suspension force, and electromagnetic torque. Based on the principle of conservation of magnetomotive force, a distributed equivalent magnetic circuit model is proposed to compensate for the magnetic saturation. Finally, the analytical predictions are verified by finite-element analysis and prototype experiments.

We present a methodology to simulate the impact of the atmospheric models in the background particle flux on ground detectors using the Global Data Assimilation System. The methodology was within the ARTI simulation framework developed by the Latin American Giant Observatory Collaboration. The ground-level secondary flux simulations were performed in a tropical climate in the city of Bucaramanga, Colombia. To validate our methodology, we built monthly profiles over Malargüe between 2006 and 2011, comparing the maximum atmospheric depth, Xmax, with those calculated with the Auger atmospheric option in CORSIKA. The results show significant differences between the predefined CORSIKA atmospheres and their corresponding Global Data Assimilation System atmospheric profiles.

In this paper, the direct current (DC) winding induced voltage in wound-field flux-switching (WFFS) machines is qualitatively analyzed with air-gap field modulation principle. Operation principle and effective harmonics of DC winding induced voltage are modelled and deduced. It is found that only air-gap field harmonics with specific spatial orders, which numerically equals to odd times of half stator poles, can contribute to DC winding induced voltage. Harmonic order of DC winding induced voltages under open-circuit only, armature reaction only, and on-load condition, are predicted for m-phase WFFS machines with any feasible stator/rotor pole number combinations. Different armature winding configurations, including concentrated winding and distributed winding, are also analyzed and compared using the winding factor. Finite element analysis is employed to verify the prediction results. Finally, a prototype is built and tested for validation.

The forecasting of time series provides great convenience in our daily life. Studies of time series forecasting have been used in many fields such as financial models, weather, and traffic patterns. In this paper, we propose a model fusion-based time series forecasting to improve the forecasting accuracy and efficiency. We propose a time series forecasting scheme based on a multivariate grey model and uses artificial fish swarm algorithm to optimize the settings. We then propose two fusion models with the grey model-based schemes on two different perspectives: data decomposition, and weighted summation. We conduct evaluations based on real data series and compared them with other forecasting models. Results show that our model can achieve good prediction accuracy and efficiency, which can be used for time series forecasting in different scenarios.

An isentropic 1½-layer model based on modified shallow-water equations is presented, including terms mimicking convection and precipitation. This model is an updated version of the isopycnal single-layer modified rotating shallow water (modRSW) model. The clearer link between fluid temperature and model variables together with a double-layer structure make this revised, isentropic model a more suitable tool to achieve our future goal: to conduct idealized experiments for investigating satellite data assimilation. The numerical model implementation is verified against an analytical solution for stationary waves in a rotating fluid, based on Shrira’s methodology for the isopycnal case. Recovery of the equivalent isopycnal model is also verified, both analytically and numerically. With convection and precipitation added, we show how complex model dynamics can be achieved exploiting rotation and relaxation to a meridional jet in a periodic domain. This solution represents a useful reference simulation or “truth” in conducting future (satellite) data assimilation experiments, with additional atmospheric conditions and data. A formal analytical derivation of the isentropic 1½-layer model from an isentropic two-layer model without convection and precipitation is shown in a companion paper (Part II).

In view of the classical Lucas-Washburn equation, which can only describe the spontaneous imbibition of single wetted capillary, a tilted composite capillary model with circular cross section, composed of different wettability capillary wall was established. The model can describe the spontaneous oil-water imbibition of water-wet capillary, oil-wet capillary and mixed wetting capillary. Through numerical solution of the model equation, it is found that the component content of the capillary walls, the capillary radius and the oil-water viscosity ratio have great effects on the spontaneous oil-water imbibition. Effects of capillary inclination angle and inertia force on spontaneous oil-water imbibition are related to the capillary scale. Effects of capillary inclination angle and inertia force can be ignored in small radius capillary, while effects of inclination angle and inertia force can not be ignored in large radius capillary.

Optical communication has been employed in a wide range of applications, including the terrestrial, submarine, inter-satellite, and even space communication. It is particularly successful in fiber-based communication networks that vastly reshape modern life through the Internet. With the intensified activities such as undersea resource exploration, ecosystem monitoring, and recreation, underwater is an exciting new arena for optical wireless communication (OWC). In this paper, we review the recent progress of underwater and water-air OWC systems. Channel characterization, communication system design, and performance investigations are given. Critical limitations and effective mitigation methods to overcome the influence of bubbles and waves are presented. We also address the current issues for proper performance comparison under different wave conditions. With further research in channel modeling, device innovation, and system design optimization, practical and robust underwater and water-air OWC systems can be realized.

The clouds in the Atlantic trade-wind region are known to have an important role in the global climate system. Acquiring a comprehensive characterization of these clouds based on observations is a challenge, but it is a necessary piece of information for the evaluation of their representation in models. An exploration of how the macrophysical and microphysical cloud properties and organization of the cloud field impact the large-scale cloud radiative forcing is presented here. Direct measurements of the cloud radiative effects from the Broadband AirCrAft RaDiometer Instrumentation (BACARDI) on board the High Altitude and LOng Range Research Aircraft (HALO) and cloud observations from the GOES-16 satellite during the Elucidating the role of clouds-circulation coupling in climate (EUREC4A) campaign provide evidence to demonstrate what drives the cloud radiative effects in shallow trade-wind clouds. We find that the solar and terrestrial radiative effects of these clouds are largely driven by their macrophysical properties (cloud fraction and a scene-averaged liquid water path). However, we also conclude that the microphysical properties, cloud top height and the organization of the cloud field demonstrate an increasing relevance in determining the cloud radiative effects as the cloud fraction increases.

Underwater navigation system is an indispensable part for autonomous underwater vehicles. Due to the indiscernibility of satellite signal, however, the underwater navigation problem is quite challenging, and a satellite-free navigation scheme should be looked for. Polarization navigation, inspired by insects’ capability of autonomous homing and foraging, is an alternative solution to satellite navigation with great application potential. Underwater polarization provides an indirect sun compass to animals for orientation determination. However, it is difficult to apply terrestrial solar-tracking methodologies in underwater situations due to the refraction of polarized skylight at the air–water interface. To resolve this issue, an underwater solar-tracking algorithm is developed based on the underwater refraction-polarization pattern inside the Snell's window. By employing Snell's law and Fresnel refraction formula to decouple the refractive ray bending and polarization deflection, the celestial polarization pattern is obtained based on underwater measurement. To further improve the accuracy, the degree of polarization is employed as a weight factor for E-vector. A long-lasting underwater experiment was conducted to validate the effectiveness of the proposed approach, and the results showed the root-mean-square errors of solar zenith and azimuth employing this algorithm were 0.3° and 1.3°, respectively. Our experimental results show that the refraction-polarization pattern inside the Snell's window exhibits immense potential to improve the solar-tracking accuracy for underwater navigation.

Based on the extended Huygens–Fresnel principle and Wigner distribution function (WDF), the influence of anisotropic ocean turbulence on effective radius of curvature (ERC) for partially coherent Hermite–Gaussian (PCHG) beams is studied in detail. Our numerical results show that the beam orders and the anisotropic ocean turbulence factors have a certain influence on ERC of PCHG beams propagating in anisotropic ocean turbulence. Besides, ocean turbulence parameters and beam initial parameters would exert different influence on ERC of PCHG beams propagating in anisotropic ocean turbulence. In addition, Rayleigh range of PCHG beams propagating in anisotropic ocean turbulence decreases with increasing anisotropic ocean turbulence factors. These findings may be used for anisotropic ocean optical communications of PCHG beams.