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Tropical counting tools are useful for many enumerative questions. We count tropical multinodal surfaces using floor plans, looking at the case when two nodes are tropically close together, i.e., unseparated. We generalize tropical floor plans to recover the count of multinodal curves. We then prove that for $\delta=2$ or $3$ nodes, tropical surfaces with unseparated nodes contribute asymptotically to the second order term of the polynomial giving the degree of the family of complex projective surfaces in $\mathbb{P}^3$ of degree $d$ with $\delta$ nodes. We classify when two nodes in a surface tropicalize to a vertex dual to a polytope with 6 lattice points, and prove that this only happens for projective degree $d$ surfaces satisfying point conditions in Mikhalkin position when $d>4$., Comment: 15 figures, 37 pages + appendix and references

Long-span bridges in mountainous areas are greatly disturbed by wind, and the wind field in the mountain gorge bridge site is extremely complex. Therefore, it is of great engineering significance to accurately evaluate the wind field characteristics of this kind of terrain. In this paper, to enhance understanding of this kind of wind field, the wind field in a mountainous gorge is measured for a long time using wind radar, and the mean wind parameters is statistically analyzed. The results show that the mean wind parameters vary greatly under different wind directions, and the wind speed profile does not meet the power-law model. Therefore, a mixed model suitable for the wind speed profile in a mountainous gorge is proposed. Additionally, GEV distribution and Logistic distribution are found to be suitable for describing the distribution characteristics of wind speed and angle of attack, respectively. In addition, considering the correlation between wind parameters, this paper also constructs the joint probability model of wind speed and angle of attack at different heights by the Copula function. Thus, a combined wind parameters profile model is developed under different exceedance probabilities based on the inverse first-order reliability method (IFORM). This study can provide a reference for the construction of the joint probability model of wind parameters.

By using multiple sets of assimilation and reanalysis data, the spatial distribution and temporal evolution of the precipitation over the Tibetan Plateau (TP) in boreal summer are investigated. The results show that, the climatological precipitation tends to increase towards the southeast, while it increases in the morning, reaches a peak around 21 Beijing Time Coordinate (BTC), and tends to decay after midnight in the diurnal time scale. To understand the roles of atmospheric dynamic and thermodynamic processes in causing the diurnal variation of summer precipitation over the southeastern TP, the atmospheric precipitation and moisture budget are conducted. The budget result shows that, there is a good corresponding relationship between the precipitation and moisture tendency in the night, and the anomalous vertical motion has a key effect on the diurnal variation of the precipitation. In the developing phase of the anomalous ascending motion (17-20 BTC), the anomalous linear vorticity (temperature) advections over the southeastern TP contribute to the anomalous ascending motion, and the major contribution arises from the anomalous vorticity (temperature) field over the western TP. Due to the negative zonal vorticity (temperature) gradient, the mean westerly winds induce positive advection that support the ascending motion.

Wind profiler radars are capable of measuring three-dimensional wind profiles at various altitudes of the atmosphere, at very high temporal and spatial resolution. The Advanced Centre for Atmospheric Radar Research (ACARR), located at Cochin University of Science and Technology (CUSAT), operates the World’s first 205 MHz stratospheretroposphere wind profiler radar which provides three-dimensional wind profiles for an altitude range of 315 m to 20 km. During non-rainy condition, the radar Doppler power spectrum bears the signature of ambient air motion whereas during rainy conditions, it contains signatures of both ambient air motion and fall velocity of rain droplets. The classification of Doppler power spectra for rainy (Precipitation) and non-rainy (Clear) conditions is necessary as wind profile retrieval from the former needs careful separation of ambient air motion from fall velocity of droplets. A manual classification of the power spectrum is cumbersome, time-consuming, and therefore not practical due to the vast database. This work intends to automate Doppler power spectra classification using the deep learning Convolutional Neural Network (CNN). The proposed Convolutional Neural Network model gives a k-fold validation accuracy of 99.77 % and testing accuracy of 99.60% for power spectra classification. The performance of CNN is compared against other popular machine learning classifiers such as Support Vector Machine, Decision Tree, K Nearest Neighbour and Naive Bayes. The performance comparison results show that the proposed CNN outperforms other models in radar Doppler power spectra classification.

In their Letter, Tsiaras et al. reported the detection of water vapour in the atmosphere of K2-18 b, an exoplanet of 7 to 10 Earth masses located in the habitable zone of an M-dwarf star. The detection is based on an absorption feature seen at 1.4 $\mu$m in observations of the transiting exoplanet with the Hubble Space Telescope/Wide Field Camera 3. We have simulated the mean temperature structure and composition of K2-18b using a radiative-convective equilibrium model and we present here the corresponding transit spectroscopy calculations. We argue that the reported absorption is most likely due to methane, a gas expected to be abundant in the hydrogen-helium atmosphere of cold sub-Neptunes. More generally, we show that the 1.4-$\mu$m absorption seen in transit spectra is not diagnostic of the presence of water vapour for sub-Neptunes having an effective temperature less than 600 K and that water vapour dominates over methane at this wavelength only at larger temperatures., Comment: This preprint has not undergone any post-submission improvements or corrections. The Version of Record of this article is published in Nature Astronomy (Matters Arising), and is available online at https://www.nature.com/articles/s41550-022-01678-z

Starting from the general, governing equations for a viscous, compressible fluid, with an associated description of its thermodynamics, we outline an asymptotic derivation based on the thin-shell approximation. [The details appear in another publication.] This produces a reduced system of equations which retain all the dynamics and thermodynamics of the steady atmosphere, the thin-shell approximation alone being the basis for the construction of the asymptotic solution. The leading order describes the background state of the atmosphere, and the next order provides a simple set of equations that can be used to investigate, for example, the Walker circulation, a particular atmospheric flow which is restricted to the neighbourhood of the Equator across the Pacific Ocean. Our formulation of this problem shows, explicitly and in detail, how the pressure and temperature gradients in the azimuthal direction drive the circulation; this extends the usual physical arguments used to describe the Walker circulation. An initial investigation highlights the rȏle of the variable eddy viscosity and then, on the basis of these observations, a solution is obtained which describes in detail the velocity and temperature fields in the Walker cell. In particular, we present an example of the temperature profile and of the streamlines for the flow along the Equator and which is bounded above by the tropopause. Further details of the Walker circulation are given, together with an identification of the heat sources that drive the motion. Finally, we comment on the changes to the flow pattern that arise during an El Niño event.

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.

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.

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.

Very low Earth orbits (VLEOs) have been proposed as a beneficial space mission regime due to their propensity to increase instrument spatial resolution and reduce launch cost per unit mass. However, for visual instruments, these benefits come at the cost of a decreased instrument swath width. This reduction results in longer revisit periods for regions on Earth and longer time until global coverage is achieved. Conversely, light detection and ranging (lidar) as an active remote sensing technique, can benefit from larger swath widths at lower altitudes, due to the increased signal-to-noise ratio. Investigation of this relationship shows that lidar swath width is inversely proportional to altitude squared, and, as a result, the number of spacecraft required to provide a desired lidar coverage also decreases approximately in inverse proportion to altitude squared. Investigation of suitable propulsion systems shows that although propellant mass and number of thrusters required for orbit maintenance increases with decreasing altitude, the overall system mass, and hence launch cost, will, in general, tend to decrease with decreasing altitude due to the lower number of spacecraft required. For a given mission, spacecraft bus, and propulsion system, a VLEO altitude can be identified that will result in the minimum overall mission cost.

This work presents a study of the applicability of laser-induced breakdown spectroscopy based on infrared transversally excited atmospheric CO2 pulsed laser for quantitative analysis of main inorganic elements in lignite coals. Calibration standards were prepared by mixing and pelleting an appropriate amount of rock reference material and graphite. Time-integrated spatially resolved measurements of analyte spectra of standard samples were used to construct univariate calibration curves of Al, Si, Ca, Fe and Mg. The spectral intensities of analytical lines were normalized by the carbon spectral line to compensate for the shot-to-shot fluctuation of plasma parameters. The obtained curves of growth have good linearity in a wide range of concentrations (up to 1% for Al and 3% for Si). Correlation coefficients were in the range of 0.955–0.993, depending on the element. Measured limits of detection (from 2.4 to 25 ppm for analyzed metals and 61 ppm for Si) are low enough to control the coal combustion process in power plants. The Stark-broadening and the Boltzmann plot method were used to determine apparent values of excitation temperatures and electron number densities. A relatively small but measurable influence of the concentration of metal elements on the plasma parameters was observed, which should be considered in quantitative analysis of coal samples with higher inorganic elements content.

The aim of this work is the evaluation of the influence of the rotation on the turbulence and on the entrainment within a buoyant plume. A series of laboratory experiments are performed in the rotating water tank of the Turlab in Torino (Italy) producing negatively buoyant plumes emitted from a finite circular source, with varying plume density and background rotations. Thanks to the particle image velocimetry technique, we obtain a detailed description of the velocity field within the plume. We present the results in term of mean velocity, turbulence and vorticity fields. The swirling strength analysis is also performed to identify the coherent structures. Finally, the velocity spectra are examined. We find that the rotation affects the dynamics of the plume increasing the turbulence and, in particular, the number of structures developed along the plume edges, which feeds the entrainment. The analysis of the mean velocity fields also allows us to quantify the turbulent entrainemnt of ambient fluid within the buoyant plume, and discuss the role of rotation in this process.

Jupiter’s atmosphere is one of the most turbulent places in the solar system. Whereas observations of lightning and thunderstorms point to moist convection as a small-scale energy source for Jupiter’s large-scale vortices and zonal jets, this has never been demonstrated due to the coarse resolution of pre-Juno measurements. The Juno spacecraft discovered that Jovian high latitudes host a cluster of large cyclones with diameter of around 5,000 km, each associated with intermediate- (roughly between 500 and 1,600 km) and smaller-scale vortices and filaments of around 100 km. Here, we analyse infrared images from Juno with a high resolution of 10 km. We unveil a dynamical regime associated with a significant energy source of convective origin that peaks at 100 km scales and in which energy gets subsequently transferred upscale to the large circumpolar and polar cyclones. Although this energy route has never been observed on another planet, it is surprisingly consistent with idealized studies of rapidly rotating Rayleigh–Bénard convection, lending theoretical support to our analyses. This energy route is expected to enhance the heat transfer from Jupiter’s hot interior to its troposphere and may also be relevant to the Earth’s atmosphere, helping us better understand the dynamics of our own planet.

Tropical ideals are a class of ideals in the tropical polynomial semiring that combinatorially abstracts the possible collections of supports of all polynomials in an ideal over a field. We study zero-dimensional tropical ideals I with Boolean coefficients in which all underlying matroids are paving matroids, or equivalently, in which all polynomials of minimal support have support of size deg(I) or deg(I)+1 -- we call them paving tropical ideals. We show that paving tropical ideals of degree d+1 are in bijection with $\mathbb Z^n$-invariant d-partitions of $\mathbb Z^n$. This implies that zero-dimensional tropical ideals of degree 3 with Boolean coefficients are in bijection with $\mathbb Z^n$-invariant 2-partitions of quotient groups of the form $\mathbb Z^n/L$. We provide several applications of these techniques, including a construction of uncountably many zero-dimensional degree-3 tropical ideals in one variable with Boolean coefficients, and new examples of non-realizable zero-dimensional tropical ideals., Comment: 13 pages

In this paper, a scheme of dual-Doppler radar wind analysis based on a three-dimensional variational method is proposed and performed in two steps. First, the horizontal wind field is simultaneously recovered through minimizing a cost function defined as a radial observation term with the standard conjugate gradient method, avoiding a weighting parameter specification step. Compared with conventional dual-Doppler wind synthesis approaches, this variational method minimizes errors caused by interpolation from radar observation to analysis grid in the iterative solution process, which is one of the main sources of errors. Then, through the accelerated Liebmann method, the vertical velocity is further re-estimated as an extra step by solving the Poisson equation with impermeable conditions imposed at the ground and near the tropopause. The Poisson equation defined by the second derivative of the vertical velocity is derived from the mass continuity equation. Compared with the method proposed by O'Brien, this method is less sensitive to the uncertainty of the boundary conditions and has better stability and reliability. Furthermore, the method proposed in this paper is applied to Doppler radar observation of a squall line process. It is shown that the retrieved vertical wind profile agrees well with the vertical profile obtained with the velocity–azimuth display (VAD) method, and the retrieved radial velocity as well as the analyzed positive and negative velocity centers and horizontal wind shear of the squall line are in accord with radar observations. There is a good correspondence between the divergence field of the derived wind field and the vertical velocity. And, the horizontal and vertical circulations within and around the squall line, as well as strong updrafts, the associated downdrafts, and associated rear inflow of the bow echo, are analyzed well. It is worth mentioning that the variational method in this paper can be applied to simultaneously synthesize the three-dimensional wind field from multiple-Doppler radar observations.

A conventional method to define short-term climate anomalies for atmospheric and oceanic variables, recommended by the World Meteorological Organization (WMO), is the departure from a 30-yr climatological mean in the preceding three decades. Such a method, however, introduces spurious errors such as sudden jumps and artificial trends. A new method, named a trend correctional method, is introduced to eliminate the errors. To demonstrate the capability of this new method, we examine a set of idealized cases first by superposing a “true” interannual or interdecadal signal onto a linear or a nonlinear trend. Comparing to the conventional method, the trend correctional method is able to retain, to a large extent, the “true” anomaly signals. Next, we examined real-time indices. The anomaly time series derived based on the trend correctional method show a better agreement with the observed anomaly series. The root-mean-square error is greatly improved, comparing to that calculated based on the conventional method. Therefore, the results from both the idealized and real cases demonstrate that the new method has a clear advantage to the conventional method in deriving true climate anomalies, in particular under the ongoing global warming circumstance.

In response to the growing demand for the global energy supply chain, wind power has become an important research subject among studies in the advancement of renewable energy sources. The major concern is the stochastic volatility of weather conditions that hinder the development of wind power forecasting approaches. To address this issue, the current study proposes a weather prediction method divided into two models for wind speed and atmospheric system forecasting. First, the data-based model incorporated with wavelet transform and recurrent neural networks is employed to predict the wind speed. Second, the physics-informed echo state network was used to learn the chaotic behavior of the atmospheric system. The findings were validated with a case study conducted on wind speed data from Turkmenistan. The results suggest the outperformance of physics-informed model for accurate and reliable forecasting analysis, which indicates the potential for implementation in wind energy analysis.

The entrainment coefficient of the pure plume, the ratio of the radial velocity of the entraining fluid at the edge of the plume to the axial velocity, is characterized by a remarkable deviation from the actual value in references. To a turbulent flow with Gaussian profiles, the entrainment coefficient is accepted in a considerably wide range from 0.07 to 0.11 for pure plumes. In this study, the entrainment coefficient of a pure plume is determined by analyzing the stratified interface formed between fresh water and a buoyant fluid in a confined space. The interface position is determined using digital image processing while conducting salt-water experiments. The displacement of the virtual origin of the real plume is added to the original heights of the confined space and stratified interface because the plume in the laboratory is from a source of finite area rather than from a point. The two virtual source position determination methods are compared; the one where the ratio of the displacement of the virtual origin to the nozzle diameter is related only to the source parameter Γ is selected for the theoretical analysis. The experimental data of the source parameter Γ and corresponding entrainment coefficients indicate that the α value of the pure plume is 0.09251 when using the interpolation method. This value is validated through displacement experiments on a pure plume created by supplying salt water through the nozzle in a laboratory. Further, the entrainment coefficient of a turbulent jet is determined based on the stratified interface behavior in a confined space; the experimental results support the speculation that the entrainment coefficient of the pure jet should be 0.057. The experimental data of the entrainment coefficient α plotted against parameter Γ in the available literature are compared with those estimated from semi-empirical equations with two asymptotic values suggested in this paper.

As an important parameter of the Earth’s energy budget, the planetary albedo of Earth varies with the dynamics of atmospheric and surface variables. In this study, we investigated the spatiotemporal characteristics and driving factors of the global planetary albedo using the Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) dataset and the Geodetector method. The results revealed that the planetary albedo can be decomposed into atmospheric and surface contributions, and the planetary albedo in the middle and low latitudes was predominantly affected by the atmospheric contribution. The global planetary albedo and the atmospheric and surface contributions exhibited decreasing trends of − 0.0020, − 0.0015, and − 0.0004/decade from 2001 to 2018, respectively, which were closely related to the variations of atmospheric and surface variables. The cloud fraction was the driving factor of the atmospheric contribution in the middle and low latitudes, and its influence was further enhanced by the aerosol optical thickness (AOT), ice water path (IWP), and liquid water path (LWP). The snow/ice coverage and normalized difference vegetation index (NDVI) were the driving factors of the surface contribution in the snow/ice-covered and vegetated areas, respectively. The interaction relationships between the surface variables were mainly bi-enhanced and nonlinearly enhanced. These results provide useful information about the driving factors of the planetary albedo and are benefit for improving the parametrization of the planetary albedo.

Facing the major scientific issues of the global carbon cycle and the monitoring demand for carbon emission reduction all over the world, this paper researches and develops a new calculation method for space-based remote sensing detection of greenhouse gas-flux based on the atmospheric boundary layer turbulence transport theory and the active detection of coherent differential absorption lidar system. By obtaining the atmospheric wind profile information, gas concentration profile information and the new calculation method for space-based gas-flux proposed in this paper, the near-surface gas-flux information in the detected area can be directly obtained. So it can innovatively realize the space-based active and direct remote sensing of the atmospheric boundary layer gas-flux. The method in this paper not only can make up the blank in the space-based active detection of greenhouse gas-flux, but also can realize the high spatial and temporal resolution measurement of the three-dimensional atmospheric motion. It reduces assumptions and errors of the existing model based on the column concentration assimilation inversion method, so it can realize a direct and active observation of global multi-scale, high-quality, long-sequence gas-flux.

We show the existence of nontrivial stationary weak solutions to the surface quasi-geostrophic equations on the two dimensional periodic torus., 8 pages, improved regularity and added references

Due to the high height of the refinery flares, the wind velocity plays an important role in flame shape and the resulting temperature distribution in flare body. The investigation of wind velocity effect on flame pulldown (downwash) can provide effective solution to avoid the flame pulldown problem and burning the flare tip. In this study, using the three-dimensional numerical simulation of the combustion, the performance of the Khangiran gas refinery flares is evaluated as a case study. For this reason, the effect of wind velocity is studied on influential parameters such as combustion efficiency, temperature distribution, pollutant emissions and pulldown phenomenon. Results show that the wind velocity has significant effect on temperature distribution, air–fuel mixing and combustion efficiency since with increasing the wind velocity to more than 4 m/s, the flame axis is diverted from vertical direction and is oriented horizontally based on the wind velocity. In addition, by increasing the wind velocity from 4 m/s to its maximum value at Khangiran region (11 m/s), the combustion efficiency decreases by 5%.

In recent decades, warming temperatures have caused sharp reductions in the volume of sea ice in the Arctic Ocean. Predicting changes in Arctic sea ice thickness is vital in a changing Arctic for making decisions about shipping and resource management in the region. We propose a statistical spatio-temporal two-stage model for sea ice thickness and use it to generate probabilistic forecasts up to three months into the future. Our approach combines a contour model to predict the ice-covered region with a Gaussian random field to model ice thickness conditional on the ice-covered region. Using the most complete estimates of sea ice thickness currently available, we apply our method to forecast Arctic sea ice thickness. Point predictions and prediction intervals from our model offer comparable accuracy and improved calibration compared with existing forecasts. We show that existing forecasts produced by ensembles of deterministic dynamic models can have large errors and poor calibration. We also show that our statistical model can generate good forecasts of aggregate quantities such as overall and regional sea ice volume. Supplementary materials accompanying this paper appear on-line.

In this paper, an ice floe inner stress caused by the wave-induced bending moment is derived to estimate the stress failure of ice floe. The strain and stress failures are combined to establish a wave-induced ice yield scheme. We added ice stress and strain failure module in the Finite-Volume Community Ocean Model (FVCOM), which already includes module of ice-induced wave attenuation. Thus a fully coupled wave-ice dynamical interaction model is established based on the ice and wave modules of FVCOM. This model is applied to reproduce the ice and wave fields of the breakup events observed during the second Sea Ice Physics and Ecosystem Experiment (SIPEX-2) voyage. The simulation results show that by adopting the combined wave-induced ice yield scheme, the model can successfully predict the ice breakup events, which the strain failure model is unable to predict. By comparing the critical significant wave height deduced from strain and stress failure schemes, it is concluded that the ice breakup is caused by the strain failure when wave periods are shorter than a threshold value, while the stress failure is the main reason for the ice breakup when wave periods are longer than the threshold value. Neglecting either of these two ice-break inducement mechanisms could overestimate the ice floe size, and thus underestimate the velocity of the ice lateral melt and increase the error of simulation of polar ice extent.

Roughness-induced emission from ocean surfaces is one of the main issues that affects the retrieval accuracy of sea surface salinity remote sensing. In previous studies, the correction of roughness effect mainly depended on wind speeds retrieved from scatterometers or those provided by other means, which necessitates a high requirement for accuracy and synchronicity of wind-speed measurements. The aim of this study is to develop a novel roughness correction model of ocean emissivity for the salinity retrieval application. The combined active/passive observations of normalized radar cross-sections (NRCSs) and emissivities from ocean surfaces given by the L-band Aquarius/SAC-D mission, and the auxiliary wind directions collocated from the National Centers for Environmental Prediction (NCEP) dataset are used for model development. The model is validated against the observations and the Aquarius standard algorithms of roughness-induced emissivity correction. Comparisons between model computations and measurements indicate that the model has better accuracy in computing wind-induced brightness temperature in the upwind/downwind directions or for the surfaces with smaller NRCSs, which can be better than 0.3 K. However, for crosswind directions and larger NRCSs, the model accuracy is relatively low. A model using HH-polarized NRCSs yields better accuracy than that using VV-polarized ones. For a fair comparison to the Aquarius standard algorithms using wind speeds retrieved from multi-source data, the maximum likelihood estimation is employed to produce results combining our model calculations and those using other sources. Numerical simulations show that combined results basically have higher accuracy than the standard algorithms.

Efficient energy is crucial in reducing CO2 emissions. The researchers are digging for a new efficient source of energy in the modern era. Therefore, this study explores the dynamic impacts of energy efficiency and renewable energy consumption on CO2 emissions from 1991 to 2019 for China. By using the non-linear ARDL approach, we found that a negative shock in energy efficiency has a positive impact on CO2 emissions in long run. Furthermore, renewable energy consumption with positive shock has a negative significant impact on CO2 emissions, but negative shock in renewable energy consumption leads to increase pollution emissions in long run. Besides, positive shocks to energy efficiency and renewable energy consumption have also a favorable negative effect on CO2 emissions in the short run. While a negative shock in energy efficiency has only unobservable negative impacts on CO2 emissions in the short run. Based on findings, some policy measures are suggested to attain environmental sustainability in China.

We report an experimental study addressing the characteristic hydrodynamic transformations of unstable wave groups as well as JONSWAP wave fields propagating from deep-water towards shallow regions. Long zones of linearly rising floor levels have been installed to mimic a simplified coastal morphology. The breather surface elevation evolution data show a very good agreement with the depth-adapted nonlinear Schrodinger-type model. Our results suggest that the residual effects of four-wave resonance interactions in the shallower regions is relevant for the nonlinear group propagation over steep bottom topography slopes. When considering broadband JONSWAP processes, the model fails in predicting the evolution of kurtosis, independently of the values of significant wave height adopted. Nonetheless, consistency with the data is achieved when narrowing the spectrum of the JONSWAP wave field. Our study emphasizes the strong potential of weakly nonlinear frameworks in modeling complex wave shoaling problems and wave transformations in coastal zones.

Electromagnetic ion cyclotron (EMIC) emission is an efficient mechanism for scattering loss of energetic protons. Here, we report an event that provides both in-situ observation of energetic proton differential fluxes in the inner magnetosphere and precipitation of protons at ionospheric altitudes. During the 7–8 September 2015 geomagnetic storm the Van Allen Probes observed strong EMIC waves around L = 5 and a distinct decrement in fluxes of tens of keV protons around pitch angles 0°–45°. Meanwhile, precipitating protons at ionospheric altitudes were found to significantly enhanced (by several orders of magnitude), measured by NOAA 18 and 19 when they magnetically linked to the Van Allen Probe-A. By solving the Fokker-Planck diffusion equation, we show that EMIC waves can efficiently produce loss of energetic protons within about 2 h in the pitch angle range of ∼ 0°–45°, comparable to the satellite observations.

The Lagrangian eddies in the western Pacific Ocean are identified and analysed based on Maps of Sea Level Anomaly (MSLA) data from 1998 to 2018. By calculating the Lagrangian eddy advected by the AVISO velocity field, we analyzed the variations in Lagrangian eddies and the average transport effects on different time scales. By introducing the Nino coefficient, the lag response of the Lagrangian eddy to El Nino is found. These data are helpful to further explore the role of mesoscale eddies in ocean energy transfer. Through normalized chlorophyll data, we observed chlorophyll aggregation and hole effects caused by Lagrangian eddies. These findings demonstrate the important role of Lagrangian eddies in material transport. The transportation volume of the Lagrangian eddy is calculated quantitatively, and several major transport routes have been identified, which helps us to more accurately and objectively estimate the transport capacity of Lagrangian eddies in the western Pacific Ocean.

Nutrient fluxes at the sediment–water interface are essential for water quality and aquatic ecosystems. In this study, a unified expression for the sediment nutrient flux under different controlling modes is proposed by analytically solving the first-order linear partial differential equations describing nutrient transport in the sediment layer and overlying water. In particular, the analytical expression for the sediment nutrient flux due to bedform migration is derived, and the effects of bedform parameters, water depth, and sediment size are explored. With increasing flow velocity, the controlling mode of the sediment nutrient flux changes from diffusion to sand wave motion and then bed erosion, resulting in a significant increase in the flux. The water depth and sediment size indirectly affect the sediment nutrient flux by changing the critical velocity and the dimension and migration velocity of the sand waves. The physical meaning of each term of the analytical solution can be distinguished, which is beneficial for exploring the flux exchange at the sediment–water interface in mobile beds.

A two-zone model of the atmospheric circulation over a hemisphere is considered. The latitude φ of the boundary between the zone of the Rossby circulation regime at mid and high latitudes and the zone of the Hadley circulation regime at low latitudes serves as a model variable. The principle of maximum of the (information) entropy of the eddy regime within the Rossby regime zone is used to determine a statistical (climatic) equilibrium value of φ. Based on the proposed model, the question of atmospheric blocking action over the hemisphere is addressed. An attempt has been made to represent a blocking phenomenon as a necessary attribute of the atmospheric circulation in statistical equilibrium. The model suggests that long-term climate change related either to the (significant) global warming or to the (significant) global cooling, both respective to the current climate state, and quantified in terms of changes in latitude φ, leads to an increase in the probability of blocking action.

In the phase diagram of water, superionic ices with highly mobile protons within the stable oxygen sublattice have been predicted at high pressures. However, the existence of superionic ices and the location of the melting line have been challenging to determine from both theory and experiments, yielding contradictory results depending on the employed techniques and the interpretation of the data. Here we report high-pressure and high-temperature synchrotron X-ray diffraction and optical spectroscopy measurements of water in a laser-heated diamond anvil cell and reveal first-order phase transitions to ices with body-centred and face-centred cubic oxygen lattices. Based on the distinct density, increased optical conductivity and the greatly decreased fusion enthalpies, we assign these observed structures to the theoretically predicted superionic ice phases. Our measurements determine the pressure–temperature stability fields of superionic ice phases and the melting line, suggesting the presence of face-centred cubic superionic ice in water-rich giant planets, such as Neptune and Uranus. The melting line determined here is at higher temperatures than previously determined in static compression experiments, but it is in agreement with theoretical calculations and data from shock-wave experiments. Measurements of the phase diagram of water reveal first-order phase transitions to face- and body-centred cubic superionic ice phases. The former is suggested to be present in the interior of ice giant planets.

This paper presents the framework for fractal relation of channel network with source basin area. To this end, a various pattern of channel networks is extracted corresponding to variable source basin area for the single river basin. The decrease of the source basin area causes the bifurcation process of the channel network, resulting in the expansion and elongation of the channel network. Scale invariance of channel network could be regarded as the result stemming from cooperation or competition between the elongation and expansion of channel network due to variable source basin area so that fractal properties of channel network would constitute a kind of balanced geomorphologic features of those two entities of the bifurcation process of the channel network. Scaling of channel network with variable source basin area could be a reasonable framework for fractal relation of channel network in terms of the link based classification scheme.

China’s Mars exploration mission has stimulated tremendous interest in planetary science exploration recently. To propose potential scientific research projects, this study presents a concept simulation for the measurement of Martian atmospheric winds using the Doppler Michelson interferometry technique. The simulation is based on the satellite instrument initially designed for the Dynamic Atmosphere Mars Observer (DYNAMO) project to measure vertical profiles of winds from the 1.27 μm airglow observations in the Martian atmosphere. A comprehensive DYNAMO measurement simulation forward model based on an orbit submodel, an atmospheric background field submodel, and an instrument submodel is developed using the Michelson equation. The simulated interferogram signal over the field of view (FOV) calculated by the forward model is associated with the filter transmittance function, column emission rate of airglow, wind velocity, temperature, and the Michelson phase. The agreement between the derived atmospheric signals from the simulated interferogram without altitude inversion and the input parameters used to initiate the forward model confirms the validity of the forward model.

We study tropically planar graphs, which are the graphs that appear in smooth tropical plane curves. We develop necessary conditions for graphs to be tropically planar, and compute the number of tropically planar graphs up to genus $7$. We provide non-trivial upper and lower bounds on the number of tropically planar graphs, and prove that asymptotically $0\%$ of connected trivalent planar graphs are tropically planar., Comment: 28 pages, 29 figures; updated to correct erroneous counts at the end of Section 3

In the effect of periodically varying wind speeds, a wind turbine in an external field environment often works under stall conditions. This paper explores the factors that average wind speed, wind speed amplitude, and oscillation frequency resulted in the changes in blade torque by dynamic stall. According to the blade surface flow field during the dynamic change of wind speed, the law of surface pressure change of the blade in the period of periodic stall is analyzed, and the power changes of the wind turbine blade in the stages of no stall, light stall, and deep stall are studied. As a result, as the oscillation frequency increases, the amount of torque change also increases, and the maximum torque also increases. When the average wind speed increases, the torque experienced by the blades decreases stepwise. As the wind speed amplitude increases, the area of the closed-loop curve where the torque varies with the wind speed continues to expand. Accurately understanding the impact of dynamic stalls and stall delays on wind turbines can further improve the efficiency of wind turbines.

The reduction of CO2 emissions is greatly needed in the context of global warming. Among all technologies for reducing CO2 concentrations, the capture of CO2 with ionic liquids is a good candidate, especially in industry. In this study, a mathematical expression for characterizing the temporal evolution of the CO2 absorption amount of an ionic liquid is derived using the probability method based on two entropy functions: Shannon entropy and general index entropy. Both the Shannon entropy and general index entropy lead to the same entropic expression, which can model the CO2 absorption process as the absorption time advances from null to infinity. Its accuracy is validated by comparison with ten experimental datasets with a high average correlation coefficient value of 0.983, a low relative bias value of 0.054 and a low relative root mean square error value of 0.134. Moreover, the proposed maximum CO2 absorption capacity in the entropic model is presented to be a function of some factors, including the type of ionic liquid, temperature, gas flow rate, and water content. This derived entropic model has a simple mathematical form, showing its potential to predict the temporal variation in the CO2 absorption amount under some conditions of interest as long as the type of ionic liquid, temperature, gas inflow rate and water content are provided from limited datasets.

Given a graph G, the burning number of G is the smallest integer k for which there are vertices $$x_1, x_2,\ldots ,x_k$$ such that $$(x_1,x_2,\ldots ,x_k)$$ is a burning sequence of G. It has been shown that the graph burning problem is NP-complete, even for trees with maximum degree three, or linear forests. A t-unicyclic graph is a unicycle graph in which the unique vertex in the graph with degree greater than two has degree $$ t + 2 $$ . In this paper, we first present the bounds for the burning number of t-unicyclic graphs, and then use the burning numbers of linear forests with at most three components to determine the burning number of all t-unicyclic graphs for $$t\le 2$$ .

We propose a new model for the pricing of wind power futures written on the wind power production index. Our approach is based on an arithmetic multi-factor pure-jump Ornstein–Uhlenbeck setup with time-dependent coefficients. We express the wind power production index and the corresponding futures price in terms of Fourier integrals and derive the related time dynamics. We conclude the paper by an investigation of the risk premium associated with our wind power model.

The characteristics of the waves around a lagoon entrance in South China Sea were observed during the past one and half years based on the wave measurements. The measured results show that the monsoon plays an important role. In summer, waves mostly come from the southeast, among which the wave components of non-dimensional periods larger than 0.2 are fetch-trapped waves. In winter the waves may be divided into two groups, the fetch-trapped waves and the waves from the open sea. The skewness of the directional distribution functions is within ±8 around zero. The power relationship between the direction spread and kurtosis is also investigated. Besides, it is found that the waves with the significant wave heights greater than 1.5 m are caused by typhoons or cold air. The frequency components of wave energy driven by cold air appear in the high frequency range at first, and change to the lower frequency range afterwards. The waves driven by typhoon mostly come from the open sea.

Earth System Science refers to the integrated study of physical, biological, chemical, and social processes that define the conditions on Earth. The earth system approach looks at the planet, linking the atmosphere, oceans and hydrosphere, the terrestrial realm, cryosphere and the biosphere. Earth system science services include weather and climate forecasts, ocean and coastal state forecasts, warnings, seismological monitoring, exploration of polar regions, and living and non-living resources of the oceans.

Complex network theory provides an important tool for the analysis of complex systems such as the Earth’s climate. In this context, functional climate networks can be constructed using a spatiotemporal climate dataset and a suitable time series distance function. The resulting coarse-grained view on climate variability consists of representing distinct areas on the globe (i.e., grid cells) by nodes and connecting pairs of nodes that present similar time series. One fundamental concern when constructing such a functional climate network is the definition of a metric that captures the mutual similarity between time series. Here we study systematically the effect of 29 time series distance functions on functional climate network construction based on global temperature data. We observe that the distance functions previously used in the literature commonly generate very similar networks while alternative ones result in rather distinct network structures and reveal different long-distance connection patterns. These patterns are highly important for the study of climate dynamics since they generally represent pathways for the long-distance transportation of energy and can be used to forecast climate variability on subseasonal to interannual or even decadal scales. Therefore, we propose the measures studied here as alternatives for the analysis of climate variability and to further exploit their complementary capability of capturing different aspects of the underlying dynamics that may help gaining a more holistic empirical understanding of the global climate system.

In this study, we diagnose the time variability and vertical structure of the high- and low-frequency motions on the Mississippi-Alabama Shelf as observed with a bottom-mounted ADCP (Acoustic Doppler Current Profiler) and CTD (Conductivity-Temperature-Depth). The mooring was deployed about 20 km offshore of Mobile Bay for a period from May 17 to August 23, 2018. At this latitude, the diurnal land and sea breeze has the same frequency as the local inertial frequency. Similar to the wind, the observed high-frequency baroclinic velocities (> 30 cm/s) have a broadband diurnal peak and more energy in the clockwise motions. About 60% of the variance in these motions is due to mode 1, which resembles a two-layer structure with surface and bottom velocities that are 180∘ out of phase. These are all characteristics of wind-driven motions that interact with the coastal wall. The month of June features the best conditions for energetic near-inertial motions: upwelling, consistent sea breeze, and a more continuous instead of a two-layer stratification. This causes near-inertial energy to be also projected on a baroclinic mode 2, featuring a subsurface maximum. This maximum may be attributed to the downward propagation of near-inertial internal wave energy. The observed alongshore low-frequency flows and the up- and downwelling are mostly driven by low-frequency winds. About 83% of the variance in the alongshore low-frequency flows is due to mode 1, which eigenfunction resembles a vertically sheared flow. We find that the amplitude of the near-inertial motions is modulated by the up- and downwelling. During downwelling, the near-inertial baroclinic kinetic energy is greatly reduced because of a reduction in stratification and weaker diurnal winds.

The high-energy laser (HEL) has recently been in the spotlight for the most challenging military applications because it allows the warfighter to be capable of directly damaging or destroying faraway targets immediately. However, because of the atmospheric effect, the ability of the HEL to focus on the target can be significantly degraded. For improved focus on the target, this atmospheric effect should be accurately analyzed and mitigated in the HEL. Atmospheric turbulence and thermal blooming have been studied for decades to maximize the efficiency of the HEL. The aim of this study is to maximize the efficiency of the HEL through an accurate analysis of the atmospheric effects and mitigation using adaptive optics (AO). An accurate analysis of the HEL’s beam propagation through the atmosphere is implemented based on the split-step beam propagation method, and the phase correction of atmospheric distortions, such as turbulence and thermal blooming, is simulated using an AO simulation tool that is independently developed by LIG Nex1. The result of the simulation of the split-step beam propagation showed a high accuracy compared with the analytical result of beam diffraction without atmospheric turbulence. Furthermore, that result confirmed that atmospheric distortions could be effectively mitigated using the AO system in the phase correction simulation.

Air gun arrays are often used in marine energy exploration and marine geological surveys. The study of the single bubble dynamics and multibubbles produced by air guns interacting with each other is helpful in understanding pressure signals. We used the van der Waals air gun model to simulate the wavelets of a sleeve gun of various offsets and arrival angles. Several factors were taken into account, such as heat transfer, the thermodynamically open quasi-static system, the vertical rise of the bubble, and air gun post throttling. Marine vertical cables are located on the seafloor, but hydrophones are located in seawater and are far away from the air gun array vertically. This situation conforms to the acquisition conditions of the air gun far-field wavelet and thus avoids the problems of ship noise, ocean surges, and coupling. High-quality 3D wavelet data of air gun arrays were collected during a vertical cable test in the South China Sea in 2017. We proposed an evaluation method of multidimensional facial features, including zeropeak amplitude, peak-peak amplitude, bubble period, primary-to-bubble ratio, frequency spectrum, instantaneous amplitude, instantaneous phase, and instantaneous frequency, to characterize the 3D air gun wave field. The match between the facial features in the field and simulated data provides confidence for the use of the van der Waals air gun model to predict air gun wavelet and facial features to evaluate air gun array.

We investigated the strengthened ocean surface heat flux at Ieodo Ocean Research Station (Ieodo ORS) during the passage of Typhoon Lingling. On September 6, 2019, when Typhoon Lingling approached the Ieodo ORS, we observed a dramatic drop in the sea surface temperature (SST) of 5.0 °C along with intense turbulent mixing. Although the decline of the SST was much weaker than the observed data, the SST simulated by the regional air-sea coupled model exhibited a decrease of about 2.0 °C in a few hours due to turbulent mixing by current shear. At the same time, the latent heat flux showed a robust downward transfer. We also investigated the case with the air-sea coupled model and atmosphere-only model, but this negative latent heat flux was not captured. The sensible heat flux was better captured by the coupled model than the uncoupled model. And the coupled model simulated the latent heat flux closer to downward than the uncoupled model. We conducted a sensitivity test by altering the flux estimation methods used to estimate ocean heat fluxes. We found that the latent heat flux was more sensitive to the choice of estimation and showed much room for improvement. In this regard, the joint model-observation study using Ieodo ORS data provides an invaluable opportunity for improved typhoon simulation.

Wind is a stochastic and intermittent renewable energy source. Due to it’s nature, it is extremely hard to forecasting of wind power. Accurate wind power forecasting can be encouraging and motivating for investors to shed light on future uncertainties caused by global warming. Thus, CO2 and other greenhouse gases which are harmful to the environment will not be released into the atmosphere, while generating electrical energy. This paper presents a novel precise, fast and powerful hybrid metaheuristic wind power forecasting approach based on statistical and mathematical data from real weather stations. The model was developed as a hybrid metaheuristic algorithm based on Artificial Neural Networks (ANNs), Particle Swarm Optimization (PSO) and Radial Movement Optimization (RMO). Real-time wind data was gathered from Wind Measuring Stations (WMS) at two separate places in Burdur and Osmaniye cities, Turkey. The key contribution of this new model is the ability to perform wind power forecasting studies, without needing wind speed data, with high accuracy and rapid solutions. Also, it has been carried out wind power forecasting studies with high accuracy despite the height differences between the sensors. That is, for WMS-1 and WMS-2, it has succeeded the wind power forecasting at 61m and 60.3m using temperature (3m), humidity (3m), and pressure (3.5m) data. The performance results were presented in tables and graphs.

Full scale experiment has received increasing attention in recent years for the reliability analysis of power supplies and power systems. In this paper, the vibration behaviours of conductors with and without D-section ice coatings are addressed by virtue of a field test platform consisting of the prototype of a transmission tower-line system. Utilizing fibre Bragg grating sensors, the vibration of conductors under artificial displacement and natural wind excitations are monitored, and their dynamic characteristics are assessed by the spectral analysis and the identification technique of Hilbert-Huang transform. It is revealed that the vibrations of ice-free and ice-coated multi-bundled conductors vary wildly despite under similar artificial displacements and natural wind excitations. The vibration of ice-coated conductors is mainly dominated by their low-order modes, especially in the frequency range of 0.24–2.0 Hz; while the vibration of ice-free conductors gains more benefits from their high-order modes. Compared to the ice-free conductors, the conductors with eccentric ice coating are prone to suffer from galloping under specified wind attack angle; although their vibrations are still controlled by the low-order modes, yet the frequency values of the dominant modes have changed from one wind attack angle case to another. This kind of frequency modulation phenomenon indicates that nonlinear vibration characteristics of ice-coated conductors might change under different wind conditions, which brings great challenges to the research of wind-induced vibration characteristics of ice-coated conductors.

A building complex consisting of four identical long-span roof structures are tested in the wind tunnel to determine dynamic wind loads on structures. Based on the time-history data of spatially distributed wind pressure, wind-induced vibration analyses of the structures under varying incident wind attack angles have been carried out in time-domain. Then a novel framework for assessing dynamic wind resistance reliability has been proposed by integrating wind tunnel experiment, Monte Carlo simulation method, and the non-Gaussian wind pressure field simulation technique. The framework takes into account the uncertainties of design wind speed, wind directionality and structural damping ratio, as well as the randomness of Non-Gaussian wind pressure field. It has been demonstrated that the proposed framework is effective and efficient to comprehensively assess the wind-induced dynamic reliability of the long-span roof structure in the rectangular array. The annual failure probability of the long-span roof structure is obtained by considering the first passage reliability of displacement responses.

Previous numerical studies have focused on the combined effect of momentum and scalar eddy diffusivity on the intensity and structure of tropical cyclones. The separate impact of eddy diffusivity estimated by planetary boundary layer (PBL) parameterization on the tropical cyclones has not yet been systematically examined. We have examined the impacts of eddy diffusion of moisture on idealized tropical cyclones using the Advanced Research Weather Research and Forecasting model with the Yonsei University PBL scheme. Our results show nonlinear effects of moisture eddy diffusivity on the simulation of idealized tropical cyclones. Increasing the eddy diffusion of moisture increases the moisture content of the PBL, with three different effects on tropical cyclones: (1) an decrease in the depth of the PBL; (2) an increase in convection in the inner rain band and eyewall; and (3) drying of the lowest region of the PBL and then increasing the surface latent heat flux. These three processes have different effects on the intensity and structure of the tropical cyclone through various physical mechanisms. The increased surface latent heat flux is mainly responsible for the decrease in pressure. Results show that moisture eddy diffusivity has clear effects on the pressure in tropical cyclones, but contributes little to the intensity of wind. This largely influences the wind-pressure relationship, which is crucial in tropical cyclones simulation. These results improve our understanding of moisture eddy diffusivity in the PBL and its influence on tropical cyclones, and provides guidance for interpreting the variation of moisture in the PBL for tropical cyclone simulations.