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On the basis of data from 8 aerological stations: St. Petersburg, Tallinn, Sukhinichi, Bologoye, Velikiye Luki, Smolensk, Ryazan and Dolgoprudny, the variability of the refractive index vertical profile in the troposphere is shown. It is noted that the presence in the troposphere of inversions of the altitudinal temperature profile and narrow zones with increased and decreased water vapor content leads to sharp changes in the index refractive index gradient and determines the type of radio wave refraction.

The ultrashort radio wave refraction in the troposphere depends on meteorological conditions. In the present study, an atmospheric-soil measuring complex is used to measure the meteorological parameters at altitudes of 1 and 10 m for three years (2015–2017), and refraction gradients are calculated at standard meteorological times. Monthly datasets are grouped depending on the time of day to illustrate their typical diurnal behavior. The obtained data sub-arrays are analyzed using descriptive statistics. The occurrence of super-refraction is observed in the second half of day at the lake coast during the summer period.

We consider the problem of eliminating the effect of multipath radio wave propagation in inhomogeneous plasma media by additional spatial processing of field measurements. This field processing is based on the Double Weighted Fourier Transform (DWFT). The calculations are made for cases of multipath propagation due to radio wave refraction by plasma focusing and defocusing lenses for ionospheric and laboratory plasma scales. It has been shown that images of plasma irregularities can be reconstructed with high resolution using the DWFT spatial processing for circular field measurements under multipath propagation of radio waves. Comparative analysis of the results obtained from spatial field processing by the inverse DWFT method and the Fresnel inversion is performed.

Reflection and refraction of waves occur at the interface between two different media. These two fundamental interfacial wave phenomena form the basis of fabricating various wave components, such as optical lenses. Classical refraction—now referred to as positive refraction—causes the transmitted wave to appear on the opposite side of the interface normal compared to the incident wave. By contrast, negative refraction results in the transmitted wave emerging on the same side of the interface normal. It has been observed in artificial materials 1 – 5 , following its theoretical prediction 6 , and has stimulated many applications including super-resolution imaging 7 . In general, reflection is inevitable during the refraction process, but this is often undesirable in designing wave functional devices. Here we report negative refraction of topological surface waves hosted by a Weyl phononic crystal—an acoustic analogue of the recently discovered Weyl semimetals 8 – 12 . The interfaces at which this topological negative refraction occurs are one-dimensional edges separating different facets of the crystal. By tailoring the surface terminations of the Weyl phononic crystal, constant-frequency contours of surface acoustic waves can be designed to produce negative refraction at certain interfaces, while positive refraction is realized at different interfaces within the same sample. In contrast to the more familiar behaviour of waves at interfaces, unwanted reflection can be prevented in our crystal, owing to the open nature of the constant-frequency contours, which is a hallmark of the topologically protected  surface states in Weyl crystals 8 – 12 . Sound waves in a specially designed crystal undergo ‘topologically protected’ negative refraction, whereby no reflection is allowed, at certain facets of the crystal and positive refraction at others.

The radio-wave refraction error caused by the troposphere and ionosphere badly affects accuracy in terms of the navigation, positioning, measurement, and control of a target; it is the main source of errors in high-accuracy measurement and control systems. The high-accuracy technology needed for radio-wave refraction error correction (mainly in the troposphere and ionosphere) has been the focus of research for a long time. At present, the correction methods used for radio-wave refraction errors have a low accuracy. For an S-band radio-wave signal, the accuracy of refraction error correction can generally only reach m-level (elevation angle of 15° and above), and thus has difficulty meeting the requirements of dm-level accuracy refraction error correction for deep-space and high-orbit targets. To improve the accuracy of radio-wave refraction error correction for deep-space and high-orbit targets, a novel correction method for tropospheric and ionospheric range error due to refraction is proposed in this study, on the basis of the measured data from a water vapor radiometer and dual-frequency Global Navigation Satellite System (GNSS). The comprehensive calibration test is conducted in combination with the Chinese Area Positioning System (CAPS) in Kunming. Results show that this method can effectively correct the range error due to refraction that is caused by the troposphere and ionosphere. For an S-band radio-wave signal, the accuracy of refraction error correction can reach dm-level accuracy (elevation angle of 15° and above), which is 50% higher than that achieved with traditional methods. This work provides an effective support system for major projects, such as lunar exploration and Mars exploration.

Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat's principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.

An advanced numerical model is presented for the simulation of wave-induced free-surface flow, utilizing an efficient hybrid parallel implementation. The model is based on the solution of the Navier–Stokes equations using large-eddy simulation of large-scale coastal free-surface flows. The three-dimensional immersed boundary method was used for the enforcement of the no-slip boundary condition on the bed surface. The water-air interface was tracked using the level-set method. The numerical model was effectively validated against laboratory measurements involving wave propagation over a flatbed with an elliptical shoal, whose presence induces combined wave refraction and diffraction phenomena. The parallel implementation of the model enabled the efficient simulation of depth-resolved, wave-induced, three-dimensional, free-surface flow; the model parallel efficiency and strong scaling are quantitatively demonstrated.

Polarization is one of the basic properties of electromagnetic waves conveying valuable information in signal transmission and sensitive measurements. Conventional methods for advanced polarization control impose demanding requirements on material properties and attain only limited performance. We demonstrated ultrathin, broadband, and highly efficient metamaterial-based terahertz polarization converters that are capable of rotating a linear polarization state into its orthogonal one. On the basis of these results, we created metamaterial structures capable of realizing near-perfect anomalous refraction. Our work opens new opportunities for creating high-performance photonic devices and enables emergent metamaterial functionalities for applications in the technologically difficult terahertz-frequency regime.

A plasmonic antenna array is used to control the propagation of a light beam across an interface. The precise manipulation of a propagating wave using phase control is a fundamental building block of optical systems. The wavefront of a light beam propagating across an interface can be modified arbitrarily by introducing abrupt phase changes. We experimentally demonstrated unparalleled wavefront control in a broadband optical wavelength range from 1.0 to 1.9 micrometers. This is accomplished by using an extremely thin plasmonic layer (~λ/50) consisting of an optical nanoantenna array that provides subwavelength phase manipulation on light propagating across the interface. Anomalous light-bending phenomena, including negative angles of refraction and reflection, are observed in the operational wavelength range.

Mesoscale eddy currents influence ocean surface waves, but their imprints on wave height remain poorly described by observations. Here, we examine significant wave height (SWH) variations associated with more than 42,000 mesoscale eddies in the Southern Ocean using along‐track Jason‐3 altimeter measurements. Altimeter composites reveal a pronounced meridional dipole, with reduced SWH where wave propagation aligns with eddy currents and enhanced SWH on the opposing side. Typical eddies (radius ∼45 km, geostrophic velocity anomalies ∼0.15 m s−1) are associated with SWH anomalies of ∼5 cm. Reanalysis data and idealized simulations further suggest that eddy‐related wind anomalies, the relative wind effect and direct current effects all contribute to the observed SWH patterns, with refraction playing a key role. These results highlight the role of mesoscale currents in redistributing wave energy and shaping the spatial distribution of wave height.