Atmospheric and Oceanic Optics最新文献

Disturbances in the near-Earth environment are accompanied by disruptions in ground-based and satellite technological systems, including catastrophic failures. Therefore, the problem of developing methods for real-time analysis and monitoring of the natural environment with an acceptable accuracy becomes particularly pressing. This paper presents a new automated method for detecting and estimating anomalies in neutron monitor (NM) observations. This method is based on the synthesis of wavelet decompositions with the rules of statistical decision theory; it enables the detection of anomalies in NM observations and estimation of their intensity. Discrete wavelet decompositions with adaptive threshold functions are used to detect anomalies. Parameters of the threshold functions are automatically estimated (as the data enter the processing system) using rules of statistical decision theory. Applying these rules yields a solution with an error not exceeding an a priori specified value. The intensity of anomalies in NM observations is then calculated by summing the amplitudes of wavelet coefficients exceeding the estimated thresholds. The paper studies periods of strong and extreme geomagnetic storms in 2024–2025. Correlations between values of the Dst index and the intensity of anomalies in NM observations are analyzed. The results show a significant increase in the correlation during geomagnetic storms. The Dst index reached its maximums relative to the intensity maximums with a delay of several hours, which demonstrates the importance of neutron monitor observations and their consideration when solving space weather problems. The results of the work can be used in space weather forecasting for the early detection of sporadic variations in the cosmic ray flux.

The profound study of the spatial distribution of aerosol sources is essential for understanding their impact on air quality and public health. The source fields of various atmospheric aerosol types arriving to the Middle Urals were estimated from the analysis of the potential source contribution function. Data on the aerosol type classified by spectral values of atmospheric aerosol optical depth were taken as initial. The results show a clear spatial differentiation of atmospheric aerosol sources for “dust” and “elevated smoke” classes. The suggested approach can significantly supplement the information provided by ground-based spectral photometric measurements, thus improving the accuracy of air quality assessments.

Solar thermal tides significantly impact global atmospheric circulation. Being a key factor of the dynamic relationship between atmospheric layers, tides ensure the distribution of the effect of changing solar forcing over all atmospheric layers. Therefore, it is important to study different external factors which can influence solar thermal tide generation and propagation throughout the atmosphere. Using the mechanistic nonlinear numerical general circulation model of the middle and upper atmosphere (MUAM), we examine the influence of variations in solar activity (SA) on the spatiotemporal structure of tides. Two ensembles of MUAM simulations of the global atmospheric circulation in January are considered, each consisting of 16 runs corresponding to high and low SA. An increase in solar forcing at high SA weakens diurnal migrating tide DW1 in the altitude range 100–150 km and intensifies it at higher altitudes. The analysis of the Eliassen–Palm (EP) fluxes shows a significant correlation between changes in the vertical propagation of wave activity and DW1 amplitude: downward flux increments generally correspond to tide weakening in the altitude range 110–150 km, while upward flux increments correspond to tide strengthening above 150 km. Semidiurnal migrating tide SW2 weakens at high SA at altitudes of up to 140 km in the Southern Hemisphere and 190 km in the Northern Hemisphere in the mid- and high-latitude thermosphere. This is mainly accompanied by weakening of the upward EP fluxes. Above 200 km, SW2 amplitude increases by a factor of two to three at high SA in the Northern Hemisphere. Above 150 km in the thermosphere, the amplitude of stationary planetary wave with zonal wavenumber 1 (SPW1) decreases at high SA, while the amplitude of the migrating tides increases. Together, these result in a complex structure of changes in the amplitudes of non-migrating tides. Understanding the complex mechanisms of dynamic interactions between tides and atmospheric circulation is important for improving numerical forecasts of changes in atmospheric processes on different time scales, from days to decades.

To mitigate channel-induced degradation in underwater wireless optical communication (UWOC), this study combines theoretical and experimental analyses to characterize 488 nm blue OAM beam propagation across varying temperatures, salinities, and distances. Under short-range conditions, received power decreases monotonically with increasing temperature (10 ∼ 30°C) and salinity (10 ∼ 35 PPT), though overall attenuation remains modest. Notably, salinity fluctuations exerted a more pronounced impact (0.167%/PPT) than temperature (0.023%/°C). Transmission distance is a key factor driving exponential power loss and quality degradation, with an average relative loss of 11.1%/m due to cumulative water attenuation and reflective losses. Furthermore, transmission efficiency proved highly mode-dependent: lower-order modes (l = 1) exhibited superior robustness and stability over higher-order modes (l ≥ 3), owing to their reduced diffraction divergence and compact energy distribution. These findings provide critical theoretical and experimental guidance for modal selection and link design in UWOC systems.

The main problem in solar energy is reducing optical losses due to light reflection from the surface of photovoltaic cells. This paper numerically studies antireflection properties of nanostructured silicon dioxide (SiO₂) coatings deposited on the surface of a solar cell. Two porous antireflection coating types are considered: multilayer assembly of nanospheres and vertical air nanopores embedded in a solid SiO₂ layer. The light transmission efficiency is assessed depending on the coating thickness and structure. It is found that the efficiency of solar energy conversion into electricity can significantly vary across different spectral ranges for the same antireflection coating type. It is shown that a coating in the form of vertical nanopores in most cases provides more efficient conversion of incident light compared to a porous layer assembled of nanospheres. The results are important for designing more efficient solar cells and can be used to create antireflection coatings to improve the overall performance of photovoltaic devices.

Chloroform is one of dangerous air pollutants. To control it in the atmosphere by absorption spectroscopy, it is necessary to know the position of its spectral lines. In this work, the absorption spectra of CH³⁷Cl₃ isotopologue of gaseous chloroform are measured using a high-resolution nonstationary spectrometer in the frequency range 118–175 GHz, where spectroscopic data for this compound are absent. The identification of the chloroform lines presented in the literature and assigned to the vibrational state ν₂ of CH³⁵Cl₃ is refined; their belonging to CH³⁷Cl₃ isotopologue is shown. The experimental results are compared with our theoretical estimates of absorption line centers of the rotational spectrum of this molecule in the same spectral range. Absorption lines of CH³⁷Cl₃ isotopologue in the ground state were detected and identified in the spectral subranges near 131.4, 137.6, 150.1, and 156.4 GHz. Based on the experimental spectra, we have estimated the molecular constants B = 3129.56 MHz, D_J = 1.34 kHz, and D_JK = −2.25 kHz with RMSE = 7.84 × 10⁻² MHz, which determine transition frequencies in absorption spectra near 150.1 and 156.4 GHz more accurately than molecular constants given in the literature (B = 3129.61 MHz, D_J = 1.37 kHz, and D_JK = −2.28 kHz with RMSE = 11.55 × 10⁻² MHz). The results can be used for controlling the atmospheric content of chloroform.

The paper theoretically studies the propagation regimes of narrow (millimeter) laser beams in a Kerr-nonlinear turbulent medium, which simulates the evolution of light inhomogeneities generated under multiple filamentation of high-power laser pulses in corresponding media, by methods of diffraction-beam tubes and diffraction rays. Three propagation regimes are found: self-focusing with generation of a nonlinear focus (beam collapse), self-channeling over a limited distance, and turbulent propagation. An equation for squared beam effective radius is derived, which is of interest for practical applications in nonlinear atmospheric optics.

Detection of coordinates and magnification of a reconstructed holographic image of a particle is quite difficult because of the lack of a strict geometric-optical model of digital holographic imaging. Traditional optics and microscopy usually use lenses for image magnification. In digital holography, magnified images can be generated without mechanical focusing and optical components, for example, by controlling the divergence of illuminating beams. This work discusses optimization of the optical scheme of digital holography for lensless magnification of reconstructed images; justifies the feasibility of using a geometric-optics apparatus in the design of digital holographic systems, and describes their limitations. The results of the work can be used in the design and development of digital holographic microscopy systems and for high-precision reconstruction and analysis of holographic images of particles.

Most measurements of aerosol attenuation of the atmosphere are carried out in the visible and near-infrared regions of the spectrum. However, many atmospheric optics tasks require data on the spectral behavior of aerosol extinction coefficients in the visible and IR regions, including the atmospheric “transparency window” 8–12 μm. In this regard, models that make it possible to calculate attenuation in the IR region based on measurements in the visible region are of great interest. A one-parameter model of the spectral behavior of the aerosol extinction coefficient for the surface air layer is suggested. The input parameter of the model is the aerosol extinction coefficient at a wavelength of 0.55 μm or the meteorological visibility range S_m. The model enables one to calculate the mean aerosol extinction coefficient in the wavelength range 0.44–12 μm at meteorological visibility range S_m > 8 km. The model can be used to evaluate the efficiency of different optical systems and to separate aerosol attenuation into submicron and coarse components.

The analysis of a spectrum of ¹⁵N¹⁸O molecule recorded in the region 5100–5500 cm⁻¹ was performed, and 187 positions of rotational lines were found in the vibrational band 3–0 of the main transitions between the electronic states ²Π_1/2 and ²Π_3/2 with the maximal rotational quantum number J = 32.5. For the first time, Λ-splitting was observed in this band. The positions and relative intensities of both the resolved component of Λ-doublets and unresolved doublets were determined. A joint weighted processing of all known vibrational-rotational transition frequencies in the microwave and infrared spectral regions was carried out. As a result, Dunham type constants were determined for ¹⁵N¹⁸O isotopologue in the ground electronic state. Using the found constants, predictive calculations of the rotational line positions of all bands corresponding to vibrational transitions between states with ({v}) ≤ 3 and J ≤ 37.5 were carried out. The experimental data obtained in this study provide new spectroscopic information about ¹⁵N¹⁸O isotopologue and enrich fundamental knowledge about nitrogen monoxide molecule.