Home – Home – Jornals – Atmospheric and Oceanic Optics 2025 number 11

It is quite difficult to determine the coordinates and magnification of reconstructed holographic image of a particle due to the lack of a clear geometrical-optical model describing the digital holographic process. To obtain magnified images in traditional optics and microscopy, lenses are usually used. In digital holography, such images can be formed without mechanical focusing and the use of optical components, for example, by controlling the divergence of illumination beams. This paper considers the issues related to the optimization of the optical scheme of digital holography that ensures lensless magnification of reconstructed images, justifies the feasibility of using a geometric optics apparatus in the design of such 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, for high-precision reconstruction and analysis of holographic images of particles.

In this work, the analysis of the recorded spectrum of the ¹⁵N¹⁸O molecule in the region 5100-5500 cm^-1 was performed. As a result of the analysis, 187 positions of rotational lines 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 were found. For the first time, Λ-splitting was observed in this band. The positions and relative intensities of both the resolved component of the Λ-doublets and unresolved doublets are determined. A joint weighted processing of all known vibrational-rotational frequencies of the transitions in the microwave and infrared spectral regions was carried out. As a result of the processing, “Dunham-type" constants for ¹⁵N¹⁸O isotopologue in the ground electronic state were determined. Using the found “Dunham-type" 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.

Chloroform is one of dangerous pollutants in the atmosphere. 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 v₂ for CH³⁵Cl₃ is refined and their belonging to CH³⁷Cl₃ isotopologue is shown. The experimental results are compared with our theoretical estimates of absorption lines 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 parts near 150,1 GHz 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 content of chloroform in the atmosphere.

The main problem in solar energy is reducing optical losses due to light reflection from the surface of photovoltaic cells. This paper presents the results of a numerical study of antireflection properties of nanostructured silicon dioxide (SiO₂) coatings deposited on the surface of a solar cell. Two types of porous antireflection coatings are considered: a multilayer assembly of nanospheres and vertical air nanopores embedded in a continuous silicon dioxide layer. The light transmission efficiency is assessed depending on the thickness and structural design of the antireflection coating. 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 made of vertical nanopores in most cases provides more efficient conversion of incident light compared to a porous layer formed by an ordered microassembly of nanospheres. The results are important for the development of more efficient solar cells and can be used to create anti-reflective coatings to improve the overall performance of photovoltaic devices.

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 course of aerosol attenuation coefficients in the visible and IR regions, including the atmospheric “transparency window” 8-12 mm. 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 course of the aerosol attenuation coefficient for the surface layer of the atmosphere is proposed. The input parameter of the model is the aerosol attenuation coefficient at a wavelength of 0.55 mm or the meteorological range of visibility S _m. The model enables one to calculate aerosol attenuation coefficient in the spectral range 0.44-12 mm 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.

Natural gamma radiation easily penetrates into the cells of a human body and destructively affects all structures causing a wide range of diseases. It also plays an active role in the atmosphere by participating in electrical processes and origination of ions, which affects cloud formation, precipitation, radiation balance, etc. There are very few measurements of the vertical distribution of gamma background over the Russian territory. This paper summarizes the results of aircraft sounding in 2003-2025. Based on the analysis of the long-term data, an average vertical profile of this parameter was calculated, which shows its nonlinear increase with altitude. In the surface air layer, this parameter varied within 0.03-0.25 mSv/h with the average over the period under study being 0.11 mSv/h. At an altitude of 10 km, the gamma background varied in the range 2.18-2.80 mSv/h, and the average was 2.35 mSv/h. The analysis of the latitudinal distribution revealed the belt 60-70° N with high gamma radiation values; the gamma background was lower to the south and north of that belt The data analysis has also revealed a weak annual variation with a maximum in November and a minimum in August, which is not typical for other atmospheric parameters. The results can be useful for choosing the range and uncertainty of developed radiation protection devices and means, as well as for assessing the probability of origination of radiative effects.

Stratospheric polar vortices, which form over the polar regions in late autumn, are large-scale cyclonic formations whose stability in the winter-spring period determines the scale and depth of spring ozone depletion. Using the vortex delineation method based on ERA5 reanalysis data, we studied the features in the vertical dynamics of the Arctic and Antarctic polar vortices in 2020 during their anomalous strengthening, which was accompanied by deep and prolonged ozone depletion in the Arctic and Antarctic. In particular, we examined the synchronicity in temporal changes at different stratospheric levels. The polar vortex breakdown in 2020 was observed from late spring to early summer spreading from top to bottom over 1-2 months. The dynamics of the Arctic polar vortex showed three peaks of activity, spreading from the upper to the lower stratosphere within a month. The dynamics of the Antarctic polar vortex clearly showed one peak of activity spreading from the upper to the lower stratosphere over a period of 2 months. The anomalous duration of the western phase of the quasi-biennial oscillation in the middle stratosphere has been proposed as a possible reason for the unprecedented strengthening of the polar vortices in 2020. The results can be used to assess the risks of increasing ground-level UV-B radiation which is dangerous for the biosphere.

The objective of this study was to determine an optimal radiation wavelength for scanning marine surface from air, which provides minimal radiation absorption, parasitic fluorescence, beam divergence, and scattering in the water column. These parameters depend on the probing laser type used. The research focused on water samples from the Black Sea collected 200 m from the shore immediately before the experiment and water samples stored for one year in light-protected hermetically sealed containers. For both sets of samples, the following were examined: scattering phase function, spectral transmission coefficients, laser beam divergence, particle size distribution of organic matter in the samples, and its effect on fluorescence spectra. Commercial semiconductor lasers with wavelengths of 450, 520, and 660 nm were used. The study shows a 450-nm laser to be optimal for underwater probing tasks since it exhibits the lowest radiation attenuation in the water column (0.5 dB/m), the smallest scattering spot, and minimal fluorescence. Organic particles do not significantly affect hydro-optical properties of seawater in the samples both immediately collected before the experiment and stored for one year. The results can be used in the design of above-water and underwater laser probing systems for marine surface analysis.

To perform accurate atmospheric correction (elimination of the distorting influence of the atmosphere) of satellite images, it is crucial to consider various factors that influence the received signal, including the non-Lambertian surface reflectance (the difference between surface reflection and Lambert's law, according which radiation is equally reflected in all directions and depends only on the irradiance of the surface and the reflectance). High-quality satellite information is important for solving a wide range of problems in monitoring the ground surface, such as forest condition, agricultural productivity, and others. In some algorithms, non-Lambertian reflection is taken into account after solving the problem in the Lambertian reflection approximation. In this case, the assumption is used that the adjacency effect (received radiation reflected from areas of the ground surface adjacent to the observed one and scattered in the atmosphere) is formed only by surfaces with Lambertian reflection. The calculations performed show that at S _M ≥ 6 km, neglect of non-Lambertian reflection produces an error in determining the reflectance of no higher than 20.3%, neglect of non-Lambertian reflection in the formation of adjacency effect and additional illumination results in an error of no more than 12%, and neglect of non-Lambertian reflection in additional illumination, of no more than 1.4%. For more clear situations ( S _M ≥ 6 km), the maximal error for similar models does not exceed 92, 14, and 1.2%, respectively. For solar zenith angles θ_sun ≤ 60° and angles of the optical axis of the receiving system θ_sun ≤ 60°, the errors do not exceed 30, 7.5, and 1%, respectively. The results prove the possibility of considering non-Lambertian reflection after taking into account adjacency effect and additional illumination of the ground surface in the Lambertian reflection approximation.

Interest in understanding the influence of forest ecosystems on the formation of climate parameters continues to grow. This paper examines two approaches to the study of interaction between Siberian forests and the atmosphere. Based on the results of the analysis, it was suggested that the formation of a 4-year cycle in precipitation over forest areas may occur with the participation of tree transpiration. This finding will help us to understand the emergence of similar cyclical patterns in meteorological data from other regions with extensive forest ecosystems. The results may be useful for specialists dealing with problems of biosphere-atmospheric interaction.

A dielectric mirror with high reflectance at a wavelength of 266 nm has been designed for use in ultraviolet lidar systems for ozone concentration monitoring. A multilayer interference coating based on HfO₂ and SiO₂ was manufactured and optimized using experimentally obtained dispersion data. The effect of thermal annealing on the optical properties of the coating was investigated, and a temperature limit was identified, excess of which leads to structural degradation. The results can be used in the design of highly efficient optical elements for ultraviolet differential absorption lidars, as well as other laser systems which require UV dielectric mirrors.

It is known that the formation of vortex structures in a fire negatively impacts the consequences: swirling high-temperature flows of combustion products cause greater destruction than a normal fire. Identifying such vortices is a pressing issue. For this purpose, in the big aerosol chamber of the Institute of Atmospheric Optics SB RAS, two isopropanol flame plumes were simultaneously studied by the thermal imaging method. One of them was a vortex flame obtained by blowing around a stationary container installed on the axis of an ascending swirling air flow, and the other was in a container without blowing. Using the fast Fourier transform (FFT) of the time pulsations of the thermal imaging signal, the power spectra of the pulsation frequencies were calculated. In the calculated spectra, a frequency interval was determined where a significant difference between the mentioned flames was observed. The influence of distance and the averaging effect of the size of the initial region of thermal imaging signal reception on the difference in flame spectra was analyzed.