Home – Home – Jornals – Atmospheric and Oceanic Optics 2025 number 5

Quantitative analysis of the gas mixture absorption spectra is complicated by noise. The parameters of standard filters are related to the entire analyzed spectral range. This means that the filter parameters being optimal for strong absorption lines are not optimal for weak absorption lines and vice versa. An approach to create adaptive filter for denoising experimental spectra based on the combination of a windowed version of a standard filter with the independent component analysis is suggested and implemented with the Savitzky-Golay filter as an example. The numerical simulation was carried out at normal conditions for the absorption spectra of the model of mid-latitude summer atmosphere in the 100-1000 GHz spectral range. The efficiency of the suggested adaptive and the standard versions of Savitzky-Golay filter was compared using a quantitative criterion of the proximity between two spectral curves. Experimental validation of efficiency of the suggested adaptive Savitzky-Golay filter was conducted on the example of 200 ppm SO₂ and 10000 ppm H₂O gas mixture. The SO₂ concentration was evaluated using multivariate curve resolution method. The relative error in the concentration retrieved after noise reduction by this filter was 3.7 times less compared to the standard Savitzky-Golay filter. Thus, the suggested adaptive Savitsky-Goley filter makes it possible to increase the efficiency of noise suppression in experimental spectral data.

The paper presents the results of calculating 10 the lowest vibrational energy levels of all 24 stable sulfur dioxide isotopologues. The calculations were performed using the ab initio potential energy function of the main isotopologue ³²S¹⁶O₂, the Rayleigh-Schrödinger perturbation theory of high orders and the Padé-Hermite series summation method. A numerical analysis of the series was performed, which showed that the perturbation series monotonically converge, but to obtain the energy levels of some vibrational states with an error of less than 1.0 cm^-1, it is necessary to take into account the corrections of the 3rd-6th orders. The quadratic Padé-Hermite approximants give energy levels that coincide with high accuracy with the results of numerical diagonalization of the Hamiltonian matrix. A correction is proposed for calculating isotopic shifts, which gives a root-mean-square coincidence of 1.1 cm^-1 with the experimental and calculated data by other authors. The calculation results can be used to solve various problems of atmospheric spectroscopy, astrophysics, geochemistry, and other fields of science related to the analysis of spectra of isotope-substituted molecules.

Atmospheric turbulence is one of the most significant factors affecting the propagation of waves of various nature and the operation of devices based on their application. The paper presents the results of experimental studies of the impact of short-term heavy rainfall on subsequent changes in the meteorological and turbulent state of the ground atmosphere based on processed synchronous acoustic and optical measurements of atmospheric parameters. An assessment is made of the impact of intense precipitation on the main turbulent characteristics of the surface atmosphere, such as the energy of temperature and wind fluctuations and vertical heat and momentum fluxes. It is shown that heavy rainfall significantly changes these characteristics. The results can be used to interpret optical and acoustic measurements used to study the atmosphere.

Observations of the state of the mesosphere of Venus from spacecraft have not yet revealed transient luminous events similar to those observed in the Earth's atmosphere. In this work, a possibility of such phenomena is proved in laboratory conditions. For this purpose, an experiment was conducted on the formation of apokamps in carbon dioxide at various pressure values. The results confirm the hypothesis that conditions at altitudes corresponding to the upper edge of clouds in the atmosphere of Venus are favorable for the generation of analogues of transients of the Earth's mesosphere. Based on this, recommendations have been developed for the design of detection systems for such phenomena from orbiting satellites or balloons.

Based on a developed and adapted method for identifying Rossby wave breaking (RWB), which accounts for the specifics of stratospheric circulation, an analysis of the conditions for the occurrence of major sudden stratospheric warmings (SSWs) in the Northern Hemisphere was conducted. The method relies on examining the geometry of potential vorticity contours in the stratosphere at the 850 K level using ERA5 reanalysis data. It is shown that anomalous RWB processes in November and December play a key role in preparing for the onset of SSWs. Most of the analyzed SSW events are associated with an increase in the number of RWB events in the Asia-Pacific (AP) region in November and December, and occasionally in January. In cases where SSW initiation is linked to RWB over the Atlantic and Europe, it is also preceded by RWB anomalies in the AP region. For the identified types of wave breaking in the stratosphere, atmospheric blocking is characteristic in the troposphere, accompanied by negative near-surface temperature anomalies over Eurasia and/or North America. The increased frequency of early and middle major SSW events aligns with the previously identified trend of enhanced negative temperature responses to atmospheric blocking in the Northern Hemisphere.

The development of the deep underwater neutrino telescope BAIKAL-GVD involves the creation of equipment for regular long-term monitoring of inherent optical properties (IOP) of the aquatic environment within the effective volume of the telescope. Regular monitoring of IOP not only allows increasing the accuracy of retrieving neutrino energy and direction, but also provides unique data for limnological studies. The article describes the design of the BAIKAL-5D devices developed to solve this problem and considers the methods and algorithms for in situ monitoring of IOP used in these devices. The sources of instrumental error in measuring the absorption and scattering of light in water are investigated and the necessary corrections are determined. Some results of measuring IOP of the deep waters of Lake Baikal using BAIKAL-5D devices are presented.

This paper demonstrates for the first time the possibility of exciting anti-Stokes fluorescence of PO-fragments of organophosphates. Using the example of drop-liquid traces of triethyl phosphate on a paper surface, it was determined that the relative population of vibrational levels v '' = 1 and v '' = 2 corresponds to a vibrational temperature of fragments of about 780 K. Indicators of significant violation of the equilibrium distribution of fragments over rotational energy levels were revealed. It has been determined that the method of exciting anti-Stokes fluorescence of PO-fragments of triethyl phosphate from the first vibrational level of the ground state X ²Π ( v '' = 1) to the zero vibrational level of the electronically excited state A ²Σ⁺ ( v ' = 0) provides the highest noise immunity of the LF/LIF method. The results can be used to select the optimal technique for exciting fluorescence of PO-fragments when implementing the LF/LIF method for remote detection of organophosphate traces.

The paper is devoted to research of the output signal composition of metal-vapor laser active optical systems under various operating conditions. The effect of the temporal characteristics of laser active optical systems on the output signal composition is experimentally estimated. The method for determining the contribution of amplified spontaneous emission (ASE) to the output signal of self-adjoint scheme and scheme with independent illumination source is suggested. The optimal time when input signal enters to active medium of amplifier for providing maximal signal/noise ratio is determined. ASE is completely suppressed at a time delay of (-4.3; +25.8) ns in the scheme with independent illumination source. It is impossible to achieve complete suppression for the self-adjoint scheme. The minimal ASE value in the self-adjoint scheme was 80 mW, i.e., approximately 2% of the output signal power. The results can be useful in researching the amplification characteristics of active optical systems based on metal vapors, as well as in visual-optical diagnostics in laser monitor circuits on their basis.

This paper considers the problem of classifying cloud images, which are complex texture structures with heterogeneous characteristics. Traditional image analysis methods do not always adequately classify such images, and modern deep learning methods require large amount of data and computational resources. The research focuses on evaluating the feasibility of developing a hybrid method combining traditional statistical approaches to texture description and state-of-the-art deep learning techniques. It was hypothesised that the high-level features extracted by a neural network during training can be insufficiently sensitive to subtle local differences in cloud formations. The hybrid approach was implemented and analysed; low-level texture features were extracted from the images before being analysed by the neural network. However, the test results showed that this technique did not improve the classification quality and turned out to be less effective in terms of accuracy compared to the use of unprocessed images. The results of this work can be of interest to specialists in of Earth remote sensing data analysis, meteorology, and development of new texture image analysis methods.

Experimental data obtained in the surface air layer at two observation sites with the underlying surface different in structure are used to estimate the Monin-Obukhov (MO) scale for different types of temperature stratification. The MO scale (its sign, first of all) is compared with the current temperature profile in the surface air layer. It is shown that the sign of the MO scale not always corresponds to the actual temperature stratification.

Carbon dioxide (CO₂) is one of the main greenhouse gases; the study of its effect on the atmosphere on global and regional scales is of current importance. The development of technical means for remote gas analysis of the atmosphere is associated with the development of new and modernization of existing lidar sensing technologies. The paper presents the results of the development of a 2-μm pulsed differential absorption lidar system for sensing CO₂ along horizontal paths in the atmosphere. The configuration and design of the lidar components are shown. Technical characteristics of the lidar system are provided. The results of lidar measurements of the time variation in CO₂ concentration within the city of Tomsk in winter along a selected sensing path using a topographic target (forest belt) are presented. CO₂ concentrations in the range of 435.2-445.1 ppm, corresponding to the background state of the atmosphere, were retrieved from recorded lidar signals. To confirm the correctness of the lidar data, the CO₂ concentration was synchronously measured using a mobile gas analyzer. Analysis of the results shows that the error of lidar measurements of the CO₂ concentration is 1.3%. The results of the work can be useful in the design, manufacture, and modernization of pulsed IR lidar systems for remote sensing of CO₂ and other atmospheric gases.