Home – Home – Jornals – Atmospheric and Oceanic Optics 2024 number 7

The absorption spectrum of the ¹⁴N¹⁷O molecule in the range 5200-5550 cm^-1 was recorded for the first time using a Bruker IFS-125M Fourier spectrometer with a spectral resolution of 0.0056 cm^-1. An analysis of the spectrum made it possible to detect 83 vibrational-rotational lines of the 3-0 band of the main transitions in the X ²P electronic state of the ¹⁴N¹⁷O molecule. For 29 resolved doublets, the positions and relative intensities of each component of a doublet are determined. The spectroscopic Λ-parameters are found. For the remaining 25 unresolved doublets, the positions and relative intensities of the doublet center are also determined. The maximum of the rotational quantum number J was 24.5. The found experimental line positions in the 3-0 band confirmed the calculated data given in the ExoMol database. The frequencies of registered transitions weighted in accordance with experimental uncertainties have been processed, and the spectroscopic constants for the vibrational state v = 3 have been determined. With the found spectroscopic constants, predictive calculations were made of the rotational energy term values up to J = 30.5 in the vibrational state v = 3 and, accordingly, the transition frequencies of the 3-0 vibrational band for ²Π_1/2 and ²Π_3/2 electronic states. The calculations performed showed agreement with the data given in the ExoMol database, within the error specified.

Accurate measurements of the concentration of nitrous oxide, a potent greenhouse gas, in the Earth's atmosphere are important for modeling the radiation balance of our planet. The work presents the measured broadening and shift coefficients of N₂O lines by air pressure at room temperature for 82 rovibrational transitions in the (00⁰2) ← (00⁰0) band; the rotational quantum number m varies from 3 to 54. The measurements were carried out on an IFS-125M Fourier transform spectrometer with a spectral resolution of 0.0056 cm^-1. The calculated line-broadening and shift coefficients were obtained using a semi-classical method modified by introducing a correction factor in the calculation scheme. Our parameters are compared with those presented in the literature and in modern spectroscopic databases. A vibrational dependence of the line half-widths for the ν₃ stretching vibration was revealed.

For five isotopologues of the SO₂ molecule: ³²S¹⁶O₂, ³⁴S¹⁶O₂,³³S¹⁶O₂, ³²S¹⁸O₂, ³²S¹⁶O¹⁸O, parameters of the effective vibrational Hamiltonian are derived from fitting to the available experimental data and with the use of the basic relations of the isotope substitution theory. Vibrational constants obtained from the fit reproduce the experimental vibrational energy levels within 0.025 cm^-1 for symmetric isotopologues. The found vibrational energy levels are compared with the variational calculation data, and the quantum numbers for 93 vibrational states are corrected.

To determinate the type of atmospheric turbulence (Kolmogorov, coherent, etc.) in operational mode, a new technique has been developed based on algorithm for spectral analysis of sequential overlapping samples from a continuously replenished population of meteorological measurement data. The samples are formed by the sliding time window. Criterion for turbulence type is the slope of inertial interval of the temperature fluctuation spectrum near the maximum, which is equal to “-5/3" under Kolmogorov turbulence and “-8/3" under coherent turbulence. The slope is calculated from the linear regression equation at the initial part of the spectrum, the length of which is set by the level of decrease by one order of magnitude from the maximum. It is shown that such slopes of the spectra for the recorded meteosituations under urban conditions are distributed lognormally. It is found that the proportion of non-Kolmogorov turbulence in more than 5 million calculated spectra is much larger than expected and amounts to 75-97% depending on the estimation rigor. It is shown that sequences of spectra with the same slope correspond to regions of turbulence of the same type. Boundaries of the regions are defined with accuracy of the sliding window shift step. The size of the regions is estimated based on information about wind speed and registration duration. It is shown that under comparable conditions the extent of the regions can significantly exceed the one for an ordinary single sample. To accelerate the post processing of large datasets, the algorithm uses the Message Passing Interface (MPI) for a computing cluster with an arbitrary number of nodes. The field of application of the technique in astronomical practice is the evaluation and registration of the sizes of spatial regions of “strong" and “weak" turbulence along optical path, in which the intensity of turbulence is in fixed intervals, as well as the sizes of regions with fixed temperature stratification.

The purpose of the study is to describe the seasonal variability of optically active components in the Sea of Azov based on continuous information obtained from the combined MODIS-Aqua/Terra satellite observation product and a three-dimensional hydrodynamic model. The paper discusses the results of testing a method for restoring missing data in remote sensing images using the results of three-dimensional hydrodynamic simulation. The method has been tested for four main bio-optical parameters: the concentration of chlorophyll- a and pheopigments (TChl), indicators of light absorption by phytoplankton pigments ( a _ph(678)) and non-living organic matter ( a _CDM (438)), and indicator of backscattering of light ( b _bp(438)). The results obtained from the combined product were compared with in situ observations carried out in April-May 2019 on the SRV Professor Vodyanitsky. The deviation of the average TChl values according to MODIS and simulation data relative to in situ observations was 1.8 and 2.2 mg × m^-3, respectively. Analysis of the calculated series of main bio-optical parameters obtained through regular assimilation of MODIS data into a hydrodynamic model made it possible to establish their seasonal variability for the central part of the Azov Sea in 2019. Among the studied bio-optical parameters, a clear seasonal variability of TChl stands out with an average annual value of 2.98 ± 1.22 mg × m^-3. Changes in a _CDM(438) and b _bp(438) are characterized by two periods of greatest values: spring (March-May) and autumn (August-October), with corresponding annual averages of 0.42 ± 0.15 and 0.10 ± 0.03 m^-1. Maximal changes in a _ph(678) are observed from July to October with an annual average of 0.04 ± 0.03 m^-1. The proposed method takes advantage of remote sensing data, which expand the capabilities of operational oceanological monitoring, and simulation data, which allow filling information gaps in these data. The results provide complete continuous data sets on the distribution of basic bio-optical indicators, which are crucial in predicting the ecological state of sea basins.

Comparison of results of satellite measurements by results of independent measurements is an esencial and necessary component of validation of satellite data, justifying their use for scientific and practical tasks. The work compares the results of spectrometric measurements of the NO₂ content in the atmosphere by the Ozone Monitoring Instrument (OMI) in 2004-2020 with the results of ground-based twilight zenith measurements at 14 stations of the Network for the Detection of Atmospheric Composition Change (NDACC). Latitudinal distributions of quantitative characteristics of the comparison have been obtained, including the NO₂ contents, their differences, and correlation and linear regression coefficients between the satellite and ground-based data. Criteria for validation of interannual and long-term changes in NO₂ derived from the OMI data with the help of ground-based measurements are proposed. The latitudinal - hemispheric and regional - features of the correspondence between the satellite and ground-based data have been revealed. Significantly new results have been obtained on the dependence of the comparison characteristics on the level of pollution of the lower troposphere with nitrogen oxides and on the time scale of NO₂ variations: day-to-day, seasonal and interannual. The results will be useful in analysis of NO₂ variability based on OMI data. The continuation of this work may be a comparison of the results of the analysis of interannual variations and long-term NO₂ trends obtained on the basis of the OMI and ground-based measurement data.

This work is devoted to the issues of remote monitoring of atmospheric gas concentrations using the example of carbon monoxide over the oil and gas producing territories of the Khanty-Mansi Autonomous Okrug with a high concentration of fuel combustion sources. The analysis of the variability of carbon monoxide (CO) content in the atmosphere over an oil-polluted area in the Khanty-Mansi Autonomous Okrug is performed based on satellite sensing data (Terra/MOPITT). The daily and seasonal dynamics of the integral content and surface concentration of CO are studied. The average CO content (integral and surface) in the oil-polluted area exceeds similar values in the background area, both in general for the warm period of the year and for most months. There are no significant differences in the CO content above the background and contaminated areas, which may be due to the mixing of air masses; however, the average CO content (integral and ground level) in the contaminated area exceeds similar values in the background area, which is explained by the presence of stationary CO sources in the former, including flare units.

According to the IPCC-2021 Report on climate change, the atmospheric CO₂ and CH₄ concentrations have increased by around a quarter for the last 50 years. The CO₂ and CH₄ radiative forcing due to their concentration growth was calculated for mid-latitudes. The vertical profiles of temperature and humidity were taken from the ECMWF ERA-5 European reanalysis data. An impact of overlapping of H₂O absorption bands with CO₂ and CH₄ bands on the radiative forcing calculation results in the troposphere and stratosphere of mid-latitudes with different water vapor content was investigated by statistical methods. It was shown that absolute value of the CO₂ radiative forcing in the troposphere increases with the atmospheric water vapor content, whereas the CH₄ radiative forcing does not depend on the atmospheric total column water vapor.

This paper presents the results of an experiment on remote sensing of a smoke plume over a model fire with the use of a specialized lidar based on the backscatter enhancement effect and detecting optical turbulence. Burning was 1.600 m away, and the area of the model fire varied from 1, 9 and 25 m². It was found that during combustion, the lidar recorded an increase in the echo signal in the main receiving channel, which registers aerosol scattering and the turbulent component, relative to an echo signal in the additional receiving channel, which registers only the aerosol. The width of the smoke plume did not exceed 20 m, an increase in the main echo signal was observed immediately after the plume in the distance range up to 300 m. In this experiment, a plume of warm smoke acted as a phase screen that changed the coherent structure of the laser beam. After the completion of intensive combustion, the temperature inside the plume rapidly decreased and the lidar recorded only the aerosol content. The appearance of two signs in the echo signal - an increase in the aerosol concentration and turbulence intensity - clearly indicates a source of burning. The lidar estimation of the values of the structural characteristic of the refractive index C_n² at an altitude of 10 m above the combustion focus was compared with the data of the ultrasonic meteorological station AMK-03 at an altitude of 3 m and results of simulation of a grass-roots fire published earlier.

The laser fragmentation/laser-induced fluorescence (LF/LIF) method is well known for its efficiency in detecting complex chemical compounds based on the fluorescence of their characteristic fragments. The method is applied, for example, to measuring the local content of nitrous acid and hydroxyl radicals in the atmosphere, visualization of intermediate stages of combustion processes, remote detection of substances in the gaseous state in the atmosphere and condensed state on surfaces, etc. We present for the first time the results of the experimental study of a possibility of remote excitation of LIF of characteristic photofragments of a substance in an aerosol state in the atmosphere. The organophosphorus compound triethyl phosphate (TEP) was used as the test substance. It has been shown that synchronized two-pulse laser irradiation of TEP aerosol particles and their PO-fragments (phosphorus oxide molecules) makes it possible to increase the efficiency of the LF/LIF process by approximately seven times compared to single-pulse laser exposure. It has been established that the process of formation of PO-fragments of TEP aerosol under the laser irradiation at a wavelength of 266 nm has a decaying exponential character with a characteristic time of 192.6 ± 20.2 ns. In terms of the nature of the time dependence of the formation of photofragments, the results obtained are fundamentally different from similar measurements for other compounds in gaseous and condensed states and motivate further research that will contribute to the development of the LF/LIF method.

To monitor objects of man-made origin, the issues of reducing the errors of pointing an optoelectronic system (OES) of a space survey at an object, which are associated with the influence of mechanical factors on the design of a pivoting device, are considered. To reduce these errors, the calibration of the optical sensors of the OES by stars is used. Mathematical methods of processing measurements are used to increase their accuracy, or interpolation methods are used to determine intermediate values between measured calibration points. The work uses spline approximation to find corrections to the readings of optical sensors of the azimuthal and elevation axes.

Erebus volcano is the southernmost active volcano on Earth, whose volcanogenic emissions include components that play a significant role in catalytic cycles of stratospheric ozone depletion. High cyclones contribute to the rise of gas emissions from Erebus volcano (including HCl and SO₂) from the troposphere to the altitudinal range of ozone hole formation, from 14 to 22 km in the stratosphere. The paper considers the integral content of HCl and ClONO₂ for the period 1992-2023 and analyzes the variability of the frequency of high cyclone occurrence for the period 1980-2022 based on the ERA5 reanalysis data. It is revealed that the maximal frequency of occurrence of high cyclones over Erebus volcano is usually observed in July. The analysis of the integrated HCl content at different stations showed that the values over the Antarctic are much higher than over the Arctic and approximately twice as high as at midlatitude stations. The effect of HCl accumulation in the stratosphere is shown: the correlation coefficient between 5-year average frequencies of occurrence of high cyclones and 5-year average values of ozone hole area with a 4-year shift of the series of the ozone hole area ahead relative to the series of the frequency of occurrence of high cyclones, calculated for the period from 1980 to 2022, amounts 0.78.