Atmospheric and Oceanic Optics最新文献

A compact absorption spectrometer with a narrowband continuous tunable diode laser is created; it provides sensitivity on the order of 1 × 10⁻⁶ cm⁻¹ in terms of the absorption coefficient. The design of the spectrometer, the measurement technique, and the ozone generation and control procedure are described. The absorption spectrum of the ozone molecule is recorded for a system of Wulf bands in the near-IR range 11 900–12 800 cm⁻¹, which correspond to rovibronic transitions from the ground to excited triplet electronic states above the main dissociation threshold of the molecule. The absorption coefficient is simulated and predissociation broadening of spectral lines is estimated in the spectral range under study based on the simulation results. Ozone absorption cross sections in this range are recommended for atmospheric applications; they have been derived using statistically weighted averaging of the new measurements and published laboratory experimental data.

High-resolution spectra corresponding to the rotational and the ν₂–ν₂ bands of the two most abundant isotopic species of ozone with one heavy ¹⁸O oxygen atom were recorded using SOLEIL synchrotron radiation source in the range 30–200 cm⁻¹. Additionally, the ν₂ vibrational-rotational bands were recorded between 550 and 880 cm⁻¹ using a classical glowbar source that made it possible to extend and refine information compared to published data on the observed transitions of these bands. The analyses of recorded spectra permitted us to deduce experimental set of energy levels for the ground (000) and the first bending (010) vibrational states, which significantly exceeds literature data in terms of rotational quantum numbers. For both isotopic species, the weighted fits of all experimental line positions were carried out including previously published microwave data. As a result of this work, the improved values of rotational and centrifugal distortion parameters for the states (000) and (010) were obtained that permitted modelling the experimental line positions with a weighted standard deviation of 1.284 (2235 transitions) and 0.908 (4597 transitions), respectively, for ¹⁶O¹⁶O¹⁸O, and 1.168 (824 transitions) and 1.724 (2381 transitions) for ¹⁶O¹⁸O¹⁶O.

Based on long-term study in the Kara Sea basin (11 expeditions in 2007–2022), we, for the first time, statistically generalize atmospheric aerosol characteristics: the volume concentrations of submicron and coarse aerosol (V_f and V_с), the black carbon concentrations (еВС), and the spectral aerosol optical depth (AOD) of the atmosphere. High concentrations of submicron and absorbing (eBC) aerosol are pronounced in the average spatial distribution in the southwestern part of the Kara Sea, and they are minimal in the northern part. The difference in the average V_f and еВС between these regions is 30–60%. The average aerosol characteristics for the entire Kara Sea are: the atmospheric AOD (0.5 μm) is 0.043 with an Ångström exponent of 0.8, еВС = 22.8 ng/m³, V_f = 0.26 μm³/cm³, and V_с = 1.39 μm³/cm³. The average V_f and еВС over the Kara Sea are shown to be intermediate between the values for the Cape Baranov and the Barents Sea.

Atmospheric waves are of increased interest in connection with exchange processes occurring in the atmospheric boundary layer. Experimental results of sounding mesoscale Kelvin–Helmholtz waves by turbulent lidars in a stably stratified boundary layer of the atmosphere are presented. This paper presents the data of measurements by the BSE-4 lidar (532 nm), which has been working over forest-steppe for a long time. Atmospheric waves in most cases were observed in the evening and at night in the range of heights from the land to 600 m, when the Richardson number in the surface air layer did not exceed a critical value of +1/4. Fourier analysis of the time series of the structural characteristic of the refractive index (C_{n}^{2}) shows that the spectrum of the wave process in the atmospheric boundary layer consists of a set of monochromatic waves with different oscillation frequencies. During the observations, the period of the waves varied from 1 to 11 min, and their amplitude changed from 20 to 300 m. It is found that monochromatic waves exist from half an hour to two hours. The disappearance of some monochromatic waves is compensated by the appearance of new ones. The process of generating small-scale turbulence runs throughout the life cycle of a Kelvin–Helmholtz wave. The experimental results indicate that the turbulent lidar is a sensitive device ensuring remote detection and observation of atmospheric waves.

An original technique is suggested for pumping a pulsed CO₂ laser by a longitudinal discharge in an alternating magnetic field. A small CO₂ laser with active medium ∼200 mm long, pulse energy of ∼30 mJ, and efficiency of 3.4% is designed on the basis of this technique. It is revealed that the main factor which limits the generation energy of small lasers is the development of current instabilities in a longitudinal discharge over a cross section of the discharge tube. It is noted that the growth of the instabilities accelerates as the pressure of a CO₂ : N₂ : H₂ : He gas mixture increases to more than 0.1 atm and the specific pump power becomes higher than 3 MW/cm³. The use of an external alternating magnetic field superimposed on a pulsed longitudinal discharge makes it possible to increase the total pressure of the gas mixture in the laser to 0.4 atm when maintaining the combustion of the volume discharge.

The ozone behavior in the Arctic is a major recent concern. The ozone anomalies recur every five years on average. The last, record strong decrease of the ozone level in the stratosphere of the Arctic was recorded in March–April 2020. In February 2022, ozone destruction developed according to a scenario very similar to the anomaly of 2020. Like in 2020, in 2022 the ClO mixing ratio, which can be considered a reliable indicator of ozone destruction, strongly increased after the return of sunlight to the Arctic latitudes, but the subsequent ozone depletion process was halted by a sudden major stratospheric warming on March 20, 2022. In this work, we analyze the ozone destruction in 2020–2022 based on measurements of the total ozone content over 2003–2022 from the TEMIS service, profiles of the air temperature and ozone mixing ratio for 2005–2022 and of ClO mixing ratio for 2020–2022 from Aura MLS observations. The following sites are considered: Eureka, Canada; Ny-Ålesund, Norway; Thule, Greenland; and Resolute, Canada. A relationship is revealed between ozone and chlorine oxide contents. High coefficients of correlation between oscillations of the above parameters at about the same altitudes of their recording, as well as between the total O₃ and ClO contents calculated from their profiles, indicate their close interrelation. Hence, the ClO concentration and total content can be used as indicators of ozone destruction in the Arctic stratosphere.

Numerous fields, such as ophthalmology, optical communication, microscopy, and astronomy frequently utilize sensorless wavefront sensing (SLWS) technologies. SLWS technologies are very helpful in correcting wavefront aberrations without the use of dedicated sensors, Future real-time wavefront sensing technologies and algorithms will surely evolve toward sensorless possibilities. However, there are several challenges associated with aberration correction, including multiple image recording and analysis, noisy and insufficient data, data visualization, and system calibration. This study aims to provide an in-depth analysis of SLWS, including its applications, opportunities, challenges, and state-of-the-art techniques. The various SLWS algorithms are discussed, along with their benefits and drawbacks. The results of SLWS can be beneficial in applications where precise wavefront correction is essential for obtaining clear and detailed observations, such as in astronomical imaging or high-resolution microscopy.

Polar vortices play a significant role in the distribution of stratospheric ozone, the movement of air masses in the polar and subpolar stratosphere, and temperature changes over the polar region. An Antarctic polar vortex forms in autumn and reaches its peak intensity in early spring. In late spring, when this vortex weakens, the influence of the lower subtropical stratosphere on it increases. We consider the effect of temperature changes in the lower subtropical stratosphere on the Antarctic polar vortex strengthening. Using correlation analysis and ARA5 reanalysis data, we show a significant increase in the effect of minor temperature changes in the lower subtropical stratosphere on the dynamics of an Antarctic polar vortex in the second half of November.

In order to study temporal variations in the mixing ratios of greenhouse carbon-containing gases and factors influencing them, local measurements of CO₂, CH₄ (January 2013–January 2020), and CO (January 2013–January 2019) mixing ratios in atmospheric air at the monitoring station of St. Petersburg State University are analyzed taking into account trends and seasonal fluctuations. Linear trends for CO₂, CH₄, and CO, which are 2.42 ppm/year (0.60%), 8.6 ppb/year (0.49%), and −3.8 ppb/year (−2.2%), respectively, are in a good agreement with independent estimates of both global/background changes and changes in urban areas. The analysis of the CO/CO₂ emission ratio confirmed that motor vehicles are the dominant anthropogenic source affecting the composition of atmospheric air near the monitoring station of St. Petersburg State University. The results can be used for validation of atmospheric models and independent estimation of greenhouse gas fluxes.

Simple isotopic relations between the energy levels of ³²S¹⁶O₂, ³³S¹⁶O₂, and ³⁴S¹⁶O₂ isotopologues and of other isotopic variants are applied to calculations of vibrational-rotational energy levels. To estimate the accuracy of these isotopic relations, we calculated line centers in the microwave spectrum of ³⁶S¹⁶O₂ isotopologue and compared them with measured ones. The comparison shows their quite satisfactory agreement at a level of 10⁻⁴ cm⁻¹. Vibrational-rotational energy levels of sulfur dioxide isotopologues ^XS¹⁶O₂, X = 35–38, are presented for five lower vibrational states up to J = 9.