Atmospheric and Oceanic Optics最新文献

The dependence of the concentrations of cultivated microorganisms and total protein on meteorological parameters (wind direction and speed, solar radiation, temperature, atmospheric pressure, relative and absolute humidity) is studied based on three years measurements. Sampling was carried out at the site of the State Scientific Center of Virology and Biotechnology “Vector” of Rospotrebnadzor, Koltsovo, Novosibirsk region, with simultaneous recording of weather conditions. The concentration of total protein was determined by the fluorescence method of a protein binding reagent, and the concentration of cultivated microorganisms was determined by standard cultural methods. Weather parameters were received from a weather station located near the sampling site. The analysis of the data shows that the concentrations of biological components in aerosol increase with the average temperature, absolute humidity, and illumination during sampling and decrease with an increase in the average relative humidity, wind speed, and atmospheric pressure.

Dust aerosol from the regions of sandstorms is transported by air masses to thousands of kilometers, affecting the optical properties of the atmosphere, climate, and terrestrial natural objects. The northern Caspian region (Kalmykia, the Volga Delta, the Transcaspian lowlands, and northwestern Kazakhstan) is a year-round source of dust aerosol. Based on the data of Mosecomonitoring stations for 2011–2021 we analyzed the episodes of an increase in the level of aerosol pollution in Moscow near-surface air associated with long-range atmospheric transport of dust from the Caspian region. Eight months (about 6%) with the daily PM₁₀ concentration in Moscow higher than MPC value during 3 or more days were revealed. The duration of each episode ranged from 3 to 10 days, and as a total they did not exceed 9% of days per year on average. During those episodes the maximal daily PM₁₀ concentration in the near-surface Moscow air was 2.7 ± 1.1 times higher than the corresponding monthly values. The months with episodes of long-range atmospheric dust transport to Moscow are characterized by 1.9 ± 2.0°C higher air temperature and by 9 ± 13 mm lower precipitation amount relative to the corresponding norms for Moscow.

The effect of two factors, i.e., the dependence of the broadening coefficients γ and shifting coefficient δ on the speed ({{{v}}_{a}}) of absorbing water vapor molecule (wind effect) and a change in the H₂O molecule speed upon collision with gas atoms, on the profile of an absorption line of water vapor in a mixture with helium, argon, krypton, and xenon is studied with three absorption lines of H₂O molecule from ν₁ + ν₂ + ν₃ band with different rotational quantum numbers of the initial quantum state. The wind effect is shown to be the strongest in interactions of H₂O molecules with argon, krypton, and xenon atoms. The results can be used in the analysis of absorption spectra of water vapor mixed with monatomic gases.

The effect of impurity Mg and Ca atoms on the optical breakdown threshold of a nonlinear ZnGeP₂ crystal at a wavelength of 2.097 μm is studied. An impurity was introduced through diffusion doping by sputtering on a ZnGeP₂ substrate followed by annealing in vacuum at a temperature of 750°C for 200 hours. Mg atoms introduced into a single crystal increase the optical breakdown threshold by 31%. When ZnGeP₂ is doped with Ca atoms, the opposite trend is observed. The changes in the optical breakdown threshold are suggested to occur due to the creation of additional channels for energy dissipation of radiative and fast nonradiative relaxation processes through impurity energy levels. This suggestion requires experimental confirmation. An increase in the optical strength of ZnGeP₂ could expand the scope of its applicability.

An expert assessment of the accuracy codes for the intensities of rovibrational transitions of water vapor in the spectral range 2500–6500 cm^–1 of the HITRAN2020 database has been carried out. From comparison with experimental data, the normalization coefficients of the variational calculation by Conway E.K., Gordon I.E., Kyuberis A.A., Polyansky O.L., Tennyson J., Zobov N.F. // J. Quant. Spectrosc. Radiat. Transfer. 2020. V. 241. P. 106711 were determined; for the absorption bands (001)–(000), (020)–(000), (011)–(000), and (110)–(000), they were 1.010, 1.007, 1.013, and 1.030, respectively. Using variational calculations and modeling based on the effective Hamiltonian approach, the analysis of experimental data from the HITRAN2020 database has been carried out, revealing less accurate values. Based on these results, an adjusted list of H₂¹⁶O absorption lines in the range 2500–6500 cm^–1 has been constructed, which can be useful for natural experiments.

Estimating the influence of atmospheric turbulence on the quality of astronomical images requires appropriate investigations at the sites of observatories. The results of long-term measurements of the atmospheric turbulence characteristics in the Sayan Solar Observatory (SSO) of the Institute of Solar-Terrestrial Physics, Siberian Branch, Russian Academy of Sciences, in summer 2023 are presented. It is confirmed that the cause of the prevailing direction of local winds appearing in SSO is the temperature mountain-valley gradient between the Sayan Mountains north of the SSO observatory and the valley to the south. A smaller level of the mean intensity of atmospheric turbulence in the SSO compared to the turbulence over a flat terrain in middle latitudes is confirmed. The presence of coherent turbulence in the SSO area is shown, at which the quality of images obtained by optical instruments is improved. New data are obtained for the turbulent scales of temperature and wind speed used in the Monin–Obukhov similarity theory depending on the atmospheric stratification. The results will be useful for specialists in astroclimate and theory of atmospheric turbulence.

Clear air turbulence (CAT) constitutes the highest danger for aviation in the free atmosphere in the altitude range 6–12 km. Intermittence and random localization of CAT in a quiet surrounding air flow significantly restrict possibilities of its forecasting. Creation of systems for remote detection of turbulent zones becomes especially topical with allowance for climate changes and increase in the probability of CAT appearance. Results of turbulence sounding by the BSE-5 UV lidar from the Optik Tu-134 aircraft laboratory are presented. The in-flight experiment was conducted in September 2022 as part of the Arctic exploration program. The lidar recorded zones of moderate turbulence in the lower troposphere where the probability of turbulence is maximum; isolated cases of CAT were also recorded at an altitude of 9 km. The turbulent lidar can be used in practice for remote detection of turbulent zones at altitudes where most commercial flights are carried out. The prospects of ground-based application of the turbulent lidar for solving aviation safety problems during flights in the lower troposphere are also shown. The results of the BSE-5 lidar sounding in winter, when an increase in the intensity of turbulence in the 0.4–1.6-km layer was recorded during the passage of a cold front, are presented.

The processes of planetary wave breaking (Rossby Wave Breaking – RWB) significantly contribute to variability in stratospheric circulation. Employing a previously developed method for identifying RWB, adapted for stratospheric circulation, this study analyzes the climatology and long-term variability of RWB processes in the middle stratosphere. The method is based on the analysis of potential vorticity (PV) contour geometry at the 850-K level using ERA5 data within the PV range 0–400 PVU (Potential Vorticity Units) determined based on PV field climatology. It was demonstrated that RWB processes exhibit intraseasonal peculiarities. Most frequently, waves break in the northern regions of East Asia and the Pacific Ocean from October to December and in April to March. In January and February, no areas with prevailing RWB processes were identified. We obtained a statistically significant increase in the number of RWB for the first half of winter (October–December) and for the end of the winter period (March and April). For midwinter (January and February), insignificant negative trends were obtained. The results of this work can be used to analyze the long-term variations in stratospheric circulation and, in particular, the occurrence of stratospheric anomalies preceding sudden stratospheric warmings.

Laser radiation in the yellow wavelength range is widely used in ophthalmology due to its effectiveness and unique properties. Commercial medical laser systems existing today have low pulse power and other disadvantages. A yellow neon laser with a wavelength of 585.3 nm can be suggested as alternative. We experimentally study a neon laser pumped by a pulsed inductive longitudinal discharge; a Ne–H₂ gas mixture with various ratios is used as the active medium. The shape and duration of the lasing pulses strongly depend on the ratio Ne : H₂, providing both single and double pulses with a total duration of 30 to 100 ns (FWHM). The generation energy attains 20 μJ, which corresponds to a pulse power of 200 W. The laser beam cross section is close to a circle in shape; the beam divergence is lower than 2 mrad. In future, an inductive neon laser operating in a pulse-periodic mode with a pulse repetition rate of up to 100 Hz can be used for various applications, including in medicine.

IR lasers are widely used in various fields of science and technology. In this regard, expanding the spectral range and obtaining effective lasing in the IR is an urgent task. The object of our study is an self-terminating Eu laser radiating at a wavelength of 1.76 μm. We study a possibility of increasing the output parameters of this laser by elongating the active zone of a gas discharge tube (GDT). An increase in the GDT volume from 157 to 314 cm³ at a constant pumping power of 1200 W makes it possible to double the output power and laser efficiency. An average radiation power of 2.5 W was attained for the first time in 1.76 μm line; a maximal efficiency of 0.3% was attained at a pump power of 500 W. After 100 hours of operation, the energy characteristics of the Eu + Ne laser with the active zone of 314 cm³ in volume show good repeatability, which allows us to conclude a possibility of further increasing the energy characteristics and lifetime of this laser. Our results can be useful in microprocessing of materials and in active optical systems for visualizing fast processes.