Atmospheric and Oceanic Optics最新文献

The main source of summer heating of the upper layer of Siberian Arctic shelf seas is shortwave solar radiation. The radiation flux attenuates as it passes through the water depth, and the attenuation rate is determined by the optical properties of water, which mainly depend on the concentration of suspended matter in the water. In numerical models of the ocean and sea ice, the process of shortwave solar radiation absorption is described by different parameterizations. In this work, the sensitivity of the numerical 3D regional ocean and sea ice model SibCIOM to two parameterizations of the penetrating radiation is studied: (1) two-component parameterization with constant attenuation coefficients for the infrared and visible spectral regions depending on one of ten ocean water transparency classes; (2) three-component parameterization with different absorption coefficients for the red, green, and blue parts of the visible spectrum, which is based on satellite data on chlorophyll concentration. The analysis of the results of numerical experiments for the water area of Siberian shelf seas has shown that if the seasonal distribution of chlorophyll concentration is taken into account when simulating a penetrating shortwave radiation flux with the RGB parameterization, then regions of water warming are formed in the surface or bottom layer, which differ from a basic experiment with the two-component parameterization. The comparison between the simulation results with observations shows the RGB parameterization to be preferable for the numerical simulation of Arctic shelf seas.

Abstract—To determinate the atmospheric turbulence type (Kolmogorov, coherent, etc.) in operational mode, a new technique has been developed based on an algorithm for spectral analysis of sequential overlapping samples from a continuously replenished population of meteorological measurements. The samples are generated by the sliding time window method. A turbulence type criterion is the slope of the inertial interval of the spectrum of temperature fluctuations 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 specified by the decrease by one order of magnitude from the maximum. It is shown that these slopes are lognormally distributed for the recorded meteosituations under urban conditions. 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 data on the wind speed and recording time. It is shown that the extent of the regions can significantly exceed the length of a region for an ordinary sample under comparable conditions. 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 suggested technique in astronomical practice is the estimation and registration of the sizes of spatial regions of strong and weak turbulence, where the turbulence intensity is within fixed ranges, along an optical path, as well as the sizes of regions with fixed temperature stratification.

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.