Home – Home – Jornals – Atmospheric and Oceanic Optics 2022 number 9

The results of numerical simulation based on the Mie theory of the superresonance effect in a dielectric sphere with a low refractive index are presented. Water was used as the material of the mesoscale sphere. It is shown that not only the previously studied weakly dissipative mesoscale spheres made of a material with “medium” (~ 1.5) and high (> 2) refractive indices, but also with a low one (~ 1.3) support the high-order Fano resonance effect associated with internal Mie modes. In this case, the intensities of resonant peaks for both magnetic and electric fields can attain extremely high values on the order of 10⁶-10⁷ in the vicinity of the poles of a water droplet with a Mie size parameter of ~ 70.

The paper presents the results of complex experimental studies of gas impurities and the vertical structure of aerosol in the atmosphere over Lake Baikal in September 2021, using the research vessel (RV) "Academician V.A. Koptyug". Measurements of gaseous impurities in the near-air layer were carried out using local control means - chemiluminescent gas analyzers. The sounding of aerosol fields was carried out using a multi-frequency polarization aerosol-Raman lidar "LOSA-A2". Compared to previous expeditions, in 2021, low concentrations of gaseous impurities and aerosols, close to the background ones, were recorded. The analysis showed that the main contribution to atmospheric pollution was made by nearby local sources located near the coastal zone of the lake.

The approbation results for the algorithm of detecting specularly reflecting layers in high-level clouds based on passive satellite data are presented. We consider cirrus clouds with an optical thickness of less than 5 and a top height of more than 8300 m consisting of horizontally oriented ice crystals, observed over the territory of Western Siberia from 2006 to 2007. The technique for detecting specularly reflecting layers in high-level clouds is described and the statistical analysis of their parameters is performed on the basis of spectroradiometer MODIS satellite data. We discuss the seasonal and latitudinal properties of the parameters of considered clouds over Western Siberia..The typical values of the area, top height, reflection ratio, and effective emissivity of specularly reflecting layers over different latitudinal zones of the target region were estimated for the first time.

In this work, the long-term series of vertical stratification of aerosol in the stratosphere are processed and analyzed with the use of the scattering ratio as an example, as well as the vertical distribution of aerosol scattering coefficients at a wavelength of 532 (altitude range 15-50 km) over Tomsk. The experimental data were received from regular measurements at the lidar station of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, in 2010-2021. On the basis of the accumulated experimental material, regional features of the intra- and interannual variability of the stratospheric aerosol in Western Siberia were revealed. An optical-aerosol model of the atmosphere is suggested for this region, more adequate to actual conditions are compared to existing ones.

Possibilities of wind speed measurement in the atmospheric layer from 10 to 20 km with a ground-based pulsed coherent Doppler lidar (PCDL) operating on molecular light scattering are numerically studied. Requirements for the parameters of PCDL with sounding radiation wavelengths of 1 and 2 mm for receiving reliable information about the wind speed and direction in the atmospheric layer under study are determined in numerical experiments.

The reasons are found for a decrease in the sensitivity of a TROA (time-resolved optoacoustic) detector in spectrometers with pulsed lasers and of a non-resonant OA detector in spectrometers with cw lasers when buffer gas nitrogen (air) is replaced by hydrogen in mixtures with an absorbing gas. In the first case, the reason is the high speed of sound in hydrogen at an insufficiently wide working frequency band of the microphone. In the second case, the reason for the loss of sensitivity is the low dynamic viscosity of hydrogen, which results in faster pressure equalization in the pre- and behind-membrane volumes of the OA detector chamber for a light pause as compared to heavier molecular gases. Therefore, the amplitude of an OA signal at the modulation frequency of the cw laser radiation increases in proportion to the dynamic viscosity of the gas.

The mixed moments of wind vector components on the turbulent and meso-gamma scales calculated from experimental data obtained in the surface air layer at an altitude of 10 m are compared. The statistics of mixed moments for several months in different seasons of 2021 is presented. The dependence of mixed moments on the wind velocity and temperature stratification in the surface air layer is briefly analyzed. The values of mixed moments formed by the wind field components on the meso-gamma scale are comparable with those formed by the mixed moments of turbulent components of the wind vector.

The simulation results the radiative forcing of smoke aerosol (RFA) at the boundaries of the atmosphere are considered depending on the photochemical evolution of its organic component, illumination conditions, and underlying surface types (water, mixed forest, and snow/ice). An increase in the albedo of the underlying surface and a decrease in the aerosol optical depth can lead to the transformation of the cooling effect into heating at the top of the atmosphere. An increase in the absorbency of aerosol particles is the cause of an increase in RFA at the top of the atmosphere, which is most significant over snow/ice surfaces, while at the bottom of the atmosphere, RFA decreases. As the solar zenith angle increases, the absolute value of RFA decreases as the smoke plume propagates over weakly reflecting surfaces, but with an increase in the albedo of the underlying surface, this dependence transforms into a nonmonotonic one. It is shown that neglecting the transformations of the optical characteristics of organic aerosol can lead to overestimation or underestimation of the radiative forcing of the aerosol at the top of the atmosphere by several times (by several tens of W/m²), and also cause an error in determining the RFA sign.

Here we discuss methodological aspects and approaches to solar radiation measurements at the Fonovaya Observatory of IAO SB RAS, as well as capabilities of the new radiation unit mounted there in 2020. It is equipped with a set of instruments which allow continuous monitoring of the total (0.285-2.8 mm), total UV (0.280-0.400 mm), and UV-B radiation (0.280-0.315 mm) and the energy balance between incoming short-wave and long-wave far infrared radiation. The capabilities of measurement data collecting, transmitting, and processing of the specially developed software are described.

The design characteristics of the turbulent lidar affecting its thermo-mechanical stability are determined. A comparative description of two different designs is given, where different approaches are implemented to the selection of transceiving optics and receiver detectors and organization of the temperature control system for stabilizing the lidar optical bench. A simulation scheme of a lidar transceiver is suggested, including the calculation of the displacements of optical elements relative to the base points on the optical bench and the ray tracing from the laser into the atmosphere and back. The influence of the temperature gradient between the opposite sides of the optical bench on the operation of the receiving channels is considered. The results of the experimental study of lidars for resistance to temperature changes are presented. Recommendations for improving the design of a turbulent lidar are formulated.

The conditions for generation of red streamers at an atmospheric air pressure of 0.1-10 Torr are experimentally studied. The mode of generation of streamers tens of centimeters in length from the plasma of an electrodeless capacitive discharge is implemented under low pressures. A discharge between metal small-curvature electrodes transforms into a stationary mode, where streamers are not generated, as the pressure and voltage increase. It was confirmed using the ICCD camera that the streamers start from the positive-polarity electrode. The color of the discharge plasma depends on the air pressure in pulsed and continuous discharges and is most consistent with the color of red sprites at a pressure of ~ 1 Torr.

The CO₂ content in tree wood and the radial increment of trees can change under the impact of ground fires. The larch discs under study survived the fire of 1908 after the explosion of the space body in the Podkamennaya Tunguska revealed a number of features in the behavior of absorbed CO₂ and (CO₂ + H₂O) in larch wood. The photoacoustic analysis of samples vacuum-desorbed from tree rings has shown a long-term annual accumulation of CO₂ and (CO₂ + H₂O) in tree stems after 1908. A change in CO₂ release cycling in the post-catastrophic period is ascertained. A change in variation cycling is also noted in the tree ring chronologies. According to the analysis of the correlation coefficients, the specific behavior of the larch ring width chronologies in this region is most likely due to variations in the solar activity.