Atmospheric and Oceanic Optics

For the first time, a 15-dimensional analytical form was obtained and the potential energy of the SF₆ molecule in the ground electronic state was found. An optimal grid of geometries was constructed, which, taking into account the full symmetry of the molecule, unambiguously determines the potential energy surface of the sixth order. Using the MP2 method with the cc-pVTZ base set, the potential energy surface of the fourth order was calculated.

A technique is suggested for estimating the spectral resolution of video spectrometers in separate sections of the sensitivity scale via comparison of experimental survey results with model (calculated for the same observation conditions) Fraunhofer lines from a set of preset values. The maximal estimation errors of the technique suggested are within 0.5 nm at the considered test lines 700 and 587 nm for both mass-produced spectroradiometers and original video spectrometers.

A method for the joint determination of microphysical aerosol characteristics, namely, the complex refractive index \(m = m_{\text{real}}^{{}} + im_{\text{image}}^{{}}\) and spherical-particle size distribution function U(r), from the data of nighttime lidar sensing at wavelengths of 355–1064 nm is proposed. During their simultaneous estimations, it is useful to directly minimize the discrepancy functional Φ(m) in the range of the physically justified m. The principal limitations due to a wider region of the global minima of Φ(m) appear at \(m_{{{\text{image}}}}^{{{\text{true}}}} \in \) [0.01, 0.04] and give rise to a potential shift of the resulting values of \(m_{\text{real}}^{\text{est}}\) and \(m_{\text{image}}^{\text{est}}\). A simultaneous use of several functionals gives a better estimate of m due to different sets of the respective optical characteristics. The problem in retrieving the size distribution function is caused by the information content of the coarse particle measurements. The statistical regularization method offers an unambiguous estimation of U(r) for the mean radius up to 3 µm and gives an admissible estimate for larger radii. The algorithms are tested on eight values of absorption, when one value corresponding to one \(m_{\text{image}}^{\text{true}}\) is associated with 50 empirical models of the distribution function.

According to satellite monitoring data (MODIS/Terra), the spatial distribution of the aerosol optical depth (AOD) at a wavelength of 550 nm for the summer smog of 2007 over the North China Plain (NCP) and adjacent areas has been obtained. Areas over which the AOD is higher due to regional anthropogenic contamination sources near Beijing and Shanghai, as well as the smoke haze forming due to agricultural burning (the southwest part of the NCP), have been revealed. The similarity of optical and microphysical characteristics of aerosol in the smoke haze over the NCP and in the Russian territory has been found: (i) the decisive contribution to the optical characteristics of smoke aerosol is made by the fine mode and (ii) the attenuation spectra in the wavelength region 340–1020 nm are approximated (in logarithmic coordinates) by parabolas or fourth degree polynomials. The monitoring data at the AERONET Beijing site show that the single scattering albedo in the summer smog over the NCP is on average less (0.91) than in the smoke haze in the Russian territory (0.95–0.96). The radiative regimes of the atmosphere are significantly different: in the smog, the aerosol radiative forcing efficiency is lower approximately by 30% at the top of the atmosphere and higher by 30% at the bottom of the atmosphere than in the smoke haze.

Based on the integrated monitoring of aerosol characteristics in the suburban region of Tomsk (2000–2017), a version of the classification of states of the surface atmospheric layer with respect to “aerosol weather” types is suggested. The principle of separate study of the processes of variation in the “dry matter” of aerosol particles and their condensation activity is utilized as a basis of the measurement method used. The corresponding aerosol weather types were identified in the coordinates (σ_d; Р), where σ_d is the scattering coefficient of the dry matter of aerosol (λ = 0.51 μm); P is the ratio of the mass concentration of the absorbing substance to the mass concentration of submicron particles, which reflects the “blackening” degree of the particles. With respect to the value of the scattering coefficient σ_d = 100 Mm⁻¹, the dataset is divided into two classes: “atmospheric hazes” (σ_d < 100 Mm⁻¹) and “haze” (σ_d > 100 Mm⁻¹). Then, the observation dataset is divided according to the value P = 0.05. In each calendar season, in accordance with the parameters specified, four types of aerosol weather are identified, which are conventionally designated as background (P < 0.05, σ_d < 100 Mm⁻¹), haze-S (P > 0.05, σ_d < 100 Mm⁻¹), smog (P > 0.05, σ_d > 100 Mm⁻¹), and smoke haze (P < 0.05, σ_d > 100 Mm⁻¹). It is shown that the main aerosol weather types are reliably different in the ratio of the contents of submicron and coarse particles in all seasons.

Changes in ozone concentration during precipitation are studied using data of ozone monitoring in the surface air layer in Tomsk and at Karadag. It is found that these changes can be either positive or negative. The largest jumps in ozone content are observed during frontal precipitations. During air mass precipitation, the sign and magnitude of the changes are determined by the diurnal behavior of ozone concentration. Analysis showed that the increase in the ozone concentration during precipitation and ozone increase in the diurnal behavior are time-coincident in 59% of cases in Tomsk and in 63% of cases at the Karadag. The decreasing wave of ozone concentration in the diurnal behavior coincides in time with ozone decrease during precipitation even more often, in 85% of cases in Tomsk and in 79% of cases at Karadag. Based on data of aircraft sensing, it is shown that ozone descent from the boundary air layer occurs in a number cases when the temperature stratification during precipitation changes to neutral.

An algorithm developed earlier for estimating the circulation of aircraft wake vortices from measurements by a Stream Line pulsed coherent Doppler lidar has been improved by using the model of a pair of aircraft vortices in the algorithm. The model takes into account the ground effect on the spatial dynamics and evolution of the vortices. In a numerical experiment, it has been shown that the improved algorithm allows one to obtain the result with a high accuracy whereas the approach used earlier overestimates the lidar measured vortex circulation approximately by 10%.

A novel metal vapor active element is constructed. The functions of metal vaporization and metal vapor excitation are divided between two different sources, which is a feature of the new element. Metal vapors are formed by induction heating of a dispenser located outside the active zone. The excitation is carried out by the commutation of a high-voltage pump pulse. The efficiency of the design has been tested in the excitation of copper atoms. Under conditions of independent heating of the dispenser, stable lasing was obtained at 510.6 and 578.2 nm lines at a pumping pulse repetition rate of 15 kHz.

Methods for phasing radiation channels for the coherent combination of linearly polarized fields of narrowband fiber lasers are considered. High efficiency of operation of the internal feedback loop based on interference of peripheral sections of radiation (Gaussian beam tails) of the phased channels is shown. This method is easily implementable. It allows scaling the power of optical phased arrays and does not require heavy optical elements. Equations for calculation of the optical scheme for implementation of the feedback loop are presented along with the experimental results on coherent combination of three beams.