Atmospheric and Oceanic Optics最新文献

Air temperature data at weather stations in the Northern Hemisphere and astronomical insolation data were ordered by increasing latitude and analyzed together for different samples between 1897 and 2010. Using a step-by-step regression of the latitudinal variation in the long-term average temperature to a polynomial of astronomical insolation, a latitudinal trend in the temperature determined by the Sun and fluctuating regression residuals, which characterize individual features of data, are identified. The absence of interaction of these components is numerically achieved for any samples. It has been found that the latitudinal trend in the long-term average temperature completely determines the warming and contributes about 82% to the total temperature dispersion in the Northern Hemisphere for available samples. The boundaries of regions where temperatures are above and below the latitudinal trend in the long-term average temperatures reveal known geographic structures, thus verifying the trend.

Electric discharge nitrogen lasers are popular sources of UV radiation commonly used in many scientific and practical applications. Up-to-date commercial nitrogen lasers should meet several requirements, such as small overall dimensions, high pulse-to-pulse stability, and long service life. In this work, a nitrogen laser excited by a pulsed longitudinal inductive-electric discharge which meets these criteria is suggested. As a result of the experimental studies, lasing at the wavelengths λ₁ = 337.1 and λ₂ = 357.7 nm is obtained. The generation energy attains 0.67 mJ at a pulse duration of 20 ns (FWHM) and a nitrogen pressure of 7–8 Torr. Nitrogen pumping only by a longitudinal discharge in an experimental setup with similar parameters decreases the lasing energy to 0.4 mJ (at the same pulse duration) at a nitrogen pressure of no higher than 5 Torr. Nitrogen lasers with these radiation parameters can be used in treatment of ophthalmic diseases and tuberculosis.

Development of laser technologies increases requirements for lasers being developed which generate narrow-band radiation at different wavelengths. In view of this, the importance of wavelength-tunable diode and vibronic lasers with broadband amplification circuits increases. A possibility of generating highly coherent radiation in a solid-state alexandrite laser using an original composite cavity which includes an additional external dispersive cavity is confirmed. Conditions for narrow-band (less than 20 pm) radiation generation in this cavity with a possibility of smooth tuning the lasing wavelength in the spectral range 740–780 nm are experimentally studied. Narrow-band lasing in an alexandrite laser with a radiation energy of 30 mJ and a pulse duration of 35 ns is shown. The created compact narrow-band alexandrite laser can be an effective alternative to parametric oscillators (OPO) and Ti:Sapphire lasers in lidar systems operating in the spectral range 700–850 nm.

The work studies the glow of diffuse plasma jets (DPJ), which make it possible to simulate some properties of red sprites, which are pulsed discharges observed in the upper layers of the Earth’s atmosphere at altitudes of 40–100 km, in low-pressure atmospheric air. DPJs are initiated by pulse-periodic capacitive discharge plasma created in a quartz tube between two external electrodes and simultaneously propagate in opposite directions. Two pairs of ring electrodes spaced 66 cm apart are used to generate DPJs which move towards each other. Bright areas of luminescence (BAL) similar to those observed in the lower part of column sprites appear when unipolar voltage pulses from generators are applied to each pair of ring electrodes with a delay of hundreds of nanoseconds. Air pressure of 1–2 Torr is shown to be optimal for the appearance of BAL at a generator voltage of 7 kV, and BALs are shown to appear due to the interaction of streamers which make up the DPJs. The speed of propagation of the DPJ front is measured for voltage pulses of positive polarity applied to the ring electrodes. Pictures of DPJs and BALs in them are made and their emission spectra are measured. Using the SPECAIR program, plasma parameters are calculated in different areas of DPJs. A decrease in the average electron temperature is found in the region where BALs appear. The results will be useful for studying the properties of red sprites.

Sudden stratospheric warming (SSW) significantly impacts the weather in the troposphere and the dynamics of the upper atmosphere. The definition of SSWs and their classifications have been formulated for a long time. However, early (in November – the first half of December) SSWs are understudied. In this work, the effect of early SSWs on a stratospheric polar vortex is studied based on JRA-55 and MERRA-2 reanalysis data. Early SSWs are determined in two ways, in terms of the zonal average temperature and the zonal wind component with and without the climatological norms of the component. Polar vortex response to SSW is represented by the geopotential altitude field. The variations in the surface temperature and surface pressure during displacement and splitting of a stratospheric polar vortex during an early SSW are also analyzed based on sounding data at polar stations in different continents.

When analyzing the propagation of optical radiation in a turbulent atmosphere, the structure function is a crucial tool. We propose to improve the method of its calculation by expressing the function analytically, via the mode coefficients of wavefront expansion. We derive formulas for the structure function on a circular aperture. Unlike the previously published analytical solution, ours correctly accounts for the entire aperture area. We compare our method to the previously published one and to numerical calculations with sufficiently fine discretization. Our test samples comprise Kolmogorov wavefronts, Zernike polynomials, and Karhunen–Loève functions corresponding to the Kolmogorov turbulence model. We show the deviation in results between our method and the others. Then, we explain the generality and other advantages of the new method. It enables an exact calculation of the structure function of a wavefront from its mode coefficients in problems of optical radiation propagation in randomly inhomogeneous media.

The thermodynamic state of the atmosphere and, in particular, the mesosphere, is determined by the wave structure. Noctilucent clouds are a good indicator of these wave processes. Photographic observations of noctilucent clouds in Yakutsk were used to analyze certain characteristics of the propagation of atmospheric waves. We were first to describe the observations of the so-called mesospheric bore in noctilucent clouds over eastern Siberia, recorded synchronously with two homotypic cameras. The height of the wave front determined by the triangulation method was 79 km. The case of video recording of the propagation of a few waves of different lengths in intersecting directions in noctilucent clouds on July 25, 2018, is analyzed. Analysis of the parameters of two waves propagating towards each other showed that the first had an average length of 53.5 ± 6.2 km, an average phase velocity of 98.4 ± 12 m/s, and moved northeast. The second wave of the scallop type with an average length of 14.8 ± 1.8 km propagated southwest with an average phase velocity of 61.5 ± 6 m/s. The speed of westward wind drift of all clouds was 67 ± 5 m/s. Our results will be useful for specialists in the field of physics of wave processes in the upper atmosphere.

The paper considers possibilities of taking into account data from lightning networks in the procedure for lightning data assimilation in numerical models of atmospheric dynamics. A universal procedure is suggested and implemented as a code within the WRF-ARW model. According to the data from lightning detection networks, cells of a computational grid are defined, where lightnings have been recorded. Then moisture is iteratively added in these cells until the occurrence of thermodynamic instability and, hence, convection. The effect of using this procedure on the forecast of precipitation, temperature, and humidity is studied, and the suggested procedure is compared with other lightning assimilation methods. The use of data from lightning detectors makes it possible to locally improve the forecast of heavy precipitation and temperature in areas where thunderstorms were observed. The Peirce–Obukhov coefficient increases from 0.26 to 0.40 when this procedure is used for forecasting heavy precipitation.

The influence of aerosol particles on the parameters of the global atmospheric electrical circuit is among important issues of the theory of atmospheric electricity. This paper presents a theoretical model of the effect of aerosol particles on the global atmospheric electrical circuit (GEC) under the fair weather. Surface aerosol is considered as a summand in the total columnar resistance. Electric field generators which support the GEC are taken into account through the boundary condition as the specified ionospheric potential. In addition to the theoretical model, experimental observations of electrical characteristics of the atmosphere and aerosol concentration are presented. The theoretical and experimental studies make it possible to estimate the concentration of submicron aerosol particles.

We present the results of trajectory analysis of long-term measurements of organic (OC) and elemental (EC) carbon in aerosols sampled on quartz filters at an altitude of 300 m at ZOTTO station. The EC and OC concentrations were determined by the thermo-optical method. The resulted time series were supplemented with the HYSPLIT backward trajectories, and CWT and PSCF functions were calculated on a grid of 150 × 250 cells, which covered the geographical area of 30° × 20° centered at Zotino. These functions characterize the intensity of potential sources of carbon-containing aerosols in a cell. The results make it possible to identify the regions with the strongest organic and elemental carbon emissions and to estimate the seasonal variability of these emissions. In particular, in summer, the main sources of OC and EC are located to the east of Zotino, in the Podkamennaya Tunguska River region, and are most likely associated with wildfires. In cold seasons, most sources of carbonaceous aerosols are in the southwestern part of the geographical region under study, where large cities are located and the bulk of the population is concentrated. The regression analysis of CWT functions of organic and elemental carbon is shown to enable determining the dominant type of carbonaceous aerosol sources in some cases. Our results can be used for estimation of aerosol radiative forcing in Siberia.