Atmospheric and Oceanic Optics最新文献

Based on the results of a comprehensive experiment conducted in September 2020, the spatial distribution of the following trace gases over the seas of the Russian Arctic are analyzed: carbon monoxide (CO), ozone (O₃), nitrogen oxide and dioxide (NO and NO₂), and sulfur dioxide (SO₂). It is shown that the gas concentrations in the surface air layer over the seas (at an altitude of 200 m) vary in the range 18–36 ppb for O₃, 60–130 ppb for CO, 0.005–0.12 ppb for NO, 0.10–1.00 ppb for NO₂, and 0.06–0.80 ppb for SO₂. The distribution of the gases over the water area is heterogeneous over most seas, which most likely reflects differences in their uptake by the ocean and peculiarities of transport from the continent.

A technique for parallel recording of lidar signals in the photon counting and charge accumulation modes at the Siberian Lidar Station (SLS) of the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, is described in detail. A device for signal detection at the unique SLS lidar with the use of the combined technique is designed and experimentally tested. During the experimental testing of the device, the limits of applicability of the suggested technique to atmospheric temperature vertical profiling based on lidar signals of pure rotational Raman spectra are determined. The comparison between the lidar and satellite measurements shows their good agreement, which proves the high efficiency of the combined technique and confirms a possibility of atmospheric temperature profiling based on the SLS primary mirror throughout the altitude range of the SLS Raman lidar.

The chemical composition of atmospheric aerosol sampled at the Cape Baranov Ice Base research station (Severnaya Zemlya archipelago) in 2017–2022 is studied. The interannual and seasonal dynamics of ions and trace elements in the aerosol composition is analyzed in detail. A 1.5-fold increase in the annual mean total ion concentrations is traced. The growth of the sum of ions was mainly due to the concentrations of Na⁺ and Cl⁻ ions of marine origin, the content of which is minimal in summer and maximal in winter. The variations in the concentrations of nonmarine ions ({text{NH}}_{4}^{ + },) K⁺, Ca²⁺, F^–, ({text{NO}}_{2}^{ - },) and ({text{NO}}_{3}^{ - }) differed from the seasonal course of Na⁺ and Cl⁻ concentrations: the former decreased during the transition from winter to spring and increases in summer with a subsequent decrease in autumn against the background of an increase in the sum of ions due the marine ions. The ion composition of aerosols is formed under the effect of the marine factor, air mass transport, underlying surface, and wildfires. Among trace elements, Fe, Al, Zn, Mn, Sn, Cr, and Cu dominated with high concentrations in the fall and winter periods. Based on enrichment factors, elements of terrigenous (Al, Ti, Mn, Fe, Th, and U), mixed terrigenous and nonterrigenous (Li, Be, V, Co, Sr, and Ba), and nonterrigenous origin (Ni, Cu, Zn, Cr, Mo, Mo, W, Ag, Tl, Pb, As, Se, Cd, Sn, and Sb) are identified. The highest contribution to the total level of air pollution is made by Fe and Mn in winter and autumn and by Fe and Be in spring and summer. Among nonterrigenic elements, Cu, Sn, Zn, Se, and Ni contributed the most in all seasons. The level of air pollution with trace elements is assessed as low at the Cape Baranov Ice Base station.

To solve general and special problems of ground-based monitoring of the atmospheric electric field, it is necessary to identify global factors against the local variability of the monitoring data. The global unitary variation in the ionospheric potential observed in the daily variation in the electric field is distorted under the electrode effect near the Earth’s surface. The structure of the resulting electrode layer strongly depends on the degree of turbulent mixing, the specific conductivity of air, and the altitude of electric field measurement. Based on the equation for the total electric current, which follows from the theory of the electrode effect of the surface air layer, we simulated daily variation in the electric field at different altitudes under different meteorological conditions. The simulation reveals the dependence of the position and magnitude of the global extreme points of the electric field on the turbulent mixing coefficient, air conductivity, and electrode layer height. Our results can be useful for solving applied problems in geophysics, in particular, atmospheric electric field monitoring.

A single thundercloud which was developing near the coast of the Gulf of Finland at night is studied. Using three meteorological radars, two lightning detection systems, and a 3D numerical model, the physical processes which caused electrification of the cloud are analyzed. It is shown that the first lightning occurred in the period when a small area with graupel particles was observed in the upper part of the cloud. According to radar observations and numerical simulation, updrafts played an important role in the formation of that area and the microstructure of the cloud. Further increase in thunderstorm activity was associated with an increase in the cloud volume with graupel and hail. Analysis of the charge values of individual cloud fractions derived in numerical simulation shows hailstones to be the main carriers of a negative charge.

Remote control of high-intensity laser beams in the atmosphere is an important problem of atmospheric optics. It is of special interest for atmospheric sounding, where turbulence can affect beam propagation. We experimentally study the effect of a turbulent layer produced at the beginning of a laser radiation propagation path on the characteristics of the filamentation domain and generation of high-intensity plasma-free channels for laser beams 2.5 and 5 cm diameter, including under the phase control of the transverse beam structure with a deformable mirror. In the presence of turbulence, the beginning of multiple filamentation domain approaches, however, insignificantly (<10% of the path length), a radiation source. More important is that a turbulent layer formed at the beginning of a path results in a multiple increase in the number of high-intensity (mean intensity is ∼10¹¹–10¹² W/cm²) light channels in a laser beam during its nonlinear propagation, which induce two-photon fluorescence of dyes at a distance of longer than 100 m from the radiation source with the signal level sufficient for its recording by a lidar scheme. This laser beam structure can be used for sounding natural and anthropogenic aerosols.

Contributions of anthropogenic and wetland methane emissions in Northern Eurasia (>40° N) and Russia into the near-surface CH₄ abundance are quantified using GEOS-chem global chemical transport model at ZOTTO, Teriberka, and Tiksi measurement sites. Numerical results agree well with the proposed semianalytical solution, in which the total contribution (atmospheric response) in the CH₄ level at a given site is decomposed into direct (synoptic) and global terms. On an advection timescale corresponding to a synoptic time interval, the annual average direct contribution of Russian anthropogenic emissions into the CH₄ mixing ratio measured at ZOTTO (38.6 ppbv) is more than twice as large as that for Western Europe sources (17.7 ppbv). For the Arctic sites, the anthropogenic inputs from Russian and European sources are roughly similar (19.5 and 12.4 ppbv, respectively). The input from continental sources into near-surface methane abundance and its annual variations at the Arctic sites are generally lower compared to those at the ZOTTO site due to larger transport times from upstream CH₄ source regions. Model-based atmospheric responses in methane levels at the Teriberka and Tiksi sites to continental CH₄ sources are found to be very close owing to the relatively homogeneous (circumpolar) spatial distributions of the anthropogenic and biogenic signals at high latitudes.

The results of experiments in the Large Aerosol Chamber of RPA Typhoon revealed the appearance of new aerosol particles larger than 15 nm in an aerosol-free volume of atmospheric air isolated from the external environment in darkness 20 min after the air purification. The generation of new particles is associated with the possible presence of precursor gases in the atmospheric air, which, under the influence of cosmic rays penetrating into the chamber, turn into aerosols. The experimentally observed evolution (over several days) of the size spectrum of the resulting particles shows that the generation of new aerosol particles lasts no more than 20 hours. During the evolution, the particles become larger and reach more than 100 nm size. After repeated purification of the air inside the chamber with the removal of newly generated aerosols, no new particles were detected for 10 days.

Calculation results are presented which show how optical radiation energy is redistributed and the law of conservation of energy is fulfilled when radiation is reflected from a specular surface in a turbulent atmosphere. We have ascertained that if spatially limited light beams are formed due to reflection, then the energy is redistributed in a plane transversal to the light propagation direction near the strictly backward direction within a limited region no larger than several Fresnel zones. In the case of a point reflector, where a spatially unlimited reflected wave is generated, the energy redistribution occurs on a much larger scale. An increase in the mean intensity of a reflected wave within a limited region with a diameter of two Fresnel zones around the strictly backward propagation direction (backscatter enhancement effect) occurs due to the outflow of reflected wave energy in lateral directions from a huge domain, which is several orders of magnitude larger than the area where this energy is accumulated.

Based on the analysis of high-resolution FTIR spectra recorded at the atmospheric monitoring station of St. Petersburg State University during 2009–2022, a possibility of deriving the NO₂ tropospheric column from ground-based measurements of direct solar radiation in the mid-IR range is studied. The best agreement (correlation coefficient r = 0.68) with simultaneous DOAS measurements of the NO₂ tropospheric column at the same monitoring station is provided by a retrieval technique based on the use of the spectral range 2914.30–2914.85 cm⁻¹ in combination with the Tikhonov–Phillips regularization. It is shown that FTIR measurements make it possible to reliably detect high levels of tropospheric NO₂ at the SPbSU monitoring station. Our results can be used at the FTIR stations of the NDACC network for significant expansion of the geography of tropospheric NO₂ monitoring.