Home – Home – Jornals – Atmospheric and Oceanic Optics 2021 number 5

High sensitivity spectra of the main ozone isotopologue were recorded using a cavity ring-down spectrometer in the region 7920-8670 cm^-1 covering the range up to the dissociation threshold and above. The sensitivity on the order 2 × 10^-11 cm^-1 was achieved. This makes it possible to detect high energy combination bands up to ten vibrational quanta in the electronic ground state. Line positions and intensities are measured for these bands. Vibronic hot bands of the ¹⁶O₃ borned by transitions from the (100) and (020) electronic ground state levels to the excited ³ A ₂ triplet state were recorded for the first time providing new information about the dependence of predissociation broadening on rotational quantum numbers.

Self- and air-broadening coefficients of nitrogen dioxide lines are calculated. The calculations are performed at a room temperature ( Т = 296 K) for ~ 29000 lines, rotational quantum numbers vary in the range up to 87 for N and up to 20 K_a . The temperature exponents are calculated for every line. The resulted parameters are compared with the literature and spectroscopic database. The calculations are made by two approaches: the semi-empirical method and energy difference method.

The peak positions and half-widths of the Q -branch of the n₁ band, as well as the ratios of intensities of the Q -branches of n₃ and 2n₂ bands of methane in a methane-helium mixture are measured at various pressures and concentrations. An empirical model has been developed for estimation of the helium concentration in a methane-bearing medium by measuring these spectral parameters. The error in the He concentration is found to be less than 1% when using the n₁ band half-width. The ways of developing this technique and increasing its accuracy are considered.

Experimental results are presented for self-broadening and shift of six isolated absorption lines of CO₂ versus pressure in the 1.6 mm spectral range at a room temperature. The measurements were carried out at a high-sensitivity high-resolution diode laser spectrometer with a signal-to-noise ratio of 3000 to 7000. To describe the experimental spectra, five theoretical line profile models VP, RP, qSDRP, qSDVP, and qSDVP + LM were used. A strong influence of weak closely spaced lines on the parameters retrieved (intensity and collisional broadening coefficient) of strong lines was found, as well as nonlinear pressure dependence of narrowing parameter for RP and qSDRP line profile models. The linear pressure dependence of the parameters retrieved for qSDVP + LM line profile is shown in the range from 0.001 to 1 atm.

Choice of the parameters of the lens raster in a Shack-Hartmann wavefront sensor with the minimal residual error in the wavefront reconstruction is one of the solutions to the problem of the sensor measurement accuracy. This paper presents the results of numerical experiments on estimating the accuracy of reconstruction of the wavefront distorted by atmospheric turbulence taking into account the transfer functions between the telescope and the sensor and between the raster and the photosensitive matrix of the receiving device.

Experimental results of comparison of two methods of multielement analysis of liquid-droplet aerosol based on spectral analysis of laser plasma radiation are presented. The features of the emission spectra of laser plasma arising as a result of laser breakdown (LIBS method) and of filamentation (R-FIBS method) in liquid droplet aerosol are investigated. A liquid-drop aerosol containing a Na solution is used. The experiments were carried out to determine the optimal use of the methods on mobile platforms. It is shown that, for both methods, there are optimal delay times of the start of signal registration relative to the start of plasma generation, at which the maximal signal-to-noise ratio is observed. The magnitude of these delays differs by three orders of magnitude when going from nanosecond to femtosecond pulses. For the LIBS method, the dependence of the signal-to-noise ratio was obtained for various focusing of laser radiation deep into the liquid-droplet cloud. The values of the Na limit of detection for both methods are determined.

We analyze the annual variations in the total ozone content (TOC) over Tomsk in period of 1994-2017 and integrated aerosol backscattering coefficient (IABC) in the period 2000-2016 obtained using M-124 ozonometer and lidar method, respectively. The correlation coefficient between these time series turned out to be -0.23, indicating that, although localized in the same altitude range, these time series are uncorrelated. Study of annual behaviors formed from these time series showed that TOC can be fitted by the function sin, while IABC, by the function cos. At the same time, both functions depend on a single parameter, i.e., the time in decades. This allowed us to conclude that the variations of these atmospheric constituents are formed mainly in two perpendicular directions. It is found that the annual behaviors of TOC and IABC consist of two sections, fitted by exponential curves.

This paper presents a study of the temperature of the mesopause region (~ 87 km) by measuring the emission of OH (3-1) at high latitude station Maimaga (63.04° N, 129.51° E) and comparing the results with the temperature data Aura (MLS) at 0.002 hPa during 2013-2018. The average rotational temperature of OH (3-1) was compared with Aura (MLS) measured temperatures ( T ) and the background temperatures ( T _bg) calculated from them. The obtained result indicates in favor of more correct comparison of the temperature OH (3-1) and temperature T _bg calculated from Aura (MLS) data. Comparison of the data mutually confirms the observation of elevated temperatures in the mesopause in the winter period 2014-2015. In the winter periods of 2013-2015, the seasonal course of the temperature OH (3-1) is ~ 10 K higher than the seasonal course of the temperature T _bg. During the winter periods of 2015-2018, although the temperature variations are close in value, the seasonal course of the temperature OH (3-1) continues to exceed the values of the seasonal course of temperature T _bg. In general, the temperature variations measured by two different methods are qualitatively consistent and reflect the nature of seasonal changes. Temperature differences can be explained by many factors, such as differences in measurement heights and methods.

The average annual temperature derivatives analysis was carried out according to the data of 927 weather stations of the Northern Hemisphere for the period 1956-2016. Changes in derivatives are considered as manifestations of the emergent property of a holistic climate system. A measure of these manifestations has been introduced. The measure has a functional form, including averaging positive and negative derivatives and calculating the correlation coefficients along weather stations. The extrema of the derivative temperatures are determined; it is found that the sample distribution of the sums of the opposite extrema of the derivatives is symmetric and has a greater kurtosis than the normal distribution. In the study period, the values of the measure are already close to their limiting values. At that, the climate system's equilibrium state is preserved, while regional fluctuations of individual climate elements have increased. Therefore, an annual assessment of changes in the multichannel monitoring system's measure of emergent properties is required.

Air-sea CO₂ exchange over the Gulf of Finland according to SOCOM ship measurements during March and April 2019 have been assessed to determine the possible impact of the water surface on estimates of St. Petersburg anthropogenic emissions. It was found that the surface of the Gulf of Finland is a source of CO₂ in March and a sink in April 2019. CO₂ fluxes per unit area of the water surface of the Gulf of Finland were on average significantly smaller (by 1-2 orders) than the anthropogenic emissions of St. Petersburg. Contribution of the Gulf of Finland surface to CO₂ content of air masses passing over the water surface in March-April 2019 was small on average in comparison with the contribution of St. Petersburg according to EMME (Emission Monitoring Mobile Experiment) measurements and ODIAC data (less than 1% of the cities contribution). For extreme wind speeds above the water surface and differences in the partial CO₂ pressure in water and air, the contribution of the Gulf of Finland to the CO₂ content of the air masses can reach almost 3% in relation to the anthropogenic contribution of St. Petersburg.

We show a possibility of measuring wind speed with a lidar and a sampling method developed. An experimental setup operating at an eye-safe 0.355 mm wavelength is described; corresponding measurement data are presented. The dependence of the measurement quality on optical properties of the atmosphere is analyzed. The mean absolute errors are 1.05 m/s for the wind speed and 13.3° for the wind direction calculated with accumulated measurements for spring-autumn is.

The paper describes the multi-conjugate adaptive optics systems and identifies the features of optical conjugations of adaptive mirrors with turbulent layers for ground-based solar telescopes. The optimal size of the field of view for a solar telescope operating under average atmospheric conditions has been calculated. The size of the optimal field of view is equal 10 arc. sec. Recommendations are given for the development of MCAO systems for ground-based solar telescopes. The concept of a system for determination of 3D wavefront distortions for the Large Solar Telescope LST-3, as well as for the wavefront registration in the Large Solar Vacuum Telescope, is proposed.