Home – Home – Jornals – Atmospheric and Oceanic Optics 2020 number 4

The bank of spectral line parameters of the principal isotopologue of the hydrogen sulfide molecule (H₂³²S) is presented. The databank is based on the global simulation of the line positions and intensities of this molecule performed within the method of effective operators. The parameters of the global effective Hamiltonian and of the effective dipole moment operator were obtained by their fittings to, respectively, the observed line positions and intensities, taken from the literature. The databank covers the 552.76- 8424.32 cm^-1 spectral range and contains the calculated values of the following spectral line parameters: line position, line intensity, energies of lower and upper states, Einstein coefficient for the spontaneous emission, and the statistical weights of the lower and upper states. The intensity cutoff was chosen equal to 10^-28 cm/molecule at T = 296 K. In total, the databank contains about 88 thousand lines. This databank is deployed on the website of V.E. Zuev Institute of Atmospheric Optics SB RAS (ftp://ftp.iao.ru/pub/H2S/).

We compare the time variations in monthly average concentrations of black carbon in the surface atmospheric layer, obtained from field measurements ([BC]) and from MERRA-2 reanalysis ([BC]_M) at four monitoring sites located in the northern part of Russia (Tiksi Hydrometeorological Observatory (HMO), Pechora-Ilych Biosphere Reserve, Alaska (Barrow), and Greenland (Summit). It is shown that the MERRA-2 reanalysis data for the regions of Tiksi HMO and Barrow not fully reflect the [BC] variations during the year, in contrast to the Pechora-Ilych Nature Reserve, where the differences are within 30-50%. The [BC]_M reanalysis data for the Summit monitoring site qualitatively agree with the measurement data characterizing the BC content in the free troposphere, but they underestimate [BC] by more than 2 times. In general, the analysis showed that the results of the MERRA-2 reanalysis of the monthly average values of the surface concentration of atmospheric black carbon can be used for climate assessments for hard-to-reach northern regions in the warm season with an error of about 30%. Possible reasons for the differences between [BC] and [BC]_M are discussed for different seasons and observation sites.

The rates of CO₂ anthropogenic emissions are estimated for Saint Petersburg and Moscow megacities based on satellite CO₂ measurements by OCO-2 instrument. The CO₂ emission rates for Saint Petersburg amount to 80 and 74 t/km² per day on March 1, 2016, and May 12, 2018, respectively. The CO₂ emission rate for Moscow is estimated as 123, 179, and 186 t/km² per day for August 25, 2018, June 22, 2018, and March 26, 2017, respectively. The comparison of our results with the estimates for other megacities has shown that the emission estimates for Saint Petersburg are close to those for Los Angeles and Berlin, and estimates for Moscow are close to those for London. The estimation errors are mainly caused by the anthropogenic contribution, which varies from 30% to ~ 90%.

A methodology for studying seasonal variations in cloud parameters over the regions of Western Siberia using satellite data is presented. Five natural zones have been identified: tundra, forest-tundra, bogs, taiga, and forest-steppe. A combined “summer” and “winter” cloud classification has been introduced including 16 and 12 cloud types, respectively. An algorithm based on neural network technologies and fuzzy logic methods is used for cloud image classification. The results of analysis of seasonal variations in some parameters of various cloud types and their repeatability over the considered regions of Western Siberia based on MODIS satellite data for 2017 are discussed. The dependences found for seasonal variability of cloud parameters are in a good agreement with the known literature data that confirms high efficiency of the technique proposed.

The results of stratospheric aerosol observations at lidar stations of Roshydromet after the explosive eruption of the Raikoke volcano (Kuril Islands, 48.29° N, 153.25° E) in June 2019 are presented. By using direct trajectory analysis and observational data of the Caliop satellite lidar the aerosol trace in the stratosphere is revealed from the volcano around the pole to Western Siberia within a month after the eruption. The lidar measurements of volcanic aerosol from the end of July 2019 at the Roshydromet lidar stations in Obninsk, Znamensk, Novosibirsk, and Petropavlovsk-Kamchatsky are presented. Volcanic aerosol was observed in the layer from 13 to 18 km. The integral backscattering coefficient in the layer varied from the maximum (0,8-1,6) × 10^-3 sr^-1 in August-September 2019 to (0,2-0,3) × 10^-3 sr^-1 by the end of the year.

The results of calculating the mean intensity and the mean power of laser radiation backscattered by a remote atmospheric layer and detected in the source plane are presented. Behavior of the mean intensity and the mean power of laser echo signal as functions of the refractive turbulence strength, the inner turbulence scale at the different diffraction regimes at the transmitting aperture, and sizes of the receiving aperture are studied.

The UV (355 nm) eye-safe turbulent lidar BSE-5 designed for atmospheric turbulence studies is described. Lidar works on the effect of backscattering enhancement, which occurs when a light wave propagates twice in a random medium. The design of the device is based on the receiving and transmitting afocal Mersen telescope, which provides thermomechanical stability during long-term operation of the device. To reduce the size of the telescope, the edges of the main mirror were cut off, which are not used during the lidar operation. Lidar tests were conducted at Tolmachevo airport, during which the turbulence condition was continuously monitored over the runway and over the aircraft parking. The lidar confidently recorded a turbulent wake for any aircraft type during takeoff and landing. It was found that the track width is 50 m wide, and the lifetime of the intense artificial turbulent zone over the airfield is 2-3 minutes.

The transmission spectra and methane absorption coefficients are compared for different instrumental functions of the spectral distribution of laser power using different sources of spectroscopic information. An expert list of methane lines is compiled.

We present the experimental results on electric and magnetic fields generated under breakdown and pre-breakdown modes of pulsed laser radiation propagation along atmospheric paths. It has been established that quasiperiodic electric and magnetic fields (105-106 Hz, duration of 10-100 ms) are generated during propagation of ms CO₂ laser pulses in the atmosphere under breakdown and pre-breakdown modes. The strongest induced electric and magnetic fields are observed at the number of breakdown centers per unit path length N_Nh = 0.17 m^-1. The connection of electric and magnetic fields arising around the ionization channel with the atmospheric parameters is shown.

A basic platform for photodetector modules used in the lidar complex for recording backscattered radiation in the near-infrared region is described. High-voltage pulse noise of DC/DC converters in the photodetector modules are reviewed and tested. A method is proposed for compensating the noise generated by such converters. The tests carried out in the lidars of Institute of Atmospheric Optics SB RAS showed the effectiveness of the module designed to record signals in analog mode at a wavelength of 1064 nm.

Relations and calculation results are presented for determining the effective thickness of the deposited water vapor layer and the effective optical path length adjusted by the absorption capacity of carbon dioxide to the surface layer, taking into account the sphericity of the earth's surface for the operation of infrared optoelectronic systems on slant paths at elevation angles of less than 20°.

The first results of comparative measurements of altitude profiles of concentrations of carbon dioxide and methane from the aircraft laboratory YAK-42D "Roshydromet" are presented. The data were obtained both in real time using devices operating on the basis of diode laser spectroscopy and in laboratory conditions with the use of a Fourier spectrometer by processing air samples collected in special flasks during research flights.