Home – Home – Jornals – Atmospheric and Oceanic Optics 2021 number 1

Application of four algorithms developed for detecting optical vortices in problems of singular optics is considered. Structure of numerical models and design of corresponding computational application are described; input parameters required for the model implementation are listed. Special attention is devoted to precision of vortex coordinates and number. Depending on these characteristic, suggestions are made for possible application of the algorithms: two of them can only be used in theoretical studies, while other two can be applied in real laboratory experiments.

The 3-0 absorption band of carbon oxide and the 2 0 0 13^{- 0 0 0 01 band of carbon dioxide, confined in aerogel, were recorded using a Bruker IFS 125HR FTIR spectrometer. The parameters of spectral lines are obtained, their dependences on rotational quantum numbers are presented. The parameters we found are compared with those for the 2-0 band of carbon oxide and the 0 00 11 - 0 0 0 01 band of carbon dioxide taken from literature.}

The H₂O absorption lines broadened by air pressure were recorded in the 5900-6100 cm^-1 spectral region with the use of a Bruker IFS 125 HR spectrometer. The intensities and broadening and shift coefficients of H₂O absorption lines are retrieved for Voigt profile and modified Voigt profile which takes into account the dependence of the broadening on the speed of colliding molecules. The atmospheric transmission is calculated with use of H₂O line parameters from different versions of the HITRAN and GEISA spectroscopic databases and our new data. Model spectra are compared with atmospheric solar spectra measured with a ground-based Fourier spectrometer. It is shown that the use of our new data on H₂O absorption line parameters improves the agreement between the model and measured atmospheric spectra.

In order to study the capabilities of a turbulent lidar, an experiment was conducted using the BSE-4 system, a meteorological measuring system, and an MTP-5 temperature profiler. The profile of the structure constant of the refractive index C_n² up to an altitude of 2 km was determined using the lidar at an interval of 15 seconds. Experimental data on the intensity of dynamic turbulence when the wind increases over rough terrain are presented. Lidar operation under buoyant convection conditions allowed us to observe the movement of thermals and the formation of Cu clouds in the boundary layer. Under the conditions of cellular convection, the lidar recorded quasi-periodic oscillations of C_n² (Benard cells), which represented a stationary wave. Under stable temperature stratification, when the Richardson number was less than 1/4, the turbulent lidar detected the appearance of a Kelvin-Helmholtz wave.

Daily total precipitation amount and surface wind characteristics were retrieved for St. Petersburg and 15 stations of the Leningrad region for the period 1994-2018. Gradient boosting method was used to retrieve the precipitation data. The analysis of the data series retrieved has allowed us to ascertain the following effects of St. Petersburg megalopolis on the fields of the meteorological parameters: an increase in precipitation on the leeward side of the megalopolis and a decrease in the wind speed on the leeward side of the megalopolis and immediately at the city center. The criteria for their detection on a specific day (time) are developed; the average values of the effects are assessed.

The conditions for the formation are considered and the short-term forecast accuracy is estimated for six convective hazardous weather events or outbreaks occurred in the Urals and eastern part of European Russia in the warm period of 2020. Information on large hail, heavy rainfall, squalls, and tornadoes has been compiled from several data sources; it includes data from weather stations, damage reports, and analysis of forest cover disturbances based on Sentinel-2 satellite images. The short-term forecasts were derived by the ingredient-based approach based on GFS and GEM global atmospheric models and explicit simulation of convection using the WRF mesoscale atmospheric model.

An optical circuit is designed for the ring cavity of an optical parametric oscillator (OPO) based on two series-mounted active elements-mercury thiagollate crystals (HgGa₂S₄) with the radiation tunable in the near and middle infrared ranges 4.75-9.07 μm. The dependences of the radiation idle wavelength on the phase-matching angle and of the distribution of the IR OPO output radiation intensity on the idle wavelength are calculated. A possibility of narrowing the spectral width of the output radiation by introducing a dispersing element (Fabry-Perot etalon) into the cavity is considered.

We analyze the remote sensing reflectance spectra of seawater measured from the shipboard in the area of the Urals oil spill in the form of emulsion and individual films on the sea surface. The pollution was detected in the Bering Sea near Navarin Cape on August 4, 2013, during the voyage of the training ship "Professor Khljustin". In situ data from flow-through fluorometric measurements of the chlorophyll a and colored dissolved organic matter concentrations at a depth of 4 m, not influenced by contamination detected, were also used. The regression relations between remote and in situ measurements in clean and oil-polluted waters are analyzed. A preliminary version of the technique for detecting oil pollution on the sea surface, which is in emulsified form and in the form of small films of about 1 m² in area, is developed on the basis of remote measurements of the seawater spectra.

A new cavity ring-down spectrometer is designed for the near-infrared spectral region from 745 to 775 nm (12900-13400 cm^-1). A test spectrum is presented for the dioxygen rovibrational lines in a narrow spectral range near 13165 cm^-1. The sensitivity on the order of 1.7 × 10^-10 cm^-1 is attained.