Vol 30, No 6 (2017)

A method for parameterization of the UV radiation absorption by atmospheric ozone is described. Parameterizations are suggested for computer simulation of tropospheric fluxes of UV–A and UV–B radiations and modified fluxes of biologically active UV radiation in medical applications (for the analysis of vitamin D formation and risk of erythema, cancer, and cataract). The parameterizations allow the solution of the UV radiation transfer equations at a single effective spectral point for obtaining integral fluxes in the 280–400 nm range (taking into account the spectral factors characterizing biological effects). When using the parameterizations, the characteristic errors in the calculations of the fluxes in a clear and cloudy troposphere are ~3–5%. The use of these parameterizations is relevant for fast radiation models, for example, on-line simulation of UV radiation fluxes for medical purposes. This method can be used to improve the accuracy of radiation codes in general atmospheric circulation models, radiation-chemical models, etc.

The study of cirrus clouds, which significantly affect the climate, is carried out using lidars. Interpretation of the lidar data is based on the direct solution of the problem of light scattering by particles of crystal clouds. Optical characteristics of perfect ice hexagonal columns, obtained previously, poorly agree with the lidar observation results. The work describes calculations of the optical characteristics of irregular hexagonal ice columns, which are in a good agreement with the experimental results. The calculations for particles with deformation of a dihedral angle of 90° are presented. It is shown that the logarithm of the scattering matrix can be linearly approximated well by the logarithm of the particle size. This can significantly accelerate the calculations of the optical characteristics of clouds. It is ascertained that the optical characteristics are in a good agreement with the lidar observation results throughout the range of sizes calculated even at deformation angles of a few degrees.

Trends of total CO and CH₄ contents are estimated from satellite AIRS spectrometer data for the Eurasian domain (0–180° E, 0–85° N) for different time periods and seasons. The results are compared with similar estimates, obtained from ground-based spectroscopic measurements at seven stations of the European Network for the Detection of Atmospheric Composition Change (NDACC) and at measurement sites of the Institute of Atmospheric Physics, Russian Academy of Sciences (Zvenigorod Scientific Station (ZSS), Zotto, and Beijing) and St. Petersburg University (Peterhof), located in the study domain. Overall, the total CO decreased over northern Eurasia during the period of 2003–2015 at a rate of 0.05–1.5%/yr, depending on the region; while the total CH₄ increased at a rate of 0.16–0.65%/yr. Since 2007, the total CO has been increased during summer and autumn months in most mid- and high-latitude Eurasian background regions, and the total CH₄ growth has been accelerated. Changes in the global photochemical system, proceeding against the background of global climate change and, in particular, changes in the “sources/sinks” ratio for minor atmospheric admixtures are suggested as possible causes of this dynamic of trends of the atmospheric CO and CH₄ contents.

A model is used to estimate black carbon (BC) concentrations in air over different regions of the Russian North in 2000–2013. We discuss different BC physical sources in the atmosphere (anthropogenic sources and wildfires), emissions from these sources on the territory of Russia (according to different data), and estimate their contributions to BC concentration in air over Russian Arctic regions during winter and summer. This is done using satellite data on BC emissions to the atmosphere (GFED, MACCity, and others), as well as our estimates based on official statistical data of the Russian Federation. Long-range BC transport in the atmosphere was analyzed by the method of back trajectory statistics of air mass transport, developed previously using ARL NOAA data (HYSPLIT model). In the near-ground air over northern regions of the Russian Federation, the contributions of anthropogenic BC sources predominate over those from wildfires even during summer (except in Ust-Lena Nature Reserve), when contributions from remote anthropogenic sources are minimal. Average BC concentrations in air along the coast of the Arctic Ocean vary by two orders of magnitude, with the maximum in the region of Nenets Nature Reserve (the main source is nearby flares from casing-head gas combustion in regions of active hydrocarbon fuel production). The BC concentrations in air show large interannual and interseasonal variations; therefore, estimates according to multiyear average indices bear little information. Thus, measurements of BC content in air over a single site during one season or even one year should not serve a basis for long-term conclusions and forecasts pertaining to the entire region.

Results of measurements of the black carbon and fine aerosol content in Beijing and in a background region 150 km to the northeast of the capital of China are analyzed. The measurements have been carried out for many years, mainly in autumn periods. A regional decrease in the black carbon concentration has been found. The conclusion made in earlier works about the decrease in the relative contribution of soot aerosol, on average, with an increase in air turbidity has been corroborated.

We explore how the microstructure parameters of atmospheric aerosol can be estimated from regression equations that describe their relationships with spectral measurements of the aerosol optical depth (AOD). Special attention is paid to the problem of estimating the volume concentration, total cross section, and mean radius of coarse aerosol particles. This problem is topical because of large errors arising when an insufficiently wide spectral range of measurements is available to retrieve these parameters using directly the AOD inversion. Estimates of the coefficients of simple and multiple linear regressions are presented together with the results of their use to retrieve the parameters of coarse-mode aerosol from data of sun photometer measurements in Tomsk.

The results of comparative experiments on measurements of the crosswind velocity by the passive correlation optical method and with a coherent Doppler wind lidar are analyzed. The passive correlation optical measurements were carried out with a crosswind velocity meter developed at the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (IAO SB RAS).

Results of measurements of the parameters of aircraft wake vortices by a Stream Line coherent Doppler lidar during the three-day experiment on the airfield of Tolmachevo Airport are presented. The spatial dynamics and evolution of the wake vortices generated by landing aircraft of different types, from Airbus A319 passenger aircraft to heavy Boeing 747-8 cargo aircraft, are analyzed. It is shown that Stream Line lidars may be used to receive reliable information about the presence and intensity of aircraft wake vortices in the vicinity of а runway.

We present experimental results on the remote detection of surface traces of some high-energy materials using a Raman lidar designed on the basis of an excimer KrF laser with a narrow generation line and a multichannel spectrum analyzer based on diffraction a spectrograph and time-gated ICCD camera. The sensitivity of the system is evaluated for a detection range of 10 m. A detection limit is attained for the traces of nitrogen-containing chemical materials with a surface density of 0.5 μg/cm² at a signal accumulation of over 1000 laser pulses.