Estimation of Aerosol Radiation Effects under Background and Smoke-haze Atmospheric Conditions over Siberia from Empirical Data

The results of numerical simulation of downward solar radiation fluxes for background and smoke-contaminated atmospheric conditions are discussed. Vertical profiles of aerosol characteristics are obtained from the empirical model based on the data of aircraft sounding of profiles of angular scattering coefficients and content of absorbing particles in the lower troposphere. The background model was created using the results of measurements obtained under cloudless and mostly cloudless atmospheric conditions in 1999–2011. Optical parameters of smoke aerosol are determined from the data of aircraft measurements in the period of long-term wildfires in Siberia in the summer 2012. It is demonstrated that deficiency in diurnal values of total solar radiation at the surface level caused by the formation of the optically dense smoke layer as compared to background conditions, is more than 13 MJ/m².     

Unusual Solar Radio Burst Observed at Decameter Wavelengths

An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s^?1) at frequencies higher than 22 MHz and negative (100 kHz?s^?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈10³ s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.     

Stellar Evolution and the Cosmologial Supernovae Rates

We present the results of the population synthesis of the population ofthe supernovae progenitors. Both single and double degenerate progenitorsof SN Ia are considered. We compute the cosmic rate histories for SN I,SN II and both classes of SN Ia, and present them in the form of redshiftand magnitude distributions. These results can be compared with observationaldata, allowing to estimate the star formation rate history and thecosmological parameters including ω_baryons which cannot beestimated from analysing the Hubble diagrams of supernovae.We find that single degenerate (SD) SN Ia are younger than double degenerate (DD) ones, and so the SN Ia in elliptical galaxies should be mostly DD.We propose to use the redshift dependence of relative supernovae rates indifferent types of galaxies, or of different supernovae types forinterpretation of observations. These relative rates should be lessinfluenced by the selection effects than the absolute ones. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spread <Emphasis Type="Italic">F</Emphasis> in the Midlatitude Ionosphere According to DPS-4 Ionosonde Data

The results of studying spread F obtained from the DPS-4 ionosonde data at the observatory of the Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (Moscow) are presented. The methodical questions that arise during the study of a spread F phenomenon in the ionosphere are considered; the current results of terrestrial observations are compared with previously published data and the results of sounding onboard an Earth-satellite vehicle. The automated algorithm for estimation of the intensity of frequency spread F, which was developed by the authors and was successfully verified via comparison of the data of the digisonde DPS-4 and the results of manual processing, is described. The algorithm makes it possible to quantify the intensity of spread F in megahertz (the dFs parameter) and in the number of points (0, 1, 2, 3). The strongest spread (3 points) is shown to be most likely around midnight, while the weakest spread (0 points) is highly likely to occur during the daytime. The diurnal distribution of a 1–2 point spread F in the winter indicates the presence of additional maxima at 0300–0600 UT and 1400–1700 UT, which may appear due to the terminator. Despite the large volume of processed data, we can not definitively state that the appearance of spread F depends on the magnetic activity indices Kp, Dst, and AL, although the values of the dFs frequency spread interval strongly increased both at day and night during the magnetic storm of March 17–22, 2015, especially in the phase of storm recovery on March 20–22.     

Consistent patterns of the size distribution of thermokarst lakes

The purpose of this work is to study empirically the patterns of size distribution of thermokarst lakes within lacustrine thermokarst plains. Investigations were performed at 16 sites with various geomorphological, geocryological, and physical geographical conditions (Kolyma Lowland, Western Siberia, Lena River valley, Alaska). The accordance of the distribution area with the lognormal and exponential laws, and the accordance of the average diameter distribution with the normal law have been tested; the tested laws of distribution resulted from previous investigations. The results have shown that the lognormal law of distribution of thermokarst lake areas is valid for the vast majority of cases, and the other types of distribution are inconsistent with empirical data. This evidence favors the development pattern for lacustrine thermokarst plains, when thermokarst processes started simultaneously and the rate of lake growth was proportional to the density of heat loss through the side surface.     

On the effect of the coastal zone wind regime on the optical characteristics of haze

Based on an experimental study of directed dissipation coefficients and aerosol microstructure in the coastal area the problem of wind regime manifestation is considered. It is shown that the main changes of parameters of dissipation indicatrix form near angles =15°–165°, which are conditioned by submicron fractions of aerosol particles, take place without regard for wind regime. Usually they are defined by effect of relative air humidity. It is found that specific manifestations of wind regime are observed close to small dissipation angles and are conditioned by the effect of coarse-dispersed aerosol fractions.UDK 551.593     

Relationship between the observed and weakly-turbulent spectra of surface gravity waves

The theory for weakly-turbulent surface gravity waves normally identifies some auxiliary function (weakly-turbulent spectrum) with the actual (observed) wave spectrum. In this paper, a general formula for the relationship between weakly-turbulent spectra and observed spectra is derived, and a numerical calculation is provided to show the difference between them. In particular, violation of the exponential nature and angular distribution of weakly-turbulent spectra is noted, along with the occurrence of secondary peaks. Quantitatively, the weakly-turbulent spectra differ insignificantly from the observed spectra.Translated by Vladimir A. Puchkin.     

Diurnal rhythms of carbon dioxide concentration in the sea-level air layer and in the surface water of Lake Baikal in different hydrological seasons

Results of studying processes of gaseous exchange of carbon dioxide (CO₂) in the water surface-atmosphere system of Lake Baikal are considered. Measurements were carried out in the littoral of the lake near the settlement of Bol’shie Koty. The measurement point was selected for the following reasons. First, it is the place where water chemistry and biota have been studied for several tens of years. Second, by its meteorological conditions the place can be considered as background. It is shown that during all hydrological seasons the gas exchange of CO₂ in the Baikal water surface-atmosphere system has a well-pronounced trend, whose amplitude depends on the season. The data obtained are indicative of the main role that Lake Baikal biota plays in regulating the intensity of gas exchange.