This paper presents the results of the analysis of the dynamics of the temperature regime in the lower and middle atmosphere in Central Yakutia during the maximum development of major sudden stratospheric warmings (SSW, ± 10 days) in the period 2004-2019. The days of the maximum development of major SSWs were determined according to the database of the Chemical Sciences Laboratory (CSL / NOAA). The database of the Global Systems Laboratory (GSL ESRL / NOAA) on radio sounding of the atmosphere (Yakutsk airport station, 62.08 N, 129.75 E, 103 m above sea level, index of the World Meteorological Organization - 24959) was used. When analyzing the dynamics of the temperature regime, we considered the radio sensing data relating to 24:00 h. Additionally, we used temperature profiles at isobaric heights from 1000-1 hPa (37 levels in height) according to the ERA-Interim reanalysis data with a latitudinal-longitudinal resolution of 1 x 1 degree. It was revealed that there was a high correlation (R>0.8) between the temperature profiles according to the data of radio sensing of the atmosphere and the ERA-Interim reanalysis. Spatio-temporal maps of the temperature regime at isobaric heights of 50 and 10 hPa were constructed according to the ERA-Interim reanalysis data. In general, for the period under consideration, the boundaries of the tropopause heights during the maximum SSW development were in the range from 7,301 to 10,200 m, and the average tropospheric temperature was from -42.7 to -29°C. Linear and polynomial trends in the mean tropospheric temperature and temperature at isobaric heights of 50 and 10 hPa were used to determine the growth and decline trends (troughs and ridges). It was revealed that the temperature regime of the stratosphere at the level of 50 hPa before and after the maximum development of major SSWs demostrated, in general, a general growing trend, with the exception of the events of 2006-2008, and at the level of 10 hPa - growth or decline. The dynamics of the temperature regime of the lower and middle atmosphere in Central Yakutia was of a regional (local) nature and depended not on the period (day) of maximum development, but on the location and periphery of the SSW.

Climate anomalies are signicant deviations of certain meteorological elements from the climate norm. The cause of climate anomalies is large-scale deviations from the standard conditions of atmospheric circulation. The studied part of the Republic of Sakha (Yakutia) (north-east of Russia) is located in a zone of sharply continental climate, with very cold long winters, relatively hot short summers, short off-seasons and with large annual temperature amplitudes. From November to March, the territory is under the infiuence of the Asian Anticyclone. During the cold period, the anticyclonic type of weather prevails - very low temperatures, low humidity, little or no cloud cover, weak winds or calm. The usual weather pattern is occasionally disrupted by the arrival of warm air masses. There is a signicant increase in temperature, which then just as quickly returns to the background values. The authors set the task to study the synoptic conditions for the formation of sharp inter-day temperature changes in the territory of the Republic of Sakha (Yakutia). The dates of the beginning and end of the cold period are calculated and the analysis of the repeatability of the number of cases with a signicant difference in the average daily temperature in the cold half of the year for a number of weather stations is made. The characteristic synoptic situations for days with signicant day-to-day variability of air temperature are highlighted.

For the first time, a fire hazard assessment based on climate data was carried out in the forests of Gorny District, Sakha Republic (Yakutia). According to the statistical data of Gorny District, the damage from forest fires is shown in rubles, the area of harems for the years 2010-2020, the causes of their occurrence, which are reflected in the tables and diagrams of the study. Forest fires, according to the study and analysis, occur mainly up to 80 % of dry thunderstorms in hard-to-reach places and partly due to human fault. In the last part, in the results of the study and discussion, an assessment of the fire danger and the number of forest fires in Gorny District in the period 2010-2020 is given, which reflects interesting data that the amount of fire danger in the study is directly proportional to the number of forest fires. Thus, we found out that most forest fires occur due to the climatic characteristics of a certain territory. Here we see that the number of dry days affects the level of forest fires. We assume that forest fires can occur on dry sunny days-from lightning discharges into dry trees, as well as into grasses, from focusing the sun’s rays on dry grass in the summer. Here we get an interesting analysis: until 2015, when agricultural fire was allowed in Russia, the number of forest fires in hard-to-reach areas in Gorny District was much less, and when agricultural fire was banned throughout Russia, including Yakutia, the number of forest fires in Gorny District doubled. Making a conclusion, we put forward a hypothesis for the prevention of forest fire in remote areas of Russia, Yakutia, that it is necessary to allow controlled agricultural fires in spring and autumn to minimize the amount of dry grass in the fields, undergrowth, which eventually become like gunpowder, can even ignite from the sun ray, as well as forestry in the field to cut down lonely dry and old trees, remove dead wood in the forest, make mineralized strips in the forests.

Utilization of kinematic models for interpretation of experimental data in the sphere of photocatalitic removal of water pollutants make it possible to optimize the photoreactor system in order to reach the sufficient volume of photo reactor and to minimize the part of reactor which is not illuminated. The simple models of kinetics of zero and the first order are quite enough for describing and modelling the process of photomineralization of organic compounds. There are some photocatalitic processes of non-linear character and that cannot be described by a kinetic equation of the pseudo first order. The article set the task on optimization of group realization of photocatalitic process in any fixed time in heterogeneously polluted medium where the level of pollution in sites of water probes collection composed the linear regularized set. The purpose of the article was (1) forming a generalized non-linear model of process of photocatalitic clearing of water; (2) optimization of group process of water clearing process at the territory characterized by heterogenic level of water pollution. Conditions for utilization of kinematic equation of the pseudofirst order for optimization of photocatalitic clearing of pollutants in heterogeneous water media were analyzed. To solve the optimization task, the specifics of group process of photocatalitic clearing in heterogeneous media is to be taken into account where the functional dependence between major technological parameters occurrs and some limitation condition is to be applied. The physical meaning of additionally introduced limitation condition in regard of major technological parameters is that resources usable for realization of group method of photo catalyze are limited. In view of above the space of possible functions usable for said functional dependence decreased. The parametric method for optimization of group catalytic process including limitation condition imposed on searched optimum function is suggested. The model solution of task on minimization of rest pollution at the given moment is given using method of non-conditional variation optimization.

The leaf area index (LAI) and phytomass are major parameters characterizing net primary production, which could be determined by methods of remote sensing of vegetation crown. LAI expresses interrelation of vegetation crown with optical radiation of the Sun and is very significant parameter for determinatio of of exchange ofСО , H O, and energy between vegetation and atmosphere. LAI is also the quantitative parameter of seasonal 2 2 changes of crown and phenology of vegetation which are admitted as integrated parameters of vegetation reactions on climatic changes. This index quantitatively can be determined both by methods of on-board measurements and methods of ground validation measurements. At the same time, the information derived by help of reflected from vegetation radiation depends on such parameters as the angle of solar elevation, background reflections, intrinsic special parameters of phytomass, and LAI index. The article examines the effect of sky background radiation on a value of the suggested modified index LAI. The carried out model researches showed that non-certainty of the suggested modified leaf area index (MLAI) was minimal upon decreasing type of function of dependence of FAPAR on sky background radiation i.e. upon big zenith angles of the Sun. On the basis of this fact the conclusion was made that the newly suggested index MLAI is most stable upon big zenith angles of the Sun, thus upon presence of data on sky background radiation leaf area index should be calculated using the newly suggested MLAI upon big zenith angles of the Sun.

Currently, the indices used to estimate the degree of salinity of the soil, calculated as the ratio of samples in the visible and infrared regions, are more informative than the indices based on measurements in the one spectral zone. The normalized difference index of salinity calculated on the Landsat OLI database has a fairly strong correlation with the electrical conductivity of the soil. Extreme combined indices are of some interest for the validation of the results of on-board measurements of soil salinity, where the possibility of automating the search for the extremum of such combined indices allows for the validation of the results of on-board estimates of soil salinity. The purpose of this work is (a) to study the possibility of developing a new, essentially extreme spectral composite index for assessing the salinity of land plots, where the first component of this index is calculated from the well-known model of on-board measurements, and the second from the results of ground measurements: (b) to study the possibility of using the proposed extreme index to validate the results of remote sensing of soil salinity. The article presents the theoretical foundations of the proposed new multicriteria method for validating the results of on-board measurements. The extreme property of scalar convolution of the multi-criteria optimization method, which is a weighted linear combination of partial criteria, is used as a basis. To validate on-board data, the sign of the appearance of an extremum in the target functional is used when using the results of ground and on- board measurements separately as a general argument. In this case, the measurements are carried out on the test site, where there is a gradient of soil salinity in geometric coordinates. The coincidence of the geometric locations of the occurrence of extremes in two cases indicates a positive result of the validation.

Ground-based measurements of atmospheric aerosol are mainly carried out using solar photometers. The results obtained with the help of these meters allow us to study the effect of aerosol on the amount of optical radiation entering the Earth’s surface, to create physical and chemical models of the atmosphere, to validate satellite data and to carry out atmospheric correction of these data. When measuring direct solar radiation, the photometer input also receives an optical signal of the “forward scattering” type. If the atmosphere is sufficiently polluted with aerosol and the zenith angle of the Sun is sufficiently large, the error in measuring the optical density of the aerosol can reach a significant value. Taking into account the above results of well-known experimental studies, it is relevant to develop a methodology for optimal aerosol measurements during the sunny hours of the day when the zenith angle of the Sun changes within large limits. The article is devoted to the optimization of daytime solar-photometric measurements of the optical density of atmospheric aerosol. On the one hand, an increase in AOD leads to an increase in forward scattering radiation and on the other hand, with an increase in AOD, there is a decrease in direct solar radiation, which in turn leads to a decrease in forward scattering radiation. As a result, the forward-scattered radiation has a maximum of AOD, which depends on the wavelength. Based on the results of known experimental studies of the measurement error of AOD, which occurs due to the influence of the scattering of solar radiation by aerosol particles in the forward direction, the problem of optimizing a series of such measurements is formulated. As a result of solving this problem, the functional dependence of the ratio of direct and diffuse radiation on the cosine of the zenith angle is obtained, at which the average value of the AOD measurement error reaches the minimum value. The mathematical solution of this problem is given.

The effect of a mixture of organic xenobiotics (nitrobenzene, ethylbenzene, aniline, xylene and styrene) was studied under biotesting conditions. Xenobiotics were toxic for Ceratophyllum demersum, Elodea canadensis, Chara fragilis, Callitriche palustris. The aim of the work was to assess the risk of complex pollution of water bodies by organic pollutants. Each substance was in microcosms at a concentration of 3 MPC. The incubation lasted 14 days. Macrophytes C. palustris and C. fragilis are highly sensitive test objects and are suitable for bioindication. E. canadensis demonstrated a high tolerance to pollutants and can be used for phytoremediation. Shoots of C. demersum showed moderate tolerance to contamination. This research is of an applied nature in environmental science. The relative limits of the tolerance range of macrophytes to mixed pollution with organic xenobiotics were identied. The data obtained supplement and expand the understanding of the pollution of aquatic ecosystems with organic solvents. The results of the experiments have revealed bioeffects in aquatic plants when aquatic ecosystems are polluted with organic xenobiotics. The article is of interest to researchers in the eld of ecology, ecotoxicology, hydrochemistry, hydrobiology, various sciences about the environment and the biosphere.

The article examines the modern lemnoecological state of the unique Lake Sugger, village of Bordon, Nyurbinsky District. Studies were carried out in order to obtain new limnological parameters for a scientifically based assessment of the modern ecological state, to determine the functioning of the lake ecosystem under the influence of anthropogenic effects. The research work of the Lake Science Laboratory is based on geoecological, geological-geomorphological and limnological methods and approaches to the study of lake ecosystems in Russia and the organization of their monitoring, developed and used in specialized academic institutes of the Russian Federation performing scientific research on large lakes. During the study, the modern morphometric parameters of the lake were determined, which is characterized by 2 its unique indicators: length - 6.443 km, maximum width - 4.934 km, water mirror area - 24.84 km , catchment 2 3 area - 188 km , water volume - 30.11 million m . It was revealed that the water balance of the analysed flow lake is determined by the presence of 17 inflowing tributaries and an outflowing one. In addition, atmospheric precipitation and seasonally melting water are involved in feeding the lake. Chemical analyses were carried out, during which the component composition of water samples was determined. The total mineralization does not exceed 246 mg/l and is characterized by a mixed type of water. Water contamination with organic substances, metal salts, fluorides and petroleum products was detected. The water of the lake has quality class 7 and is characterized as “extremely dirty.” The bottom sediments of the lake are represented by low-power clay sludge. It was revealed that according to geochemical and agrochemical indicators, deposits of the lake differ significantly from lake deposits of the lowland cryolithozone of Central Yakutia. The low chemical values of sludge indicate the slowness of the processes of mineralization of substances in cold water and the constant movement of the lake water.

Due to its geographical location in Central Yakutia, the uniqueness of the landscapes, the rich history of settlement and development of the territory,Amginsky District attracts an increasing number of tourists every year. The relevance of the article is in the increased interest in Amginsky District in the field of tourism and the lack of knowledge of its historical and cultural potential. The purpose of the article was to study the objects of historical and cultural heritage in Amginsky District and assess its potential for tourism development. On the basis of the objects of historical and cultural heritage identified on the territory of Amginsky District, a database was created. It includes information about 97 objects. 61 objects were retrieved from the List of cultural heritage objects of the Department of the SakhaRepublic (Yakutia) for the Protection of Cultural Heritage Sites. 36 objects were identified on the basis of a study of local history literature and official websites of municipalities. Based on the attribute information, maps of the placement of historical and cultural heritage objects on the territory of Amginsky District were compiled, and a map of the assessment of the historical and cultural potential of the ulus was created. The results presented in the article can be used by various tourist organizations for the development of tourist routes and excursions of historical and cultural thematic in the Amginsky district (ulus)

Event tourism has become widespread all over the world, including Russia and Yakutia, in particular. In the regions of Russia, many different types of event tourism are developing, but they are distributed unevenly across the country. The purpose of event tourism is to organize events that are timed to any event, have national, international historical, ethnographic, socio-economic characteristics of the regions and have an attraction for tourist visits.Event tourism in the regions of Siberia and the Russian Far East develops depending on the time, venue, scale, ideological orientation of the event, the main audience, the types of arts and thematic events. The multinational nature of the regions of Siberia and the Russian Far East contributes to the development of thematic national types of event tourism. As a result of the analysis of events of event tourism in the regions of Siberia and the Russian Far East, it was revealed that almost all types of event tourism at the international, regional and national levels are widespread. Yet there is a contradiction: there is a wide variety of types of event tourism, but they are not systematized by region. The problem is that there is no typology of types of event tourism in the regions of Siberia and the Russian Far East. The solution of this problem of systematization and research of the spatial distribution of event tourism in the regions has become the relevance of this article