"At the modern stage of the development of Geosciences, the study of hydrothermodynamic and ecological processes occurring in the natural environment (sea, atmosphere, soil), their monitoring and forecasting become very relevant and are a necessary condition for sustainable development of society. The Caucasus region is one of the most difficult regions of the world from the point of view its physical and geographical features. These features include the Black and Caspian Seas and the complex terrain of the Caucasus. The Seas and the atmosphere are unified hydrodynamic systems, between subsystems of which processes of an exchange of energies, momentum and substances continuously take place. One of the most effective ways to study natural and environmental processes is methods of mathematical modeling, which allows reproducing these processes and phenomena and studying the quantitative contribution of various factors to the development of such processes. The purpose of the paper is to discuss the models of the Black Sea and atmospheric dynamics developed at M. Nodia Institute of Geophysics of I. Javakhishvili Tbilisi State University, and some results of their implementation. The model of the Black Sea dynamics is based on a full system of ocean hydro-thermodynamics equations. Its high-resolution version, which is nested in the basin-scale model of the Black Sea dynamics of Marine Hydrophysical Institute (MHI, Sevastopol), is used to forecast main hydrophysical fields for the easternmost part of the Black Sea. The model of the atmospheric dynamics is based on a full system of atmospheric hydro-thermodynamics equations in hydrostatic approximation written in the terrain-following coordinate system and is realized for the extended territory including the eastern part of the Mediterranean Sea and Black and Caspian seas and for the Caucasus region. These models, after some modification will form the basis of the coupled Black Sea-atmosphere limited-area modeling system."
Microscale processes of dust distribution in the city of Tbilisi with a very complex topography are modeled using a 3D regional model of atmospheric processes and numerical integration of the transport-diffusion equation of the impurity. The Terrain-following coordinate system is used to take into account the influence of a very complex relief on the process of atmospheric pollution. Modeling is carried out using horizontal grid steps of 300 m and 400 m along latitude and longitude, respectively. The cases of the stationary background eastern and western weak winds are considered. In the model, motor transport is considered as a nonstationary source of pollution from which dust is emitted into the atmosphere. Modelling of dust micro-scale diffusion process showed that the city air pollution depends on spatial distribution of the main sources of city pollution, i.e. on vehicle traffic intensity, as well as on spatial distribution of highways, and micro-orography of city and surrounding territories. It is shown that the dust pollution level in the surface layer of the atmosphere is minimal at 6 a.m. Ground-level concentration rapidly grows with increase of vehicle traffic intensity and by 12 a.m. reaches maximum allowable concentration (MAC = 0.5 mg/m3) in the vicinity of central city mains. From 12 a.m. to 9 p.m. maximum dust concentration values are within the limits of 0.9-1.2 MAC. In the mentioned time interval formation of the highly dusty zones, and slow growth of their areas and value of ground-level concentrations take place. These zones are located in both central and peripheral parts of the city. Their disposition and area sizes depend on spatial distribution of local wind generated under action of complex terrain, as well as on the processes of turbulent and advective dust transfer. From 9 to 12 p.m. reduction of dust pollution and ground-level concentration takes place. After the midnight city dust pollution process continues quasi-periodically. As result of the analysis of vertical distribution of dust concentration is obtained that a basic dust mass emitted into the atmosphere is located in the 100 m surface layer. Concentration value in the upper part of this layer reaches 0.8 MAC and rapidly decreases with altitude increase.
With a baroclinic prognostic model of sea dynamics, the annual cycle of the Black Sea hydrological regime is modeled for constantly changing atmospheric circulation types characteristic of the Black Sea. Emphasis is placed on the hydrological structure of the upper sea layer in two extreme meteorological situations, storm and near-calm conditions over the sea basin. A significant difference is found in the character of the sea currents, and the main sea circulation features are determined for such situations. The system of model equations is solved using a method of two-cycle splitting on a grid with a 5-km horizontal step and 32 levels in the vertical.Wind is one of the main factors forming systems of currents in the seas and oceans. Therefore, the hydrological structure in water basins is largely determined by meteorological regimes over them. The multiyear meteorological observations over the Black Sea show that atmospheric processes over the sea have large variability and diversity of circulation regimes [1,16]. Wind stress is the main external factor exciting drift currents. It forms a specific Black Sea circulation regime under conditions of Earth's rotation together with internal factors, such as baroclinity, coasline, and bottom relief.One of the most important goals of the Black Sea oceanography is to study the Black Sea circulation processes in close connection with the atmospheric circulation and to obtain quantitative circulation characteristics of the sea. It cannot be solved using experimental methods only.The goal of this paper is a numerical study of the Black Sea hydrological structure in storm and nearcalm conditions representing two extreme atmospheric states in a wide range of circulation regimes developing over the Black Sea. Such meteorological situations are not rare over the Black Sea. Therefore, the study of the main features of the sea currents in these extreme situations is of special interest. Besides, some features of the circulation of the Black Sea waters in storm and calm conditions can be observed in intermediate meteorological situations.The annual cycle of the Black Sea hydrological regime was modeled using a baroclinic model of the sea dynamics [6, 7, 18] with continuously changing atmospheric circulation processes typical of the Black Sea basin. The proposed model is an improved version of the model of Black Sea dynamics developed earlier [5,8,[12][13][14]. It is based on the full system of the ocean hydrothermodynamic equations in a hydrostatic approximation. The system of equations is written in the Cartesian rectangular coordinate system for deviations of thermodynamic values (temperature, pressure, and density) from the standard vertical distributions. The empirical Mamaev formula [10] is used as the equation of state of seawater. Unlike [5,8,[12][13][14], the model considers water exchange between the Black Sea and the Sea of Marmara through the Bosporus, the Danube runoff, absorption of total solar radiation in the upper sea layer, spatial and temporal variation of the c...
The distribution of PM2.5 in the atmosphere of the city of Rustavi and its environs was studied under eastern background light air, gentle and fresh breeze. It has been established that the maximum concentrations of PM2.5 in the atmosphere of Rustavi are almost always higher than the corresponding maximum allowable concentrations. The trend of hourly changes in concentrations showed that during the day the concentration of microparticles reaches its maximum in the various period of the day. Numerical modeling of the local distribution of microparticles carried out in the city of Rustavi during background easterly light air, gentle and fresh breeze showed us that the change in the daily regime of relief and temperature with eastern light air in Rustavi for 12 hours leads to a complex and significant change in the wind speed directed to land. It forms on the territory of Kvemo Kartli the opposite current of the background wind, which corresponds to the horizontal circular wind circulation. The value of circulation gradually decreases with increasing height and in the boundary layer of the atmosphere (600 m above the earth's surface) has the form of a wave disturbance. the picture obtained with an average background east wind is qualitatively similar to the field obtained with a background light air, and with a fresh breeze, in contrast to the case of a light air and gentle breeze, the pollution zone covers most of the simulation zone.
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