Why is it formed in big cities? Why new cities were created in Russia in the 20th century. The emergence of small towns in the wake of centripetal processes in settlement. The era of satellite cities
If you ask “where do you live,” more than half of people will answer - in such and such a city, with such and such a population. Only a few can boast that they live in a town or village.
Big city waste
Classification of cities by population
In accordance with the classification adopted in Russia, urban settlements with a population of over one million are classified as to the largest cities, with a population of 250–1000 thousand people – to large, with a population of 100–250 thousand people – to big ones, 50–100 thousand – to average, 20–50 thousand – to the small ones. Currently in Russia there are about a thousand cities and more than two thousand urban-type settlements, in which approximately 70% of the country's population lives.
St. Petersburg is one of the largest cities in Russia
Over the past 50 years, the share of Russia's urban population has increased from 52 to 73%. Large, large and largest cities (hereinafter referred to as large for brevity) differ from medium and small cities in a number of ways:
– territories occupied by various buildings;
– intensity of its development;
– anthropogenic pressure on the occupied territory;
– destruction of natural ecosystems;
– the formation of a specific urban ecosystem, significantly different from the natural ecosystem.
Under ecosystem we understand a biological system, which includes living organisms, their habitat and a system of connections that ensures the exchange of matter and energy between them. Urban ecosystem is an artificially created and human-maintained environment. This includes cities and urban-type settlements.
Problems of life in big cities
The general trend in the development and growth of cities is the progressive deterioration of living conditions in them. One of the greatest tragedies of cities is that they, being the materialized level of development of civilization, become not only inconvenient, but also significantly dangerous for life.
In millionaire cities, the population cannot reproduce itself; they are characterized by a predominance of elderly citizens. Population growth occurs due to mechanical growth: migration from rural areas and small towns, as well as from former Soviet republics and foreign countries.
Urban population increases due to illegal migrants
Such ugly phenomena as the growth of crime, drug addiction, and alcoholism flourish in cities. Cities are often compared to demographic “black holes”, “monsters devouring the human race”, and the death of large cities is predicted. However, the experience of mankind shows that there is no alternative to the city.
Drug addiction and alcoholism are companions of big cities
It is clear that life in rural areas is generally healthier than in the city. Nevertheless, the “average” Russian has no desire to move to the countryside, although he is not averse to going to his dacha on weekends.
In Western countries with an excellently developed road and information infrastructure, as well as the availability of personal vehicles, the outflow of the middle class from cities to the suburbs has been replaced by a return to the cities.
Why are cities attractive to live in?
The vitality of the city is explained by the fact that this type of settlement best satisfies the basic needs of people.
– it’s comfortable to live in the city, since everything new and progressive appears here first;
– it is easier to get higher education;
– it’s easier to find a job you like in the city;
– the city is an incubator for creative activities that shape new directions in science, production, art, and culture.
Cities reflect the history of the development of civilization. A variety of production and service industries are concentrated in large cities; their developed infrastructure contributes to the modernization of old and the development of new industries and jobs. The diversity and high concentration of places of employment, as well as ways of spending leisure time, “outweigh” the environmental shortcomings of cities in the eyes of residents.
In a big city there is always something to do during your leisure time.
Urbanization- a progressive phenomenon. Whether we like it or not, cities and industrial zones exist and will continue to develop for a long time. It is no coincidence that the World Health Organization (WHO) several years ago organized the International Scientific Center for Development in the Japanese city of Kobe and included the problems of urbanization and the study of the current situation in the largest cities of the world among its main areas of activity.
In many cities around the world, the population already exceeds 250 thousand people. These cities have already become largely isolated from the surrounding natural environment, both due to the large territories they occupy and due to the large energy load on the environment.
A special place in relation to environmental load is occupied by industrial zones, where, as a rule, large energy capacities and intensive industrial production are concentrated.
The city is a powerful source of pollution
First of all, megacities pollute the atmosphere. In recent years, this process has become especially noticeable. To main sources urban air pollution include exhaust gases from automobiles and emissions from industrial enterprises. Along with the air it becomes polluted soil and water. In many cities, drinking tap water is life-threatening.
Once I was invited to a television program where the quality of various water filters was assessed. All experts were given a taste of water from the St. Petersburg water supply, and then after purification with various filters. It turned out that to determine the quality of tap water, you only need to smell it...
"Tasting" of St. Petersburg tap and filtered water. On the left is the author of the article.
One of the big problems of cities is recycling of solid industrial and household waste. Modern waste processing technologies are not available everywhere, and standard types of waste incineration plants cannot cope with the growing volume of waste.
The problems mentioned are not insoluble. In Japan, Germany and the USA, a lot of work is being done to improve the environmental situation in large cities. For example, walking along the streets of Tucson (a city with a million people), located in Arizona, USA, even during rush hours, you will not smell gasoline, since the country has strict requirements for the quality of vehicle emissions.
Probably, if you really want, you can turn the city into an urban oasis, convenient and safe for life.
The weather features of individual areas, for which the observations of one meteorological station are sufficient to characterize, are called local climate.
The local climate is determined by atmospheric air currents; it is influenced by the terrain features of the territory and the nature of the surface (breezes, mountain-valley winds); it can be determined by the local influence of the earth's surface on atmospheric currents (hair dryer, boron); it is also formed as a result of human activity (urban climates).
Along the coasts of seas and large lakes there are winds that change their direction during the day. These are the breezes. During the day the sea breeze blows from the sea to the shore, at night the coastal breeze blows from the shore to the sea. During the day, land warms up more than water, and the air above it is warmer and lighter. Cold, heavy air from the sea begins to displace less dense air over land, and the heat of the day begins. At night, the land surface cools faster. The air above it, cooling, begins to push out the air above the water. A night breeze forms.
In the warm season, the breeze captures a layer of air up to 1 km. You can feel it by visiting the shores of the Black, Azov, and Caspian seas on the island of Cuba, as well as on the shores of other seas of low latitudes. The daytime breeze blowing from the sea brings coolness to the highly heated land and increases humidity. In Madras (India), a sea breeze lowers the air temperature by 2 - 8 C and increases humidity by 10 - 20%, and in West Africa the breeze reduces the temperature by even 10 C.
Mountain-valley winds
Similar daily wind changes often occur in the mountains. During the daytime it blows upward from the valley to the mountain slopes. At night, the direction of the wind changes, and the air already tends downwards - along the mountain slopes to the valley.
The cause of mountain-valley winds is the same as that of breezes. During the day, warm air above the highly heated slopes begins to rise, carrying the valley air with it. And at night, on the contrary, the slopes cool down, and the cold air around them begins to flow down.
Mountain-valley winds are clearly visible in the summer in the Alps, the Caucasus and Pamirs, and in other mountainous regions of low latitudes. Wind speed can reach 10 m/s.
In the mountains, “fen” are often observed - warm, dry, gusty winds that sometimes blow from the mountains to the valleys (in America, such a wind is called “Chinook”). They increase the air temperature in mountain valleys and can greatly dry out the soil and plants.
In May 1935, in the northern foothills of the Caucasus, a southern foehn from the Armenian Highlands increased the air temperature in Nalchik to +32 C. In the USA, in the state of Montana, the temperature in December once rose from - 40 to + 4.
An intense and prolonged hair dryer leads to strong melting (even evaporation) of snow, increases the water level in rivers and can cause floods.
Hair dryers are a common occurrence in the Alps and the Caucasus, they hit the southern coast of Crimea like a wall, and are also found in the Altai mountains, Central Asia, Yakutia and western Greenland.
In some areas where low mountain ranges approach the sea coast, a strong cold wind - bora - sometimes reaches hurricane force, and its speed is 20 m/s. Falling onto the coast through low mountain passes, it causes strong waves at sea and is capable of lowering the air temperature by 20 C. Bora is observed on the Black Sea in the region of Novorossiysk, on Novaya Zemlya (and the wind speed here can reach 70 - 80 m/s), on the Adriatic coast of Yugoslavia. In some areas, such winds have local names: nord - in the Baku region, mistral - on the Mediterranean coast of France, sarma - on Lake Baikal.
The city is an island of heat
Within large cities, special local climatic conditions are formed. This is due to the fact that the city’s territory always warms up more than its surroundings. And therefore it is customary to say that the city is an island of heat. Thus, in London the average annual air temperature is + 12.5 C, and in rural areas - +9.5 C. On the outskirts of the city, a local atmospheric front with strong winds arises.
Interestingly, cities also have a breeze, which is called "urban". It appears in calm and hot weather, when a colder wind from the suburbs blows along the streets towards the city center.
The climatic features of large cities include smog - the accumulation of toxic smoke and gas near the earth's surface. Smog hangs over the city like a dirty, foggy cloud, bringing illness and even death.
“The February series of seminars, held by the Laboratory of Market Theory and Spatial Economics, will bring together very experienced specialists for an in-depth discussion of narrowly focused issues. These kinds of meetings are very productive. Unlike large congresses, where no more than 20 minutes are allocated to each speaker, at the workshop there is the opportunity to make detailed hour-long reports, and the topics are selected more narrowly - for people conducting research in related fields of science, so the communication is deeper.
The theoretical issues that are planned to be discussed concern international trade and agglomerations. For example, why is economic activity concentrated in certain regions, cities, and countries? How does this happen? The basic working idea is that the agglomeration effect is associated with “increasing returns to scale.” In particular, fixed investments in creating and maintaining a company pay off from replication, better in a large market than in a small one. Firms are more willing to form in large cities, create jobs, those who want to get hired go there, the city grows, and so on in the same spirit. Supply and demand go to demand. In addition, firms need each other, have positive externalities, so they accumulate next to each other. This is how agglomerative, centripetal forces arise. But if they were not opposed by some centrifugal ones, then there would only be one city left in each country. In reality, the approximate pattern is often as follows: 1 largest city, 2 half smaller, 4 four times smaller, etc., this is called “Zipf’s law” (in Russia, however, the only city of the second level is St. Petersburg, and the cities of the third are Yekaterinburg, Novosibirsk, Nizhny Novgorod - noticeably less). Why is that? Why are big cities still growing while small towns are shrinking? By the way, this state of affairs is typical both for our country and for other states.
Let's say, in Russia, cities with a population of over a million and larger are growing, cities with a population of half a million have stagnated in size, and small towns are losing weight. This happens in countries similar to ours. But in Belgium and Holland, the agglomeration process unfolds differently. A country like this is so densely populated and the transport network is so developed that it can be considered one market, one city. In Holland with a population of 16 million, which occupies less space than the Leningrad region, cities do not need to enlarge, the population is continuous. Its entire territory is a sales market for any company. This is a different pattern of agglomeration.
Russia is still following the path of urban growth, and so is continental China. But its coastal part is developing as a densely populated area. Our task is to develop the theory of economic geography and try to apply it to practice, and the current meeting will touch on several special issues.
Listing by person, for example, Sergei Afontsev will talk about the effects of removing trade barriers within the framework of trade unions. He is a leading researcher at the Institute of World Economy and (MoE and Ministry of Defense of the Russian Academy of Sciences), a specialist in trade alliances and trade policy. Not so long ago the newspapers reported about a triple ?? growth in trade between Belarus and Russia, but if changes in gas policy and other similar factors are subtracted from this gigantic figure, then the net figures will not look so significant. And Sergei Afontsev is one of the few specialists who, with numbers in hand, is able to competently identify, using econometric techniques, the effects of reducing trade barriers on the overall volume of trade and on individual industries.
NES professor Natalya Volchkova works on similar topics. Perhaps she will develop the topic that she reported to us last time. These are econometric estimates of how significant the visa regime is among trade barriers. The visa itself is inexpensive, but the regime complicates the escort of goods abroad. It turned out that the visa regime can reduce the volume of trade between countries by several percent. Volchkova’s collaborator, Natalya Turdyeva from CEFIR, presented modifications of the “computable general equilibrium model” at the last report in the Laboratory. Similar models, created and combined with real figures over more than one year, exist in the USA, Australia and Europe. They serve to assess the consequences of major government decisions, such as joining the WTO, or Germany's abandonment of nuclear power. Forecasters predict smoother changes, as a rule, by extrapolation: what grows is predicted to grow, but with major shifts this is not possible, and I will not suggest anything other than CGE. Natalya works according to the methodology of the “European” model of Tarr and Rutherford, according to which scenario calculations were made for the entry into the WTO of Ukraine and then Russia. Today Natalya Turdyeva is a key specialist in Russia on CGE and will tell you how a multi-regional version of such a model works. Among the empiricists, our long-time Ukrainian colleagues Alexander Shepotila and Vladimir Vakhitov, who assessed Ukraine’s accession to the WTO, will come to us, and today they are working on assessing the effects of foreign trade and interregional ties in Ukraine.
In the theoretical block of reports, Christian Behrens will talk about his model of urbanization with his co-authors: how a system of cities arises in a country, say, the above-mentioned Zipf’s law, and what holds back agglomeration. As we said, excessive crowding of people and economic activity, overcrowding of cities are opposed by certain dispersion forces. This is, first of all, the high cost of land (and therefore buildings) and the congestion of the transport network - they are felt in St. Petersburg and very strongly felt in Moscow. Therefore, those industries that are not very sensitive to the forces of “gravity” are removed from the city. Today, most industrial sectors have long been located in the suburbs, outside the city. It is inappropriate to maintain material production in a city, and cities have turned into clusters of offices, medicine, education, and in general are turning into producers of exclusively information products.
Behrens's work is interesting in that he included in his consideration all the main elements discussed: the price of land, the cost of transport in the city, the economic equilibrium between consumers and firms, the migration of both. Moreover, he was able to calibrate all the important patterns and factors, both agglomerating and dispersing. This means using real data to evaluate the strength of patterns—this is new in the theory of urban agglomeration. And in the theory of general equilibrium at the regional level, we will also sooner or later reach calibration and evaluate how strong the patterns are. It is an intellectual challenge for economists to learn how to make quantitative forecasts. Let's say - to predict whether the population of Russia will continue to grow, move from the Urals to the European part, or stop.
In this area, Tatyana Mikhailova taught us about the economic history of Russia and the determinants of population distribution. Now she will talk about a new study commissioned by Russian Railways, an empirical assessment of Russian railway bottlenecks, and how debottlenecking can benefit economic growth. Bottlenecks are those junction stations where the flow of wagons and goods is slowed down. She is also now engaged in forecasting suburban passenger traffic in Moscow, since there is a project for the development of suburban electric trains, which can be sufficiently taken over by the passenger traffic of the outskirts.
Vera Ivanova and Evgenia Kolomak will present their empirical research on the convergence of Russian regions. They explore the question: are Russian regions converging in economic indicators, and what factors influence the convergence? In fact, this project is an empirical survey of regions with an attempt to calculate correlations between regional indicators and identify factors influencing the increase in economic activity and productivity of regions. In a general sense, all our studies serve as attempts at long-term forecasting. I would like to understand how our and the world economy will develop in the next 10, 20, 30 years.”
Prepared by Tatyana Chernova, Maria Zharkova. National Research University Higher School of Economics - St. Petersburg.
Special microclimatic conditions are formed in the city. Microclimate of the city– this is the climate of the ground layer of air in individual areas of the urban area. The ground layer of air occupies an air space two meters above ground level.
The formation of the city's microclimate, in addition to natural conditions, is influenced by the conditions created by urban development, as well as the functioning of vehicles, thermal power plants, industrial and other enterprises. Urban development changes the natural topography: it increases the roughness of the underlying surface (for example, it creates basin conditions against the background of a flat topography), includes many vertical surfaces, and creates rough terrain. In addition, the thermophysical properties (heat capacity and reflectivity) of elements of urban development (walls of buildings, roofs, roads, pavements) differ from the thermophysical properties of elements of the natural environment. The city's soil is hidden under buildings and road (asphalt) surfaces. Under natural conditions, part of the moisture goes into the soil. In the city, a significant part of the precipitation does not fall into it. Urban wastewater is discharged into storm drains or city sewers. During the operation of vehicles, heating the city, and the functioning of enterprises, heat flows enter the atmospheric air, gaseous pollutants, liquid and solid suspended particles are emitted.
The listed features of the urban area determine the formation factors of the city microclimate:
· changes in relief due to urban development;
· differences in the thermophysical properties of the surfaces of urban development elements and the natural environment;
· differences in the albedo of the underlying surfaces of the city and its surroundings;
· artificial heat flows;
· air pollution;
· reduced evaporation due to asphalt pavements and regulation of precipitation runoff;
· a sharp decrease in surface area with vegetation and natural soil, etc.
These factors influence the city's microclimate simultaneously, but their contribution at different times of the year and in different climatic conditions is very different. They cause changes in the natural radiation balance, conditions of heat and mass transfer, and disruption of the natural moisture cycle. All this determines the microclimatic variability of general climatic regimes in certain areas of a large city.
Radiation regime of the city microclimate . Due to atmospheric air pollution with solid and liquid suspended particles (aerosols), its transparency decreases. Therefore, part of the solar radiation does not penetrate into the city. Depending on the degree of air pollution, time of year and day, a decrease in its intensity of up to 20% is observed.
In urban planning, direct solar radiation plays a decisive role, which is assessed by the insolation regime. Insolation mode– mode of exposure of urban areas and building premises to direct sunlight. Insolation of urban areas is reduced by cloudiness and air pollution. Solar exposure is essential for life. It has a healing and positive psychological effect on a person. The duration of insolation is regulated by sanitary standards and relevant paragraphs of SNiP. Insolation standards depend on the climatic zone of the urban area. In accordance with SanPiN 2.2.1/2.1.1.1076-01 in the territories of playgrounds, sports grounds of residential buildings, group playgrounds of preschool institutions, sports areas, recreation areas of secondary schools and boarding schools; recreation areas of inpatient medical institutions, the duration of insolation should be at least 3 hours for 50% of the site area, regardless of geographic latitude.
SanPiN also defines hygienic requirements to limit the excessive thermal effects of insolation. In residential areas of the III and IV climatic regions, protection from overheating must be provided for at least half of the playgrounds, places where play and sports equipment and devices are located, and recreational areas for the population.
Temperature regime of the city microclimate . The air temperature in a large city is 1...4 degrees higher compared to its surroundings, sometimes this difference reaches 8 degrees.
The increase in temperature is explained by the heating of building elements due to their absorption of solar radiation and the reflection of radiation by urban surfaces, as well as a decrease in the effective radiation of heat over the city. The amount of reflected radiation depends on the slope and orientation of surfaces, as well as the albedo of building and road materials. In this case, mutual irradiation of building elements may occur, and near the insolated surfaces of the urban environment, the air temperature may increase significantly. Due to atmospheric air pollution, as well as inhomogeneities of the underlying surface caused by buildings, the effective radiation over the city is weakened and its night cooling is correspondingly reduced. In addition, significantly less energy is spent evaporating moisture from asphalt and other urban surfaces compared to the energy required to evaporate moisture from vegetation. Therefore, in the ground layer of air in an urban area, due to the low energy consumption for moisture evaporation, much more heat remains in comparison with the surrounding area.
Additional heat enters the atmospheric air when fuel is burned. Thermal emissions from vehicles, industrial and energy enterprises can cause a local increase in air temperature over certain areas of the urban area - a transport highway, an industrial zone, a thermal power plant. Thus, according to space monitoring data (recording of infrared radiation), thermal anomalies occupy a quarter of the territory of Moscow (March 1997).
An increase in air temperature inside the city compared to the temperature of the surrounding area leads to the formation of a so-called “heat island” over the city - an area of high air temperature, which has the shape of a dome. The size of the “heat island” and its other indicators depend on meteorological conditions and the characteristics of the city. The “heat island” is destroyed by wind or other precipitation, but is stable in calm conditions. At an altitude of up to several hundred meters, masses of warm and cold air circulate along the borders of the “island”. The vertical speed of air flows is relatively low. For example, on an “island” with a diameter of 10 km and a wind speed of 1 m/s in a layer 500 m thick, it is about 10 cm/s. In the “heat island” the atmospheric air pressure is low. This helps attract clouds from the upper atmosphere. Therefore, clouds over the city are located much lower than over open areas. Rising air currents form cumulus clouds. The formation of a “heat island” causes a decrease in the influx of solar radiation into the territory of a large city, an increase in the amount of precipitation, and an increase in the frequency of fogs.
Wind regime of the city microclimate . Elements of urban development and green spaces change wind speed and direction. Usually the wind speed in the city is lower than outside it. Increased wind is possible when the city is located on hills or when the wind direction coincides with the direction of the streets. For cities where wind speeds are insignificant, local air circulation is typical. The reason for their occurrence may be different temperatures or illumination of certain areas of the urban area. Air movement, called thermal ventilation, occurs between the city and its surroundings, between green areas and built-up areas, between the sun-heated and shaded parts of the streets. The presence of bodies of water contributes to the formation of local circulation, similar to breezes. Air moves from bodies of water to buildings.
The wind regime of the surface layer of air in urban areas is usually called aeration regime. The aeration regime is considered comfortable if the wind speeds in the building area are in the range from 1 to 5 m/s. Areas of the urban area where the wind speed is less than 1 m/s are classified as unventilated, and areas of more than 5 m/s are classified as blowing zones. The training manual separately identifies a comfortable aeration mode (wind speed from 1 to 3 m/s) and an aeration mode close to comfortable (wind speed from 3 to 5 m/s). Unventilated areas of urban areas, or areas of stagnant air, create an unsanitary condition. Blowing zones are uncomfortable for humans.
Humidity regime of the city microclimate. Air humidity in large cities is lower compared to surrounding areas. This is due to increased atmospheric temperatures and lower moisture content due to a decrease in the amount of evaporation. The greatest difference in air humidity between the city and its surroundings throughout the year is observed in the summer, and during the day - in the evening hours. In winter, the city's air can be more humidified due to steam emissions from man-made sources. The city receives less snow in winter and more rain in summer.
The formation of cloudiness in the city at high humidity is facilitated by increased convective instability and air pollution. The formation of clouds with insufficient humidity is also facilitated by convective currents over the city. They prevent the horizontal movement of air masses coming from the windward side and draw them into the upward air flow. As a result, clouds form and precipitation occurs.
With significant air pollution and weakening wind speeds, there may be more fog in the city. As the temperature rises and the relative humidity drops, there is less fog in the city than outside it.
Bioclimatic conditions of the city territory. Weather conditions can have a negative impact on a person’s well-being and can cause a feeling of comfort. Weather is the state of the atmosphere in a given place at a certain moment or for a limited period of time (day, month). Weather is caused by physical processes that occur during the interaction of the atmosphere with space and the earth's surface. Weather is characterized by meteorological indicators: atmospheric pressure, temperature and humidity, wind speed and direction.
Specialists in medical climatology have developed a number of bioclimatic indicators for human perception of weather conditions. These indicators were obtained on the basis of parallel physiological and meteorological observations. The most widely used indicators reflect the thermal state of a person.
The thermal state of a person is determined by his physiological indicators, physical activity, heat-protective properties of clothing, but primarily by a complex of meteorological factors: air temperature and humidity, solar radiation and wind speed. It has been established that a person experiences thermal comfort when his thermoregulatory system is in a state of least tension. Thus, low air temperature causes a feeling of cold discomfort, which increases with increasing wind speed and increasing humidity. In hot climates, when the air temperature is close to or above body temperature, even the wind does not always bring a feeling of freshness. The combination of high temperature and high humidity causes stuffiness.
Bioclimatic indicators that reflect the thermal state of a person include: equivalent effective temperature, heat load on the human body, physiological type of weather, etc. Based on these indicators, methods for assessing the bioclimatic conditions of a territory have been developed. Let's consider the method of temperature scales, the method of heat balance of the human body and methods based on the classification of weather types.
Temperature scale method. There are mainly two types of temperature scales used: equivalent effective temperatures (EET) and radiation equivalent effective temperatures (REET). EET takes into account the complex effects of temperature, air humidity and wind speed on a person’s thermal sensation. REET additionally takes into account solar radiation. The complex effect on a person of air temperature, wind speed and relative humidity causes a heat sensation effect that corresponds to the effect of stationary air completely saturated with moisture at a certain temperature, called equivalent effective temperature. To assess the bioclimate of cities located in different climatic regions, the following recommendations are given on the use of a system of temperature scales. The EET interval is taken as a comfort zone:
· for southern cities – 17...21 0 C;
· for cities in the middle zone, Siberia and Primorye - 13.5...18 0 C.
EET below the specified limits characterize the state of cooling, and above - overheating. When calculating EET, in addition to average long-term indicators, daily meteorological data should be used. A person adapts to average climatic conditions. Extreme conditions (their frequency, intensity, duration) can cause a negative reaction in the body, especially in people with poor health.
Data on EET and REET make it possible to assess the bioclimatic resources of a particular city: determine the average duration of comfortable and uncomfortable periods during the year; calculate the frequency of weather conditions that provide the state of overheating, comfort and cooling, and consider the distribution of their degree of discomfort in abnormally hot and cold years (Fig. 3.1).
With the help of EET and REET, it is possible to determine the features of the formation of the bioclimate depending on the characteristics of the building, the heterogeneity of the relief, the presence of forests, the proximity of water bodies and, as a result, identify zones with varying degrees of comfort for living and recreation of citizens. The EET and REET methods can be used in any climatic regions and ensure comparability of results.
Method for calculating the heat balance of the human body is based on an equation expressing the equality of heat gains and heat losses:
R k + M = R q + P + LE + B,
Where Rk– arrival of short-wave radiation to the surface of the body, M– body heat production, Rq– long-wave radiation, R– convection, L.E.– heat consumption for sweat evaporation, L– latent heat of evaporation, E– the amount of moisture loss by sweat evaporation, IN– heat consumption for heating the exhaled air and saturating it with water vapor during evaporation from the surface of the lungs.
Rice. 3.1. Recurrence of comfortable and uncomfortable weather
by equivalent effective temperatures (Chita):
1) EET< 18,6 0 С (охлаждение); 2) ЭЭТ = 13,6 - 18 0 С (комфорт);
3) EET > 18 0 C (overheating)
This method is used to assess the bioclimate of cities with hot climates and is unsuitable for cities with temperate and cold climates. The amount of moisture loss through sweat evaporation is taken as an indicator of the degree of heat load on the human body in hot climates. An indicator of the intensity of the thermoregulatory system is also used, which is the ratio of the actual heat load to the maximum possible under the same meteorological conditions. The comfortable state of an adult (the body area is assumed to be 1.5 m2) corresponds to values of moisture loss by sweat evaporation of 50...150 g/h and values of the thermoregulatory system tension index of 5...12%. Clothing can reduce sweating by 33...45%.
Methods based on classification of weather types, consist in the fact that the bioclimatic characteristics of the territory are given according to the totality and sequence of frequency of weather types (methods of complex climatology). In turn, weather types are defined in the corresponding weather classifications.
Climatic weather classification is based on combining the entire variety of meteorological conditions of the warm and cold periods of the year into types and classes of weather. Each type (class) of weather is determined by strictly limited intervals of air temperature and humidity, wind speed and cloudiness (the latter is considered as an indirect indicator of the radiation regime). There are overheated, hot, warm, comfortable, cool, cold and harsh weather. A method for assessing bioclimate based on this classification allows one to obtain a background picture of the distribution of weather conditions in relation to the thermal state of a person. The method is visual, convenient and is often used for bioclimatic characterization of cities. At the same time, the method is not reliable enough to assess the bioclimate depending on the microclimatic characteristics of small areas.
Physiological classification of weather based on various types of human thermal state and the resulting thermoregulatory load. There are four classes of cold weather with varying degrees of overcooling (1X, 2X, 3X, 4X), four classes of warm weather with varying degrees of overheating (1T, 2T, 3T, 4T) and comfortable weather (H) (Table 3.2). The bioclimate assessment method, based on physiological classification, consists of taking into account the frequency of uncomfortable weather types (2X, 3X, 4X, 2T, 3T, 4T). The assessment results are expressed graphically in the form of climatograms.
Climatic-physiological classification is based on physiological types of weather and their meteorological characteristics (a combination of different values of air temperature, wind speed and total cloudiness) (Fig. 3.2, Table 3.3). The classification is intended for conditions with a relative humidity of 30...60%, optimal for humans. This weather classification is used to assess the recreational potential of suburban areas and its use for summer recreation.
All existing methods for assessing the influence of climate and weather on the human body cannot be considered universal. This is due, first of all, to the complexity of the objects under study - humans and the atmosphere, as well as to the different abilities of the human body to adapt to local climatic conditions and to the individual characteristics of a person (age, gender, health status, level of physical activity).
Dispersion of pollutants in atmospheric air affects the environmental situation in the city. Solid particles of pollutants larger than 0.1 mm in size settle onto the underlying surface under the influence of gravitational forces. Small, solid and liquid particles, as well as gaseous substances, spread in the atmospheric air due to diffusion.
Table 3.2
Weather types according to physiological (FC) and climatic-physiological classification (CPC)
Rice. 3.2. Rating scale for determining the degree of favorable weather for humans:
1 - cold, uncomfortable; 2 - cool subcomfortable; 3 - comfortable; 4 - hot subcomfortable; 5 - hot, uncomfortable; a) wind speed 0...0.2 m/s; b) 2.1… 4.0 m/s; c) 4.1… 6.0 m/s; T- air temperature, P- cloudy, Q- total radiation
The degree of dispersion of pollutants depends on meteorological conditions and is primarily determined by the wind regime and temperature stratification of the lower layer of the atmosphere. Meteorological conditions may contribute to:
· accumulation of pollutants during inversions, calms and fogs;
· decomposition of pollutants under favorable radiation conditions, temperature conditions and the presence of thunderstorms;
· removal of pollutants during strong winds and heavy rainfall.
That is, the scattering ability of the atmosphere (SCA) is determined by the characteristics of meteorological conditions. When assessing air pollution from emissions from vehicles and industrial enterprises, the concept “ air pollution potential"(PZA). PZA is a combination of meteorological conditions that determine the possible level of atmospheric pollution for given emissions of pollutants (see Table 3.3). The characteristic of atmospheric pollution potential is opposite to the dispersive capacity of the atmosphere: the higher the RSA, the lower the PZA.
Hazardous atmospheric phenomena. Phenomena dangerous to the city include temperature inversions and smog.
Temperature inversion create trapping layers of air. Surface inversions cause a lack of aeration in residential areas and thereby contribute to the accumulation of pollutants in the surface layer. Low, elevated inversions, like a “roof,” cover the city and prevent the dispersion of harmful impurities. Inversions in cities cause an increase in the concentration of pollutants in the air and contribute to the formation of an unfavorable environmental situation.
When temperature inversion occurs, building areas on hilly terrain are located above the upper boundary of the inversion layer, on the middle and upper parts of the slope or plateau. At the same time, areas located in a basin or valley are unsuitable for residential development.
Smog (from the English smoke - smoke and fog - fog) is a toxic fog. It occurs under unfavorable meteorological conditions and high concentrations of harmful substances in the ground layer of air. Smog phenomena were observed in different years in London, Los Angeles, New York, and Tokyo. There are three types of smog - reducing (London type smog), oxidative or photochemical smog, and ice type smog.
Reducing smog is typical for large industrial centers. It is an air mixture of soot particles and sulfur and nitrogen oxides. Oxides, when interacting with atmospheric water, form aerosols of sulfuric and nitric acids. Due to the irritating effect of acids on the bronchi and respiratory tract, smog has a negative effect on people's health. In 1952 and 1962 This type of smog caused the death of several thousand people in London.
Photochemical smog is observed in cities with high solar radiation intensity. It is formed by the interaction of sunlight with nitrogen oxides and hydrocarbons contained in vehicle exhaust gases and industrial emissions. Photochemical smog is a complex air mixture consisting of oxidants, mainly ozone, mixed with other oxidants, including tear gas - peroxyacetyl nitrate (PAN).
Initial reaction of smog formation:
NO 2 + hu ® NO + O.
Atomic oxygen interacts with oxygen O2 and inactive substance M (for example, nitrogen):
O + O 2 + M ® O 3 + M, NO + O 3 ® NO 2 + O 2 .
A special climate is formed in cities, which on hot summer days is close to the climate of a semi-desert or even a rocky desert. It’s not for nothing that cities are called stone deserts with green oases of squares, gardens and parks. In summer, the temperature on the asphalt surface reaches 45-55°C in the afternoon.
The temperature of the red brick wall is 41°.
White wall – 38°C.
And the lawn is 25°C.
All these differences are caused by the unequal absorption capacity of surfaces and the evaporation of moisture by plants (transpiration), which results in a decrease in air temperature.
On windless days, a temperature inversion layer can form above cities at an altitude of 100-150 m, which traps polluted air masses over the city territory. This, along with significant thermal emissions and intense heating of stone, brick and reinforced concrete structures, leads to heating of the central areas of the city. Trees and shrubs in the city center bloom 7-10 days earlier than on the outskirts.
As a result of thermal pollution, heat zones (islands) are formed over cities, over which a kind of local circulation of air masses is established, called urban breezes. On hot summer windless days, the air in the center heats up and rises, which leads to its inflow from the outskirts, both from forested areas and from industrial zones, regardless of their location in relation to the wind rose. If city breezes blow from the outskirts, they bring relatively clean air to the center. But such winds do not always appear. With a powerful anticyclone and high air pressure, city breezes may not occur.
Increased convection and technogenic dust in the air over the city leads to an increase in the frequency of thunderstorms and, in general, to an increase in the intensity and total amount of precipitation.
Dust emitted by air transport, industrial enterprises, and the thermal power complex sharply increases the content in the atmosphere of condensation nuclei (dust particles, sulfur and nitrogen compounds) absorbed by water droplets, forming aerosols. Therefore, there are more cloudy, cloudy days.
Due to smoke, dust and gas pollution, the city receives 15% less solar radiation, smog is observed 65% more often, and relativeI air humidity is 6%, wind speed is 25% less than in rural areas.
Throughout the world, in large cities, solar radiation has decreased by 10-30% over the last century. The intake of ultraviolet radiation has especially significantly decreased, which leads to an increase in the content of pathogenic bacteria in the air. This has a negative impact on the health of urban residents, because... with reduced insolation, the elimination of a number of toxic substances from the body, in particular heavy metals and their compounds, slows down, as well as the synthesis of important enzymes in the body.
The thermal regime of the soil in cities is non-standard. In the hot summer, asphalt pavements, heating up, give off heat not only to the ground layer of air, but also deep into the soil. At an air temperature of 26-27°C, the soil temperature at a depth of 20 cm reaches 34-37°C, and at a depth of 40 cm - 29-32°C. These are real hot horizons - exactly those in which the ends of the root system of plants are usually located. Therefore, the uppermost layers of urban soils contain practically no living roots. This creates an unusual thermal situation for outdoor plants; The temperature of underground plant organs is often higher than aboveground ones. Under normal natural conditions, the life processes of most plants in temperate latitudes occur with reverse temperature stratification.
In winter, due to the removal of fallen leaves in autumn and snow in winter, urban soils become very cold and freeze deeper. On city streets where snow is regularly removed and the asphalt layer has high thermal conductivity (i.e. the ability to lose heat), the soils cool to 10-15°C, this can lead to damage to underground communications, as well as dangerous freezing of roots. It has been established that the annual temperature difference in the root layer of urban soils reaches 40-50°C, while at the same time in natural conditions (for middle latitudes) it does not exceed 20-25°C.
But it is not only the microclimate that worsens the life of plants in a large city. The most important environmental factor in plant life is moisture. However, in an urban environment, plants often lack soil moisture due to it draining into the sewer system. At the same time, during rain or heavy watering, stagnation of water is possible, which stops the access of air to the roots. Due to the flow of water “past the soil”, the amount of moisture evaporating from the surface of the earth decreases, which leads to a decrease in air humidity up to the so-called “atmospheric drought”.
