Assessment of microclimatic features of the territory. Microclimate of the urban environment

Factors influencing the quality of the microclimate

Practice shows that when creating a microclimate that meets the physiological requirements of certain animals, it is necessary to take into account the entire complex of factors influencing it: climatic and weather, physiological, technical, technological and operational.

Climate and weather affect indoor air quality through their enclosing structures, ventilation, and when opening windows, doors and gates. The technology for keeping certain species and age-sex groups of animals provides for year-round presence in premises, sometimes without walking. Under these conditions, the role of climatic and weather factors increases.

The entire territory of the Russian Federation is divided into 4 climatic regions, which are divided into 16 subregions. When dividing into districts and subdistricts, the following is taken into account:

Average monthly temperature in January (the coldest month);

Average monthly temperature in July (hottest…

Microclimate of the city - section Ecology, ECOLOGY OF THE URBAN ENVIRONMENT Special Microclimatic Conditions are Formed in the City. Microclimate of the City...

Special microclimatic conditions are formed in the city. The microclimate of a city 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 urban elements (walls of buildings,…

How to create a favorable microclimate indoors

It is a rare person who will begin to study the microclimate in his home if everything is fine in his life. But when the children suddenly began to get sick often, their mother developed an allergy to something unknown, and the head of the family himself began to visit doctors frequently, you can’t help but think about it. There must be a reason for all this trouble. And often the cause is an unfavorable microclimate in the living space.

What is the microclimate of a room, what does it consist of?

The term "microclimate" is used to characterize meteorological conditions in a certain relatively small space. In our case, this...

Special microclimatic conditions are formed in the city. Microclimate of the city– this is the climate of the surface air layer of individual sections 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 elements of urban development 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 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 individual 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 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, air 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 an area 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 the bioclimatic characteristics 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, n- 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 .

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Introduction

The most important characteristic of the urban environment is the city’s microclimate, the state of which is determined largely by the anthropogenic impact on the environment and, above all, by its pollution. It affects illumination, the amount of ultraviolet radiation coming from the Sun, humidity, and the frequency of fog formation.

One of the important components of the microclimate that has a noticeable effect on the human body is the air temperature. The average annual temperature in the city is several degrees higher than outside it. In general, the thermal energy released by a large city is very significant and reaches 5% of the solar energy entering the city.

In cities, the amount of ultraviolet radiation decreases (which negatively affects people - increased fatigue, irritability, poor metabolism, etc.). Bacterial air pollution increases. Relative humidity decreases.

In cities there are more windless days, lower atmospheric pressure and wind speed, which leads to stagnation, severe air pollution and an increased incidence of respiratory diseases among the population.

Unorganized parking lots in city centers create additional noise and pollution. The placement of industrial enterprises within cities and their incorrect location in relation to the prevailing winds are also significant. Particularly affected are cities located in poorly ventilated gorges, with frequent low temperature inversions.

Motor transport is the main source of air pollution. The growing level of motorization and increasing mobility of the population are increasingly expanding the zones of human accessibility to natural landscapes, but, on the other hand, these processes contribute to the construction of highways and a more even distribution of recreational loads on the natural environment.

1. Microclimate of the urban environment

The city creates its own local climate, and on its individual streets and squares microclimatic conditions are created, determined by urban development, street covering, distribution of green spaces, and reservoirs.

The formation of urban climate is influenced by:

Direct heat emissions and changes in solar radiation;

Dust and gas emissions from industrial enterprises and transport;

Changes in the heat balance due to reduced evaporation, low permeability of the underlying surface, promoting rapid water drainage and significant thermal conductivity of coatings (roofs, walls of buildings, pavements, etc.);

The roughness of the terrain created by urban development, a large proportion of vertical surfaces, which leads to mutual shading of houses and the formation of basin conditions against the backdrop of flat terrain. Often the cities themselves are located in natural basins.

Table 1.

Climate differences in large cities and surrounding rural areas in mid-latitudes

Solar radiation in large industrial cities is reduced due to reduced transparency due to smoke and dust. Due to an increase in atmospheric turbidity, on average, up to 20% of solar radiation can be lost, and the arrival of ultraviolet radiation is especially greatly weakened. At the same time, in the city, the scattered radiation is added to that reflected by walls and pavements.

Changes in the radiation balance, additional heat entering the atmosphere due to fuel combustion and low heat consumption for evaporation lead to higher temperatures inside the city compared to the surrounding area.

There is a "heat island" above the city. The intensity and size of the heat island varies in time and space under the influence of background meteorological conditions and local characteristics of the city. The most characteristic patterns of air temperature changes during the transition from rural areas to the central part of the city are shown in Fig. 1. At the border between city and countryside, a significant horizontal temperature gradient arises, which can reach 4° C/km.

Rice. 1. Generalized cross-section of a characteristic “heat island” over the city

Most of the city is a "plateau" of warm air with a slight increase in temperature towards the city center. The thermal homogeneity of this plateau is disrupted by the influence of parks and lakes (cold areas) and the dense development of industrial and administrative buildings (heat areas). In the central part of large cities there is a "peak

According to various authors, the thermal influence of cities is clearly manifested within the 100-500-meter layer. At the same time, many common features are found in the city’s climate, sometimes even up to an altitude of 1 km. The high roughness of the underlying surface and the heat island determine the characteristics of the wind regime in urban conditions. With weak winds (1-3 m/s), urban circulation may occur. At the surface of the earth, currents are directed towards the center, where the heat island is located, and at the top there is an outflow of air to the outskirts of the city.

In the city, differences in the heating of illuminated and shaded parts of streets and courtyards determine local air circulation. Ascending movements are formed over the surface of illuminated walls, and downward movements are formed over shadowed walls. The presence of reservoirs in cities contributes to the development of daytime local circulation from the reservoir to urban areas, and vice versa at night.

Rice. 2. Urban circulation developing with weak winds

The wind regime of large cities is characterized by a decrease in wind speed in the city compared to the suburbs. In some cases, wind speeds may increase in the city: in wind directions that coincide with the direction of the street, bounded by multi-story buildings.Green spaces reduce wind speed and promote the deposition of impurities.

Air humidity in large cities is lower than in the surrounding area, which is associated with an increase in temperature and a general decrease in moisture in the atmosphere over the city due to decreased evaporation. Differences in absolute humidity can reach 2.0-2.5 hPa and relative humidity 11 ─ 20%.

Humidity contrasts between the city and its surroundings in the annual cycle have maximum values ​​in the summer, and in the daily cycle - in the evening hours. In the early evening, air in rural areas cools faster and stratification becomes more stable compared to conditions in urban areas. An increase in moisture occurs in the lower layers of air, since evaporation near the ground exceeds the outflow of moisture into the upper layers due to weakened turbulent exchange. During the following night, falling dew reduces the humidity at the ground's surface. In cities, by contrast, combinations of poor dew production, the presence of anthropogenic sources of water vapor, and areas of stagnant air provide greater humidity in urban areas. During the day, developed thermal instability ensures the exchange of moisture between the lower and upper layers of air, and the difference between the city and its surroundings is smoothed out.

In latitudinal zones, where the surface of the earth is covered with snow or frozen in winter, the air in a large city can be more humid during the day, due to anthropogenic sources that provide a significant supply of water vapor to the atmosphere. When considering the influence of a city on precipitation, it is necessary to consider solid and liquid precipitation separately, since the influence of the city on each of these types will be different. During the winter season, differences in precipitation amounts are usually insignificant. In summer, the greatest amounts of precipitation fall over the city, but not in its central part, but on the outskirts. If the air humidity is high enough, then increased convective instability and air pollution over the city contribute to the formation of clouds.

The existing differences in the temperature and humidity conditions of the city ─ suburbs are also manifested in the distribution of atmospheric phenomena. Due to rising temperatures and lower relative humidity, there may be less fog in the city than outside the city.

2.Measures to improve the urban climate

Taking into account the actual climatic conditions of the city and the conditions of the natural climatic zone, measures are taken to improve the urban climate, which can be conditionally divided into the following groups:

• measures to regulate wind speed and ventilation of the city (planning of urban development and streets, orientation of buildings, creation of trees, shrubs and herbaceous plantings of various types, systems of reservoirs, etc.);
• measures to reduce heat loss from buildings (window design, orientation of buildings, planning decisions regarding the relative position of buildings and groups of green spaces);
• measures to regulate relative air humidity (creation of reservoirs and watercourses, increasing the surface area with natural permeable cover, watering green spaces, washing streets and squares, etc.);
• measures to combat air pollution by locating polluting facilities outside the city limits or in the leeward part of cities, creating high chimneys (up to 250 m) that facilitate the dispersion of impurities, efficient use of gas cleaning equipment, switching to less toxic types of fuel, using more economical installations for fuel combustion, regulation or cessation of emissions of harmful substances under unfavorable weather conditions, up to the suspension of enterprises, transition to waste-free or closed production cycles, prevention of dust in industry, construction, transport;
• measures to regulate solar radiation (layout of streets and neighborhoods, green spaces, use of multi-level buildings, painting of walls, roofs and pavements, design of buildings and their elements, etc.).

All these activities must be used in an integrated manner. The use of only individual elements cannot significantly improve the living conditions of people in cities. Solving the problems of improving the microclimate of the urban environment will make cities attractive and safe for life and business, true centers of development of modern civilization.

Job Description

Motor transport is the main source of air pollution. The growing level of motorization and increasing mobility of the population are increasingly expanding the zones of human accessibility to natural landscapes, but, on the other hand, these processes contribute to the construction of highways and a more even distribution of recreational loads on the natural environment.

Economic activity, the layout of residential areas, and a limited number of green spaces lead to the fact that cities, especially large ones, develop their own microclimate, which generally worsens its environmental characteristics.

On windless days, a temperature inversion layer can form over large 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. On windless winter days, the difference in air temperature between the center and the outskirts of St. Petersburg can reach 10° C.

Significant air pollution, in turn, leads to a decrease in insolation and a reduction in the flow of ultraviolet radiation to the earth's surface. This negatively affects the health of city residents, since with reduced insolation, the elimination of a number of toxic substances from the body, in particular heavy metals and their compounds, slows down; in addition, reduced insolation inhibits the synthesis of a number of important enzymes in the body. Meanwhile, residents of large cities very often, especially in winter, experience a lack of insolation.

Particular mention should be made of the unfavorable wind conditions that arise in many areas of new buildings with open construction. It is well known that changes in atmospheric pressure, especially its decrease, have a very adverse effect on the well-being of people suffering from cardiovascular diseases. At the same time, in many areas of new buildings, due to the irrational layout of blocks, local drops in atmospheric pressure may be observed at certain points. Thus, in small gaps between two large houses and at certain wind directions, the speed of wind flows can increase significantly. According to the laws of aerodynamics, at these points there is a local drop in atmospheric pressure (up to tens of millibars), which from the inside of the block acquires a pulsating character (frequency about 5-6 Hz). A zone of such pulsating pressure extends 15-20m to the sides from the gap between the houses. A similar, although less clearly defined, situation is observed on the upper floors of buildings with flat roofs. Needless to say, staying in these areas for people suffering from cardiovascular diseases can negatively affect their health.

The solution to this problem constantly requires the implementation of a set of measures in the areas of new buildings to normalize the wind regime in individual microdistricts through a more rational layout of neighborhoods, the construction of wind protection structures and the planting of green spaces.

Green spaces in cities

The presence of green spaces in cities is one of the most favorable environmental factors. Green spaces actively cleanse the atmosphere, condition the air, reduce noise levels, and prevent the occurrence of unfavorable wind conditions; in addition, greenery in cities has a beneficial effect on a person’s emotional state. At the same time, green spaces should be as close as possible to a person’s place of residence, only then can they have the maximum positive environmental effect.

However, in cities, green spaces are distributed extremely unevenly. Thus, in St. Petersburg, with a total provision of green space of about 20 m2 per inhabitant, the degree of provision of the population with green space ranges from 31.5 m2 per inhabitant in the northwestern regions to 5 m2 in the central regions. It is clear that in the central areas of cities it is almost impossible to find more or less significant areas for expanding green spaces, especially since the available opportunities should be used to the maximum. Here, the most promising is the development of vertical gardening, the possibilities of which are very wide.

Green construction in areas of new buildings also poses considerable difficulties of both a technical and economic nature. The cost of landscaping 1 hectare of territory costs an average of 20 thousand rubles, and the installation of a lawn on the same territory costs 6 thousand rubles. Landscaping small areas costs even more, reaching 10-15 thousand rubles. for 1 m 2. It is clear that in the latter case it is cheaper and easier to asphalt the courtyard area than to landscape it. In technical terms, green construction is hampered by the clutter of the territory of new buildings and the burial of construction waste in the soil. However, the maximum possible greening of urban areas is one of the most important environmental measures in cities.

Concluding the analysis of the main factors shaping the ecological state in cities, let us dwell on one more problem directly related to human ecology. The factors shaping the urban environment were mentioned above; meanwhile, an adult resident of a large city spends the vast majority of time in confined spaces on a weekday - 9 hours. at work, 10-12 at home and at least an hour in transport, shops and other public places and, thus, is in direct contact with the city environment for approximately 2-3 hours a day. This fact forces us to pay especially serious attention to the environmental characteristics of industrial and residential environments.

Creating comfortable conditions in confined spaces and, above all, purified conditioned air and a reduced noise level can significantly reduce the negative impact of the urban environment on human health, and these measures require relatively small material costs. However, not enough attention has yet been paid to resolving this issue. In particular, even the latest residential building designs often do not provide design options for installing air conditioners and air filters. In addition, there are many factors within the living environment that influence its quality. These include gas kitchens, which significantly increase the pollution of the living environment, low air humidity (in the presence of central heating), the presence of a significant amount of various allergens - in carpets, upholstered furniture and even in heat-insulating materials used in construction, and many other factors. The negative consequences of all of the above should not only be taken into account during new construction and major renovations, but active actions to improve the quality of the living environment from every citizen are also required.

One of the climate-forming factors is solar radiation. The arrival of solar radiation on the earth's surface is mainly determined by astronomical factors - the height of the Sun and the length of the day (and therefore latitude and time of year).

The urban environment is in relationship with climatic and microclimatic factors that influence its condition and change under its influence. The main factors influencing changes in natural climatic and microclimatic conditions in urban areas are: air pollution, additional heat, high level of surface coverage with materials with different thermophysical properties, changes in urban conditions (city breezes).

Microclimatic conditions in the urban environment are determined by topography, radiation, thermal and aeration regimes. Assessing the microclimatic regime of the construction site allows us to more correctly predetermine the structural and planning solution and develop a system of reclamation measures in order to improve the microclimate and conduct engineering preparation for urban planning.

When exposed to pollution in the atmosphere, many components of the urban climate change, such as precipitation, humidity, air and soil temperatures, the amount and intensity of fogs, radiation balance, and wind conditions. The ground layer of air in a large city receives 3 times more heat compared to natural landscapes. In general, temperature differences between the city and suburban areas reach 8 0 C (and sometimes more, depending on natural and geographical conditions). Due to differences in temperature and air pressure, artificial breezes arise in certain areas of the urban area.

The radiation regime consists of direct and diffuse solar radiation. Data on the intensity and amounts of direct solar radiation for a particular location can be obtained from. The thermal regime is determined by the total solar radiation and air temperature by calculation in various ways. As a result of urban air pollution, the intensity of direct solar radiation decreases by 20-40%.

Under the influence of development, landscaping elements, landscaping, etc., the aeration regime undergoes strong changes. The main regulator of wind conditions in the urban environment is development. The methodology for quantitative assessment of the aeration regime takes into account the shape and size of wind shadows of buildings and green spaces, and based on data from weather stations at the future development site, the wind regime is analyzed and corrections are made for the terrain.

In particular, the Moscow region, located on the Russian Plain, occupies an area of ​​47 thousand km 2, its population is more than 20 million people, including about 12 million people living in Moscow on an area of ​​1200 km 2. The climate of the Moscow region is characterized as temperate continental, the coldest month is January, when the average monthly temperature in the city center ranges from -8.8 to -9.7 o C, and on the outskirts, from -10.1 to -10. 6 o C, in remote areas of the region 0.9-4.2 o C lower. In the hottest month of the year - July, the temperature in Moscow averages 18.1-19.3 o C, its fluctuations within the city and region are ±0.8-3.2 o C. Snow cover averages 41-45 cm , precipitation – 640-677 mm per year. Winds are predominantly western, southwestern and northwestern, wind speed in the city is 1-1.5 m/s less than in the region; the number of days with calm in the city center is 18, on the outskirts 8-10 per year. The duration of fogs is 141-149 hours per year; air stagnation in the city in winter is most often observed in the mornings, and in summer - in the evenings and at night. Low wind speeds, fogs, and stagnation contribute to the accumulation of pollutants in the city’s atmosphere and prevent their dispersion.

The annual course of total solar radiation is similar to the course of solar heights and day length. An intensive arrival of total radiation in Moscow is observed from May to August (67% of its annual value belongs to this period); the maximum is observed in June (average monthly insolation on a horizontal surface for 1983-2005 was 7.74 kW/m 2 -day), the minimum for the same period (0.71 kW/m 2 -day) is in December. The insolation rate is at least 2 hours of direct sunlight.

For a factor-by-factor and comprehensive assessment of insolation as an environmental factor, it must be taken into account that with continuous sunlight for more than 2 hours, 1 point is taken, from 2 hours to 1 hour - 2 points, and less than 1 hour - 3 points (Table 2), while the significance coefficient in the final calculation has the value KZN = 0.6.