The distribution of precipitation is determined by a number of factors, the main of which are: air temperature, distribution of clouds, features of atmospheric circulation, therefore, it has zonality. The distribution of precipitation on land largely depends on external conditions (terrain relief, nature of the underlying surface).

The western transport of air masses determines the decrease in precipitation to the southeast, but the territory of the Republic of Belarus is small, so this factor is not decisive. The effect of relief is more noticeable.

During all periods of the year, the central part of the Republic of Belarus, which is more elevated, receives more precipitation than the northern and southern lowlands. On the territory of the Belarusian ridge, more precipitation falls in the western part.

On average, 600-700 mm of precipitation falls on most of the republic per year. The central elevated part receives 650–700 mm of precipitation; in some parts of the Belarusian Ridge, the annual amount reaches 750–760 mm. The highest average amount of precipitation was noted at st. Novogrudok - 769 mm (h = 283 m). The lowlands receive 600–650 mm/year. The minimum was noted in the extreme southeast - st. Bragin 566 mm (h = 114 m). The connection of precipitation with the relief is broken only in the south of Belarus, where an increase in precipitation is observed in the left-bank part of the Pripyat (the influence of forest cover).

Despite the sufficient amount of precipitation, in some years on the territory of the Republic of Belarus, both dry phenomena and excessively humidified are observed. This is due to the uneven amount of precipitation, the variability of precipitation.

The maximum annual precipitation at most stations of the Republic of Belarus lies in the range of 850–1000 mm, and at st. Novogrudok - up to 1000-1100 mm. The absolute maximum is marked at st. Vasilevichi in 1906 - 1115 mm.

The minimum annual precipitation in most areas was in the range of 350–450 mm; only in the western uplands did the minimum fall below 500 mm. The absolute minimum amounts are typical for the south and southeast of the republic (298–300 mm). The driest period was 1950–1960, which was also characterized by increased air temperature.

Monthly precipitation has a clearly defined annual course with a minimum in February-March and a maximum in summer months. Precipitation of the warm season is largely associated with heavy rains, so their variability is great. In dry and wet years, the monthly total precipitation may differ by 100–150 mm, and the absolute maximum of the monthly total precipitation for more than 80% of the stations exceeds 200 mm. Such heavy rainfall is most likely in June, July or August. The minimum monthly precipitation of the warm period varies across the territory of Belarus from 1 to 30 mm, and in August 1939, individual stations in the east of the Republic of Belarus recorded their complete absence.

Precipitation falls in liquid, solid and mixed form. In general, for the year the share of liquid precipitation is 70-80%, solid - 10-15%, mixed - 12-13%.

In Belarus, the number of days with precipitation varies from 145 days in the southeast to 193–195 in the central and western regions on the uplands (Minsk, Sventsyansk, Novogrudok). In general, there was a decrease in the number of days with precipitation from the north and northwest to the south and southeast. The maximum is 225-230 days, the minimum is 110 days.

During the year, the maximum is observed in the cold season (from November to January precipitation is possible almost every day) and in July, the minimum is observed in spring and early autumn.

Precipitation intensity is low during the cold season (0.18–0.34 mm/h). Mixed precipitation is the most intense. With the onset of the warm period (V–IX), the intensity of precipitation increases, reaching a maximum in summer (0.026–0.033 mm/min, which is an average of 1.56–1.98 mm/hour). The maximum intensity of precipitation for heavy short-term rains can reach 3.14 mm/min in the Republic of Belarus (it rained with such intensity for 10 minutes) or even 8.7 mm/min (1 min).

Monthly precipitation anomalies. Anomalies are considered large in case of deviation from the monthly norm R n not less than ± 0.4 R n (i.e. Σ< 0,6 R н или Σ >1.4 R n). Such anomalies are observed once every 4–5 years. 1 time in 10 years throughout the country any month can be excessively humid with Σ > 1.7 Rn or dry when Σ< 0,36 R н.

The observed maximum monthly precipitation amounts are 2–3 norms, and only in some cases exceed 4 monthly norms (October 1974 in Brest 564%). The minimum monthly amount of precipitation is 10–20% Rb. Only in August 1039 and November 1993 was there a complete absence of precipitation (east and north of Belarus, respectively).

Drought- a significant, compared to the norm, lack of precipitation over a long period in spring and summer with elevated temperatures air.

In Belarus, droughts are possible from May to September. Dry months are observed when the amount of precipitation is less than 30 mm/month. The most affected are the southern and southeastern parts of the republic. Here, on average, once every 4–5 years, any of the months of the warm period can be dry, and once every 8–10 years - 2 months. contract. In the rest of the territory, droughts are less common (once every 5–10 and 10–15 years, respectively).

The probability of a dry 30-day period increases by 2.5 times. That is, in the south and southeast, every second year can have a drought for 30 days. Droughts in the republic, as a rule, cover 10% of the territory. Only once in 7–12 years, a drought in at least one of the months covers 50% of the country's area. The greatest droughts were noted in 1964 and 1979.

General features of the climate. The climate of any territory is formed due to complex interaction atmospheric processes and the underlying surface. On the territory of Belarus is formed temperate transitional from maritime to continental climate characteristic of the entire East European Plain. The main factors influencing climate formation are geographical position and relief. Features of the climate of Belarus are due to: 1) the location of the territory in temperate latitudes; 2) the predominance of flat relief; 3) proximity Atlantic Ocean; 4) the absence of mountains within the republic and in neighboring regions.

The main features of the Belarusian climate are softness, small temperature amplitudes, sufficient precipitation, and unstable weather. Despite the small area of ​​Belarus, climate indicators vary in different regions of the republic. These include: solar radiation, atmospheric circulation, air temperature, air humidity and precipitation.

Solar radiation. The amount of incoming solar radiation is determined by the angle of incidence sun rays and the length of the day. The angle of incidence of the sun's rays in the north of Belarus is sharper than in the south throughout the year. The length of the day in summer in the north of the country is 1 hour 10 minutes longer than in the south, and in winter the day is half an hour longer in the south. Therefore, the amount of incoming solar radiation in summer is almost the same throughout the territory of Belarus, while in winter the southern regions receive it much more. Total solar radiation increases from north to south. The annual total radiation in the northern regions is about 3600 MJ/m 2 . Southern regions receive more than 4000 MJ/m 2 . The amount of solar radiation varies considerably throughout the year. In June, almost 15 times more solar radiation enters than in December. Summer prevails direct solar radiation(50-55% of the total). In winter and autumn, 70-80% is the share scattered solar radiation.

atmospheric circulation. In temperate latitudes, westerly transport of air masses predominates, therefore, westerly winds are the most typical for Belarus. In connection with the change atmospheric pressure in winter and summer, the direction of the winds changes slightly. In winter, southwest winds prevail, and in summer - northwest (Fig. 33). Such atmospheric circulation determined the predominance throughout the year Atlantic air temperate latitudes . Cloudy weather and rains in summer, snow and thaw in winter are associated with it. The absence of mountains leads to penetration into the territory of the country continental air masses from the east. They usually bring dry weather in winter and summer. Periodically, the territory of Belarus receives arctic air masses , leading to a sharp cooling, and in summer it can penetrate tropical air . characteristic feature atmospheric circulation is the frequent change of cyclones and anticyclones, which leads to weather instability, especially in autumn and spring.

Thermal regime. The climate of Belarus is characterized by positive average annual air temperatures. They gradually rise from the northeast to the southwest from +5.5 to +7.5 °С. Most cold month on the territory of the republic - January. In January average temperature air temperature decreases from southwest to northeast from –3.4 to –7.2 °С. Due to the influence of atmospheric circulation isotherms January have a course close to meridional (atlas, p.13). The Atlantic air warms the south-western regions of the republic to a greater extent. Often in winter temperatures drop to -20 ... -30 °С, and the absolute minimum temperatures that were recorded in Belarus are -36 ... -42 °С.

In summer, the temperature distribution mainly depends on the influx of solar radiation. Therefore, the temperatures of the warmest month (July) increase from north to south. The temperature difference is much less than in winter. In the northern regions, the air temperature in July is about +17 °С, in the southern regions - about +19 °С. The absolute maximum air temperatures are +35… +38 °С.

Air humidity, cloudiness, precipitation. Belarus is characterized by high air humidity throughout the year. This is due to the predominance of humid Atlantic air. In the autumn-winter period throughout the territory of Belarus relative humidity exceeds 80%. In spring and summer due to more high temperatures it drops to 50-60%, and on some days even up to 30%.

High air humidity causes frequent mists arising from relative humidity air 100%. More often, fogs occur in closed basins on hills. More than 70% of foggy days occur between October and March. Significant cloudiness over the territory of Belarus. In the cold half of the year, cloudy weather is observed in 85% of days, in summer - in 50%.

Belarus belongs to the zone of sufficient moisture. Precipitation gradually decreases from northwest to southeast. Precipitation is highly dependent on topography. Therefore, the central part of Belarus, where elevations prevail, receives 650-700 mm of precipitation. The most humid place in the republic is the Novogrudok Upland, where more than 750 mm of precipitation falls annually. In the lowlands of the northern and southern regions of the country, the amount of precipitation drops to 550-600 mm. There are significant fluctuations in precipitation over the years. In dry years, only about 300 mm can fall, and in the most humid years - over 1100 mm.

The warm half of the year (April - September) accounts for 70% of the annual precipitation. Most of the precipitation falls in July, the least - in February, March and January (Fig. 34). On average per year, the number of days with precipitation in the uplands is 180-190, and in the lowlands - 160-170. Most precipitation falls in winter and autumn (November - January). In summer, precipitation is less frequent, but more intense. Quite often they are accompanied by thunderstorms, and sometimes fall in the form of hail.

In winter, precipitation falls in the form of snow and forms a snow cover. Max Height snow cover is usually observed at the end of winter. It increases from southwest to northeast from 15 to 35 cm. The duration of the period with snow cover increases in the same direction from 70 to 130 days. Often in the south-west of Belarus, stable snow cover is not formed.

Seasons of the year and climatic resources

caused the change of seasons. According to the calendar, the length of all seasons of the year is 3 months. But the beginning phenological pore year in Belarus usually does not coincide with calendar dates. It is determined by significant changes in nature, due to the temperature regime. The timing of their onset varies considerably from year to year. However, long-term observations make it possible to determine the beginning and duration of the seasons in Belarus (Fig. 35). The greatest differences are observed when comparing the southwestern and northeastern regions of the country.

Start spring related to date sustainable transition average daily air temperature through 0° during temperature increase. Spring usually starts in March. In the south-west of the republic - in early March, in the north-east - in last days month. Phenological spring is the shortest season of the year. It usually lasts from 35 to 45 days. Air temperatures are rising very quickly. The amount of precipitation is increasing. There are such phenological phenomena as floods on rivers, the arrival of birds, the movement of sap in trees, etc. (Name what other phenological phenomena are characteristic of spring.) The weather in spring is very unstable, due to the frequent change of cold and warm air masses.

Phenological summer a period of time with stable average daily air temperatures above +12 °C is considered. Summer comes in early May in the south-west of Belarus and in mid-May in the north-east. For most of the country, summer is the longest season of the year (140 to 160 days). More than half of the annual solar radiation comes in during the summer. Air temperatures usually exceed +15 °C, and sometimes rise above +30 °C. In May and early June, as well as at the end of August, frosts can be recorded. In summer, 2-3 times more precipitation falls than in winter. Precipitation is usually intense, often accompanied by thunderstorms.

Autumn belongs to the transitional seasons of the year and slightly exceeds spring in duration. Phenological autumn begins in the second half of September, when stable average daily air temperatures drop below +12 °C. It lasts 45-55 days until the air temperature passes below 0 °C. In autumn, the day length is shortened, frosts are often observed. Distinctive feature autumn - activation of cyclonic activity. This leads to more frequent rains, sometimes protracted, drizzling. Almost every year there is a period of warming air, the so-called "Indian summer". The most characteristic phenological phenomena of autumn are the departure of migratory birds and the end of the growing season of plants.

Winter begins in the second half of November after a steady transition of average daily temperatures through 0° downwards. This is the second longest time of the year (105-145 days), and in the north-east of the country it is even longer than summer. A short day and a sharp angle of incidence of the sun's rays lead to a small influx of solar radiation. The air temperature depends on atmospheric circulation, so the isotherms have a meridional direction. Winter is mild, with frequent thaws, the number of which is 8-9. Due to negative temperatures, snow cover is established throughout the country. Much more in winter cloudy days and precipitation falls more often, but their intensity is low. (Remember what phenological phenomena are characteristic of winter.)

climate resources. The climate of Belarus is favorable for human economic activity. Climatic indicators that are used in human economic activity refer to climate resources . The terms of use of many modes of transport depend on them. Wind and solar energy can be used for energy purposes. Climatic resources determine the possibility of building economic facilities, roads, using the territory for recreational purposes, and have an impact on human health. But first of all they affect agriculture.

Agro-climatic resources Belarus are characterized by the following indicators: duration vegetation and frost-free periods, the number of days with average daily temperatures above +5 and +10 °C, the sum of temperatures for these periods, the amount of precipitation for the year and the warm period, the conditions for overwintering winter crops.

The growing season corresponds to a period of time with temperatures above +5 °C. In Belarus, its duration is from 184 days in the northeast to 215 days in the southwest (see Fig. 35). An almost monthly difference leads to differences in the vegetation of these territories.

The frost-free period is usually shorter, since frosts are also observed at fairly high positive average daily temperatures. On the territory of Belarus, it is 145-165 days.

Important indicators of the characteristics of agro-climatic resources are the sums of temperatures above +5 °C and +10 °C. They gradually increase from north to south from 2500° to 2900° and from 2100° to 2500°, respectively (atlas, p. 14).

Belarus has enough rainfall to grow crops. During the warm period, 350-500 mm of precipitation falls. The lack of moisture is recorded only in the southeast of the country in summer. Thus, agro-climatic resources favor the development of crop production in the country.

Climate change. Human economic activity has everything greater influence on the climate of the republic. This is manifested in climate warming, air pollution in major cities and industrial centers.

In the last two decades, there has been a slight decrease in precipitation in the south and in the central part of the country. In the north of the country, the amount of precipitation in both cold and warm periods increased. The contrast in the amount of precipitation increased: areas with an annual precipitation of less than 600 mm and more than 700 mm expanded. An increase in the number of extreme climatic events. In the southern regions, the number of droughts in the second half of summer has doubled over the past 50 years.

Bibliography

1. Geography grade 10 / Textbook for grade 10 institutions of general secondary education with the Russian language of instruction / Authors: M. N. Brilevsky- From the Authors, Introduction, § 1-32; G. S. Smolyakov- § 33-63 / Minsk "People's Asveta" 2012

/ Climate of Belarus

Climate of Belarus

The climate of Belarus is temperate continental. In general, the climate of Belarus is quite mild and humid. In winter, thaws are not uncommon here, which is why the thickness of the snow cover is rather small, although, in forest areas, snow falls up to 1-1.2 meters.

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The most climatically favorable are the Brest and Grodno regions. It's moderate here humid climate, with soft short winter and moderately warm long summers - practically, this is the climate of Europe. The warmest point of Belarus is located in the same area.

The climate of Minsk and Mogilev regions can be compared with the climate of the central part of Russia. Here more Cold winter and fairly hot summers. The most severe climate is in the Vitebsk region - the continental climate is more pronounced here than in other regions of Belarus.

Significant cloudiness over the territory of Belarus is also associated with the high humidity of the climate. In the autumn-winter period, cloudy skies prevail about 85% of the time, and in the spring-summer period, cloudiness decreases, in May - August the sky is cloudy 40 - 60% of the time, which is quite a lot for this latitude. The maximum of clear days falls on April - May, and in the southeast of Belarus - on July - September.

Winter in Belarus begins in early December. In general, the Belarusian winter is rather mild and moderately cold. In December, the weather is cold in winter. The average daily air temperature in December is -2 - -3°С, dropping to -4 - -6°С at night. Over most of the country, precipitation falls mainly in the form of rain with wet snow. And by the middle of the month, snow cover is established throughout the republic. In general, the snow cover is quite stable, however, from time to time, thaws occur, especially relevant for December, when everything is actively melting, but after a few days the frosts return, and this leads to severe black ice.

In December in Belarus, the sun peeps out in the sky extremely rarely, cloudy weather persists, which is often accompanied by thick fogs. Another unpleasant feature of December is the wind, which often blows from the southeast at a speed of 4 m/s, and sometimes its gusts reach 15 m/s.

Increased cloudiness in Belarus is also observed in January. This month is considered the coldest of the year. The average daily air temperature in January is -5 - -7°C, real frosts can happen, but often, even this month, thaws come to the country for a short time. At night, the air temperature usually does not fall below -10°C, but in the northern part of the country there are cold snaps down to -16°C.

The weather in February is a little more comfortable than in January, but, in general, it is the same cold winter month. The average daily air temperature in Belarus in February is -5°C, dropping to -10°C at night, but the possibility of thaws this month is also quite high. There is an increased humidity - about 80%, quite often there are unpleasant precipitations in the form of snow and rain. For Belarus, strong winds in February are not typical, as, for example, this is typical for central Russia. The wind speed here usually does not exceed 3 m/s. In February, the number of hours of sunshine also increases.

Spring in Belarus comes at the beginning (rarely in the middle) of March. Spring is in no hurry to come into its own here. The average daily temperature in March is 0 - +2°C, but at night it is still cold here - the temperature drops to -5 - -7°C. The snow cover begins to melt only in the middle - the end of March. Due to heavy snowmelt, some settlements are flooded due to high water on the rivers, therefore, transport connection with them is often violated.

In March, there is a decrease in humidity to 60%, which is much lower than in the winter months. It often rains and snows. The length of the day, this month, increases significantly, as does the number of hours of sunshine per day.

In April, in Belarus, the temperature is slowly but surely gaining momentum. The average daily air temperature is +7 - +10°C, sometimes warming up to +15°C, and at night it stays within +2 - +5°C. The influence of spring is already more noticeable than in March. The daylight hours and the number of hours of sunshine are increasing. In the northern part of the country, snow lies until mid-April, in the south of the country, snowmelt occurs much faster. Precipitation falls mainly in the form of rain, less often snow, snowfalls in the second half of April are rare.

Real spring comes to Belarus in May. The air becomes humid and warm. Installed sunny weather. Leaves bloom, grass turns green, the first plants bloom. May is a very fertile time in Belarus. The average daily air temperature in Belarus in May is +15 - +18°С, dropping to +10°С at night. Sometimes there are sharp cold snaps, night frosts in May are also not uncommon for Belarus. Atmospheric pressure, in May, is usually stable and is about 750 mm Hg. Art.

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Summer in Belarus begins in early June. In general, the Belarusian summer is moderately warm and rather rainy. In June, there is especially an active rise in temperatures. The average daily air temperature in June in Belarus is +21 - +23°С. Despite the hot weather in daytime, in the evening the air may seem cool, and at night the thermometer, at all, drops to +10 - +15 ° С. It is in June that the longest daylight hours are observed - it is about 13 hours. In June, there is quite a lot of precipitation in Belarus - as a rule, these are heavy short rains, often accompanied by thunderstorms.

July is the hottest month in Belarus, and one of the rainiest months. On average, there are up to 15 rainy days per month, and 10 of them with thunderstorms. Rains are often accompanied by squally winds at speeds up to 19 m/s. The average daily air temperature in July in Belarus is +23 - +25°С, and at night, only +15 - +17°С.

August is the last summer month in Belarus. In August, the number of hours of sunshine prevails, since this month there is less rainfall than in July. The average daily air temperature in August in Belarus is +22 - +24°С, and at night it drops to +13 - +15°С. The contrast between day and night air temperatures is very noticeable. Basically, the weather in Belarus in August is partly cloudy and warm, and there are very few rainy days.

Autumn in Belarus begins in early September. The first half of September is quite comfortable for staying in the country, as a rule, the weather is quite warm, sunny and dry. But, in the middle of the month, autumn comes into its own. It's getting colder outside, the sun is hiding behind the clouds almost all the time, and the trees shed their golden foliage.

The average daily air temperature in September in Belarus fluctuates between +12 - +16°С. The night temperature is only +5 - +10°C. Hot weather in September is rare. Short-term rains pass in the second and third decade of the month. AT last week September usually sees a significant drop in temperature, and frosts begin in most of the country.

In October, cool and cloudy weather prevails in Belarus. The peculiarity of this month is strong winds, which often reach 15 m/s. The average daily temperature in October in Belarus is +9 - +11°C, and at night it drops, on average, to +5°C. In the second half of the month, there is an increase in rains, sleet can fall, there are several days with fogs. There is very little sun in October, and the daylight hours themselves are significantly reduced.

November is a cold cloudy month in Belarus. In November, for the first time, the thermometer falls below 0°C, during the day it is very cold, rain with sleet is possible. Frequent guests of November are dull fogs, as a result of which, humidity and, accordingly, cold intensify. The average daily air temperature in November is +4 - +6°C, and at night +1 - +2°C. In the second half of the month, at night, slightly negative air temperatures are possible, and frosts and snowfalls become frequent guests. However, the snow cover does not last long, the earth is still warm. There is practically no sun in November, and the daylight hours are very short. Nature is rapidly preparing for the coming winter...

Belarus belongs to the zone of sufficient moisture. The average annual amount of precipitation is 500 - 600 mm in the lowlands, and 600 - 700 mm in the plains and uplands. About 70% of precipitation falls during the warm season (from April to October), mainly in the form of rain. A significant amount of precipitation, relatively low temperatures cause high humidity air, and high humidity air, in turn, leads to frequent fogs. The average annual number of days with fogs varies from 35 to 100, depending on the height of the area above sea level.

When to go to Belarus. The best time to visit Belarus is the warm months - from May to the end of September. All these months are great for both rest and treatment in boarding houses and sanatoriums in Belarus, and for sightseeing tours around the country, since the summer in Belarus is not very hot, you can move around comfortably, seeing local sights. It is worth remembering that during the summer months in Belarus high season, millions of tourists rush at this time for treatment and recreation in the country's sanatorium, therefore, it is recommended to book places 3-4 months before the start of the trip. It is also worth remembering that prices in the summer season are somewhat overpriced: some resorts and hotels set a price tag 1.5 - 2 times higher than the standard rates in the off-season.

The summer months, from June to September, are great for outdoor recreation, fishing and swimming in local lakes and rivers. It is worth remembering that, even in the summer months, it is quite cool here in the evening and at night, therefore, it is recommended to always have a supply of warm clothes with you.

Winter Belarus is a ski paradise. December to March, in the country ski season therefore, lovers of skiing rush here. Ideal coverage on the slopes is maintained with the help of an artificial snow system. Also, the winter months are very popular among those wishing to treat their health in sanatoriums. It is worth noting that prices in winter for holidays in Belarus are quite acceptable and much lower than, for example, in summer. Winter excursion tours in Belarus, they are also quite popular with tourists - winters are mild here, frosts are rare, and nature appears in snow-covered splendor.

Not best time for a trip to Belarus early spring (March, April) and late fall(October November). These four months are extremely unstable and very unpredictable, both in terms of weather and air temperature. Strong winds and dank rains will certainly spoil your mood and force you to sit in your room. However, these months are not bad for a spa holiday, in addition, the prices for rest and treatment will be the lowest.

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General characteristics of the main climate-forming processes and factors

The main features of the Belarusian climate are determined by the geographical position of the country in the middle latitudes, relative proximity to the Atlantic Ocean, the prevailing western transport of air masses and flat relief, which does not prevent the movement of air masses in different directions.

The main climate-forming processes in the country are:

- heat transfer

– moisture circulation,

- General circulation of the atmosphere.

The joint action of these processes determines in general terms the features of each meteorological element and the climate as a whole: the course of temperatures, cloudiness, precipitation, etc.

A certain impact on the climate of the territory of Belarus has a modern economic activity people, which is especially noticeable on the banks of large reservoirs, in areas of large urban settlements, on drained peat bogs and in places where certain mineral deposits are developed.

The territory of Belarus is located in the western region of the northern temperate zone and has a temperate continental climate. The geographic latitude of the territory (Belarus is located between 56 0 and 51 0 N) determines the angle of incidence of sunlight, the length of the day and solar illumination, which, in turn, affect the amount of incoming solar radiation.

The angle of incidence of the sun's rays at noon during the year changes by 47 0: on the day of the summer solstice in Minsk, it reaches 59 0 30̍ ", and on the day winter solstice decreases to 12 0 30̍". In the days of spring and autumn equinox the angle of incidence of the sun's rays is 36 0 .

The length of the day within Belarus varies by more than 10 hours, in winter it is longer in the south, and in summer - in the north. The difference between the north and south of the country in winter and summer is about one hour per day. In Minsk, the longest day - June 22 - lasts 17 hours 11 minutes. Features of changing the angle of incidence of the sun's rays and the length of the day lead to noticeable differences in the amount of solar radiation received by the northern and southern regions countries (both in annual output and by seasons of the year).

Solar radiation

The amount of solar radiation reaching the earth's surface depends primarily on the height of the Sun above the horizon, the length of the day and cloud cover, which determines the duration of sunshine and the amount of direct solar radiation.

The arrival of solar radiation decreases in the direction from south to north from 4,100 to 3,500 MJ/m 2 per year.

Reference: Joule is the SI unit of energy, work and heat, named after J. Joule. It is designated J. 1 J = 10 7 erg = 0.2388 cal.

In the annual course of total radiation, significant deviations are observed both in quantity and composition from its average annual indicators. In July, solar radiation is 9 times greater than in January and 50–52% consists of direct solar radiation. In January, direct radiation accounts for only 20–30% of the total value. Under the influence of cloudiness, the share of direct solar radiation can be reduced to 12 - 17%.

The intensity of solar radiation also depends on the transparency of the atmosphere, i.e. against dust, water vapor, aerosols, etc. The transparency of the atmosphere varies significantly with the seasons of the year.

Atmospheric transparency increases from summer to winter and reaches maximum values ​​in November-December (first maximum) and in February (second maximum). However, due to significant cloudiness in the winter season, the duration of sunshine is significantly reduced.

The sunniest months in Belarus are June and July. It is during these summer months that the maximum values ​​of direct solar radiation fall. An average of 1,500-2,000 MJ/m 2 of direct solar radiation falls on a horizontal surface per year in Belarus.

Thus, the ratio of direct and diffuse solar radiation changes throughout the year. In almost all months, direct radiation is less than diffuse. This difference is especially significant in the winter season. And only from May to July, the proportion of direct radiation is slightly higher than diffuse.

In the annual course of total radiation, the maximum in July and the minimum in January are well pronounced (in Minsk - 623 and 40 MJ/m2).

A sharp increase in total solar radiation is usually observed in March due to an increase in the angle of incidence of the sun's rays, an increase in day length and a decrease in cloudiness. In connection with these circumstances, almost 50% of the annual total radiation falls on May, June and July, and only 5% on November, December and January.

It also has its own characteristics daily course total radiation. In summer, when the length of the day doubles, solar radiation reaches the earth's surface for a longer time. For example, in June it increases to 21:00 and reaches a maximum around noon. In Minsk, for example, on clear June days, an average of 3.17 MJ / (m 2 hour) enters per day, and in December - only 0.71 MJ / (m 2 hour). The absolute midday maximum is observed in May (3.93 MJ / (m 2 hour)), when the air contains a minimum amount of water vapor and aerosols. But the daily amount of radiation is still higher in June.

In the total course of total radiation great importance has clouds. In summer, with a clear sky, the value of total radiation is 50% higher than in conditions of average cloudiness.

The maximum daily radiation with average cloudiness in June in Minsk is about 20.79 MJ/m 2 , and in December - up to 1.34 MJ/m 2 .

Radiation and heat balance

Total radiation and atmospheric radiation make up the incoming part of the radiation balance, and reflected radiation and terrestrial radiation make up the outgoing part.

Reflectivity earth's surface determined by the albedo. The albedo, which depends on the nature of the underlying surface, varies significantly with the seasons of the year. In the warm part of the year, the earth's surface covered with grassy vegetation reflects about 20% of the incoming total radiation, in November - 30-40%, and in January-February, when there is a stable snow cover - up to 60-70%. A significant increase in albedo in winter time year leads to a reduction in the proportion of radiation absorbed by the underlying surface.

The amount of absorbed radiation determines the effective radiation, i.e. the difference between the long-wave thermal radiation of the underlying surface and the oncoming atmospheric radiation. The maximum effective radiation is observed in May-July and is more than 30% of the absorbed radiation. But at the same time, the incoming part of the radiation balance, the total radiation, also reaches its maximum values. The minimum of effective radiation is recorded in December, when the total radiation receives the minimum amount.

In general, 40-45% of the absorbed radiation is lost in the form of effective radiation per year, which is 1,100 MJ/m 2 in the northern regions of the country, and 1,300 MJ/m 2 in the southern regions.

During the day, the effective radiation is higher than at night, but during the day, the heat gain is also greater. During cloudless night hours, due to effective radiation, radiative cooling (cooling) of the earth's surface can be observed, which leads to frosts in spring and autumn.

Thus, the ratio between the total radiation, albedo and effective radiation determines the radiation balance of the earth's surface: positive or negative.

On the average annual output, the radiation balance in the territory of Belarus is positive and increases from the northeast to the southwest from 1500 MJ/m2 to 1800 MJ/m2. Four months of the year (November-February) in the northern and central parts of Belarus and three months (November-January) in the southern part of the country, the radiation balance is negative. In March and April, the radiation balance sharply increases as a result of rapid growth total radiation and albedo reduction due to snow cover melting. Then the growth of monthly amounts slows down significantly. The largest average total value of the radiation balance falls on June. In Minsk, for example, this value is about 329 MJ/m2.

By autumn, the radiation balance decreases and in November it becomes negative. The transition to positive average daily amounts of the radiation balance occurs in February.

During the day, the radiation balance is positive (with the exception of the winter months); at noon it everywhere reaches a maximum, and at night throughout the year it is negative.

Positive radiation balance on the territory of Belarus lasts 9 months. The radiation balance is spent mainly on:

1) evaporation

2) turbulent heat exchange between the underlying surface and the atmosphere.

On average, 84% of the radiation balance is spent on evaporation and 16% on heat exchange.

Atmospheric pressure. Air mass circulation

The most important climate-forming process on the territory of Belarus is the western transport of air masses. With the western transport from the Atlantic Ocean, along with cyclones formed on the polar (moderate) and Arctic fronts, moderate sea air masses come. Arctic and tropical air masses have a much lesser effect on the country's climate.

It is known that the movement of air masses depends on the characteristics of the baric field, the distribution of pressure during the year, and the position of baric centers over the mainland and adjacent parts of the World Ocean. In turn, the pressure over the territory of the country is formed under the influence of the general circulation of the atmosphere.

In winter, the Asian High forms over Eurasia. The repeatability of weather in winter, which is established under the influence of the Asian anticyclone, is 18-20%, in spring and autumn - 10-14%. The intensity of the influence of the Asian anticyclone decreases in the direction from east to west.

In summer, the Azores High, which is constantly located in tropical latitudes, shifts to the north and its eastern branch passes south of Belarus. The Azores High as a whole determines the nature of the country's weather in the summer. The recurrence of weather in summer, which is established under the influence of this anticyclone, is about 18%.

On average, 15–16 anticyclones come to the territory of Belarus or form directly above it per year. Cyclones have a more noticeable impact on the climate of Belarus.

The impact of cyclones on the conditions and nature of the weather is detected for 150–160 days a year. The cyclonic circulation affects the weather for about 216 days. Cyclones are known to form on the Arctic and Polar fronts, but can also occur as a result of uneven heating of the earth's surface.

The interaction of baric maxima and minima, the formation of anticyclones and cyclones, the trajectories of their movement determine many atmospheric processes on the territory of the country: the features and distribution of the baric field, the prevailing transport of air masses, advection of heat and cold, the amount and mode of precipitation.

Atmospheric pressure gradually increases from the north and northwest to the south and southeast. For example, in Vitebsk it is 994.9 Pa, and in Gomel it is 1001.5 Pa. The average pressure at sea level is 1013.2 Pa.

Reference: Pascal (Pa) is the SI unit of pressure and mechanical stress, named after B. Pascal; marked Pa. 1 Pa \u003d 1 N / m 2 \u003d 10 dynes / cm 2 \u003d 0.102 kgf / m 2 \u003d 10 -5 bar \u003d 7.50x10 -3 mm. rt. Art. = 0.102 mm w.c. Art.

The maximum pressure over the entire territory of the country is set in January. January isobars run from the southwest to the northeast. In the summer, over warmed land, the pressure decreases. Within the territory of Belarus, the drop in atmospheric pressure in summer occurs from west to east. The lowest atmospheric pressure in the country is recorded in July.

The annual course of atmospheric pressure leads to the fact that in summer the winds of the western and north-western directions prevail, and in the winter - the western and north-western directions. In the system of the general circulation of the atmosphere, there is a periodic change from the zonal western transport of air masses to the meridional transport with the movement of air masses from south to north or from north to south. The nature of atmospheric circulation determines the type and properties of air masses entering the country.

Moderate air masses dominate the territory of the country throughout the year.

In winter, western and southwestern winds bring mainly sea air. Marine air masses enter the territory of Belarus with cyclones that originate over the Atlantic Ocean and the Mediterranean Sea on the Arctic and moderate (polar) fronts. In winter, maritime air masses dominate over the territory of Belarus for 50–60% winter period. The intrusion of temperate marine air is accompanied by warming, thaws, cloudiness, increased humidity and precipitation. In summer, temperate maritime air comes mainly from the west and northwest. It also brings moisture, but, being colder, generally lowers the temperature. Moving to the east, sea air masses quickly warm up and transform into warm continental air.

Continental temperate air that forms only over land; it penetrates the country from the east and southeast and brings a cold snap in winter, and warming and dryness in summer. The highest frequency of temperate continental air is typical for the north-eastern part of Belarus.

Arctic air masses reach Belarus in a system of cyclones formed on the Arctic front and moving mainly in east and northeast directions. Arctic air masses that form over Svalbard and Greenland, moving over the warm surface of the Atlantic Ocean, acquire the properties of sea air masses. Colliding with moderate air masses, they form cold fronts, which are accompanied by precipitation, increased northerly winds and a decrease in air temperature.

Continental arctic air masses come to Belarus from the northeast, from the Kara and Barents Seas, bringing strong winds and heavy snowfalls.

Arctic air masses are over the territory of Belarus about 40-70 days a year; in winter and summer they cause cooling, in spring - late frosts, and in autumn - early frosts.

Tropical air masses are less typical for Belarus than temperate and arctic ones. Their average frequency is about 20–25%. Tropical air masses come to the country in summer from the southwest and southeast.

More often, maritime tropical air masses penetrate the territory of Belarus, which bring relatively high temperatures and high humidity.

Continental tropical air enters the country much less frequently.

Thus, the climate of Belarus is characterized by the influx of various air masses that bring heat or cold and determine precipitation. Change of air masses, interaction of cyclones and anticyclones, dynamics atmospheric fronts cause changes in temperature and instability of the weather regime.

Air temperature

The main result of the western transfer is heat advection in the winter period of the year, which largely smoothes the average annual temperature amplitudes. In general, the following regularity is observed in the annual course of temperatures: average annual temperatures rise from the northeast (4.4°С) to the southwest (7.4 0 С). Annual isotherms run from northwest to southeast. In the same direction, the duration of the warm period also increases, reaching 250–260 days in the southeast. In the northwest, the duration of the warm period is about 220–230 days.

The air temperature in the country is characterized by variability and inconstancy. The minimum average monthly temperatures are observed in January, and the maximum - in July. In Minsk, for example, the average long-term temperature in January is -6.9°C, but once every four years it is lower - 9°C or higher - 4°C. The average long-term temperature in July in Minsk is + 17.8°C, but once every 30 years it exceeds + 30°C.

The absolute maximum of about 38°C was recorded in the southeast of the country in June 1956 (Vasilevichi, Lelchitsy, Zhlobin), and the absolute minimum of 44°C was recorded in the north of the country in 1940 at Luzhesna station (Vitebsk region ).

The January isotherms are elongated from northwest to southeast. Most low temperatures(-8.5°С) of January are observed in the northeast, the highest (-4.5°С) - in the southwest.

The July isotherms are close to the latitudinal strike, which is explained by the latitudinal inflow of solar radiation. In July, the temperature rises from 17°C in the north to 19.7°C in the south (Komarin settlement).

The annual temperature amplitudes increase from west to east (23°C and 26°C, respectively) and show an increase in climate continentality.

The daily course of temperatures on the territory of Belarus also has its own specific features. In the diurnal course of temperatures, the maximum is observed in the afternoon, at about 15–16 hours, and the minimum is observed before sunrise. The amplitudes of daily temperatures depend mainly on cloudiness: they are the largest in clear skies, and the smallest in cloudy skies.

The winter period in the country is characterized by frequent thaw, associated with the arrival of moderate sea air masses. The number of days with thaws decreases from 40–50 in the southwest to 23–30 in the southeast (7,36,37,49,105,108,109).

Precipitation

The circulation of air masses and the thermal regime determine the features of moisture circulation and the regime of precipitation.

The annual course of absolute humidity generally coincides with the annual course of temperatures: the maximum is observed in summer, and the minimum is observed in winter. Relative humidity reaches its minimum in winter and is 88–90%, while in spring and summer it drops to 65–70%. The average annual relative humidity is about 80%. The lowest relative air humidity (about 30%) is observed in May and June, which leads to dry weather (especially in the southeast of the country).

The daily variation of relative humidity is best expressed in summer: the maximum is observed before sunrise, and the minimum is observed at 15–16 hours. In this case, the relative humidity amplitude can reach 25–40%.

Condensation of water vapor contained in the atmosphere leads to the formation of clouds, fogs and precipitation. a huge role cloudiness is formed by ascending movements (sliding) of air masses along the line of atmospheric fronts in cyclones.

Cloudiness, as you know, is determined by the amount and shape of clouds and is expressed in points or percentages. Cloudiness is measured by the number of cloudy days per year.

The number of cloudy days in Belarus ranges from 135 in the southeast to 175 in the northwest of the country per year. At elevations that retain moisture, cloudiness increases significantly.

The annual course of cloudiness and the cloudy state of the sky as a whole coincides with the annual course of relative humidity, reaching a maximum in winter (more than 80% of days with cloudy skies) and a minimum (about 45–55% of days) in summer.

During the cold period of the year, the maximum frequency of cloudy skies is observed in morning hours, and the minimum - in the evening. In the warm period of the year, the maximum frequency of cloudy skies is observed during the day, and the minimum is observed at night. Predominant in autumn and winter stratus clouds, and in summer - cumulus and pinnate.

The high frequency of fogs is also associated with high relative humidity. On the territory of Belarus, from 35 to 100 days a year with fogs are recorded. Fog forms at a relative humidity close to 100% in the absence of wind or at very light wind. Most often, fogs occur in closed basins, on lakes or swamps.

The territory of Belarus is located in a zone of sufficient moisture. The average annual rainfall ranges from 500 to 700 mm per year. The distribution of precipitation is influenced by the relief and the nature of cyclonic activity. Precipitation increases at higher elevations, especially on their windward slopes. The lowlands and lee slopes of the uplands receive much less precipitation. In general, the following main regularity can be traced in the distribution of precipitation over the territory of Belarus: the amount of precipitation decreases from the northwest to the southeast.

The average annual precipitation in the center and north-west of the country is 600–650 mm, and in some areas it rises to 700 mm. The windward slopes of the Novogrudok Upland receive the most precipitation (more than 700 mm of precipitation per year). In the extreme west, southwest and south, the smallest amount of precipitation for Belarus falls - 500–550 mm.

On the territory of the country, significant deviations from the average long-term data are quite often observed. In dry years, the amount of precipitation can decrease to 300 mm or less. For example, in 1961, only 280 mm of precipitation fell in Pinsk. Maximum amount precipitation was recorded in 1906 near the city of Vasilevichi, Gomel region and amounted to about 1016 mm.

The annual course of precipitation is close to annual course temperatures and absolute humidity. The wettest months of the year in the country are July and August, and the driest months are January and February. About 70% of all precipitation falls in warm season years from April to October.

On average, there are 160-190 days with precipitation in the country. In the winter-autumn period, due to a decrease in air temperature, drizzling rains and low-intensity snowfalls often occur.

climatic regions

Climatic zoning is based on the following criteria:

1) total temperatures above 10°C,

2) indicators of moistening of the territory (the ratio of the amount of precipitation and evaporation).

Based on these criteria, the following climatic regions are distinguished on the territory of Belarus:

1. North - moderately warm, humid;

2. Central - warm, moderately humid;

3. South - warm, unstable wet.

Climatic regions, in turn, are divided into separate sub-regions.

The northern region occupies the northern part of the country and is located north of the isoline of the sum of temperatures above 10°C equal to 2200°C. The northern region almost coincides with the Belarusian-Valdai physical-geographical province. Within this region, the humidity coefficient in the warm period of the year is somewhat higher than unity. The air temperature in July is 16.5–18°C, and in January -6.5–8.5°C. The duration of the spring-summer period is 133–145 days, and the duration of the growing season is 178–188 days. This area often experiences spring and autumn frosts. Here the snow lies longer, the soil freezes deeper. According to its temperature regime, the region is moderately warm. On average, about 600 mm of precipitation falls per year; on hills - 650 mm and more. The region does not feel a lack of moisture during the growing season of plants.

The central region is central part countries. The sum of temperatures above 10°C here reaches 2400°C ( southern border areas). The moisture coefficient in the warm period of the year is 0.9. The central region is warmer and less humid than the northern one. For example, the average temperatures in July are 17.6 - 18.7°С, and in January they change from -4.9°С in the west to -8.2°С in the east. Precipitation within this area falls 500 - 600 mm, and only in some places - up to 700 mm.

The southern region is southern part country, lies within the Polessky physical-geographical province and is characterized by warmer conditions than the northern and central regions. The sum of temperatures above 10°C within this region ranges from 2400 to 2500°C, the humidification coefficient in the warm period of the year is 0.8–0.9. Average temperatures in January vary from -4°С in the west to -7°С in the east, and in July - from 18°С in the west to 19.5°С in the east of the region. Spring and summer in this area come much earlier than in the northern and central regions. The growing season is 191–209 days. Precipitation falls from 520 to 630 mm. Within the southern region, there is some moisture deficit in the summer period and therefore this region is considered as unsustainably humid.

Each region according to the degree of continentality is divided into:

1) western (less continental)

2) eastern (more continental) subregions.

The degree of continentality is determined by the number of days with air temperatures from 5 to 15°C. In the western sub-regions, there are more than 40% of such days per year, and in the eastern sub-regions - less than 40%.

Climate of Belarus temperate continental. The predominance of plains in Belarus and the absence of large elevations facilitate the flow of sea air masses from the Atlantic and continental air masses from the east and northeast. The first bring frequent thaws and snowfalls in winter, cool rainy weather comes with them in summer. The latter often cause increased winter frosts and summer heat. However, due to the influence of maritime air masses, prolonged heat and drought are as rare as prolonged persistent frosts in winter, and frequent weather changes occur at all times of the year. The climate of Belarus is quite uniform throughout the territory, but from north to south, the average air temperature gradually rises. From west to east, the amplitudes of average monthly temperatures increase. If in the west (in Brest) they are 23.2 "C, then in the east, in Gomel -25.5" C. The change of seasons is well expressed on the territory of Belarus. In winter, the warmest place is the southwest: the average January temperature in Brest is -4.4 "C. The coldest winter is in Vitebsk, where the average January temperature is -7.8" C. In summer the most warm places in the southeast, the coolest - in the north. The annual amount of precipitation ranges from 500 (southeast) to 700 mm (central highlands), maximum precipitation in July (60-90 mm), minimum - in February (25-40 mm). The number of days without sun fluctuates here within 100-120, fogs are frequent (50-80 days a year).