1. Basic characteristics of climate
The basic characteristic of European climate is that it is predominantly oceanic. Although Europe is located in mid-to-high latitudes, its winters are not as cold as those in northern Asia. While Siberia is in the severe cold of -30 to -40°C, most European areas at the same latitude are above -15°C, or even around 0°C. It's not too hot in summer either. The seasonal distribution of precipitation in Europe is relatively even, and there is no distinction between dry and wet seasons in most areas.
In addition, the temperate maritime climate of Western Europe and the Mediterranean climate of Southern Europe not only have distinctive characteristics, but also cover a wide range.
2. The main factors that shape the European climate
(1) Geographic factors
The above characteristics of the European climate are caused by the combined influence of many factors , among which geographical location plays the largest role.
The European continent is located between 36° and 71° north latitude, and together with the surrounding islands, it is roughly between 35° and 80° north latitude. Most of the continent is located in the northern temperate zone, so the temperate climate is dominant. The scope of the cold zone climate is very limited and there is no tropical climate.
Europe’s latitude is in the westerly belt of the planetary wind system. At the same time, Europe is located on the west coast of the continent, facing the Atlantic Ocean and backed by the hinterland of the Eurasian continent. Therefore, the air in the Atlantic Ocean can penetrate deep into the interior with the westerly wind, so that all parts of the continent are affected by the ocean to varying degrees, which lays the foundation for the maritime nature of the European climate.
The North Atlantic Warm Current has a significant impact on European climate. It was originally a continuation of the Gulf Stream, flowing from the east coast of North America to the northeast to the coast of Europe. It has become an important heat source in Europe and has a very significant impact on the winter climate in Europe, making the winter temperature in western Europe much higher than the average temperature at the same latitude. , making the southwestern part of the Barents Sea located in the Arctic Circle unfrozen all year round.
The slightly triangular horizontal outline with southern Europe as the base reduces the scope affected by the cold Arctic Ocean; the seas and bays that extend deeply into the interior of the continent not only regulate the temperature in coastal areas, but also It is beneficial for the cyclone to penetrate deeper into the land and deepen the maritime nature of the European climate.
Mountains in Europe are generally not very high, and most of them are oriented close to the latitudinal direction, which does not block the airflow running from west to east. Large areas of plains are more conducive to the movement of air masses. Therefore, Europe has become the continent with the smallest arid and semi-arid areas in the world, which also determines that Europe's climate type is relatively single.
In short, Europe’s geographical location creates prerequisites for the maritime nature of Europe’s climate, while factors such as ocean currents, horizontal contours and topography play a role in promoting and deepening the maritime nature of Europe’s climate. Europe has the most extensive and typical maritime climate among all continents in the world.
(2) Circulation factors
There are four pressure systems that have the greatest impact on the weather and climate in Europe: the Azores High and Icelandic Low in the Atlantic Ocean, the Mongolian High and the South Asian Low in Asia . As the seasons change, their strengths and weaknesses wax and wane, and each plays a different role.
In winter, the Azores High retreats in the North Atlantic, affecting only the southwest corner of Europe. At the same time, the power of the Mongolian High extends westward to southeastern Europe, and together with the Azores High, forms a cross-European Continental high-pressure axis. Generally speaking, this high-pressure axis is the boundary of European winter airflow (Figure 9). To the north of the high-pressure axis, under the strong influence of the Icelandic low pressure, the isobars extend in the southwest-northeast direction, with a large pressure gradient, and westerly or southwesterly winds prevail; to the south of the high-pressure axis, due to the existence of the Mediterranean low-pressure lake, the wind direction is more complicated. Roughly to the west of the Balkan Peninsula, westerly and northwesterly winds are dominant, while to the east, easterly and northeasterly winds are dominant.
In summer, the air pressure situation is very different from that in winter (Figure 10). At this time, the Mongolian high pressure has completely disappeared, and Asia is shrouded in the South Asian low pressure system, while the Azores high pressure has been strengthened and developed, and its high pressure tongue extends to southern Europe, putting southern Europe under the control of stable anticyclonic weather; the Icelandic low pressure in summer Its power is far less than that in winter, but most parts of Europe are still affected by it. However, the westerly airflow at this time is not as stable as in winter. It only performs better south of 60° north latitude, where westerly or northwest winds often blow.
The influence is strengthened in northern Europe. Although the westerly circulation is still the basic form of atmospheric circulation in Europe, its influence is far less than that in winter. The distribution of European summer temperatures is mainly determined by radiation factors, with isotherms extending close to the latitude direction. The July 20°C isotherm passes through the northern Iberian Peninsula, southern France, the southern foothills of the Alps, the northern Hungarian plain, and goes eastward to the Southern Urals. The western section of the isotherm is slightly tilted to the south, showing the influence of the ocean on the continental temperature distribution, while the eastern section is obviously tilted to the north, indicating that the continental nature of the climate here is significantly enhanced. The average temperature in July along the Arctic Ocean is around 10°C, which is the region with the lowest summer temperature on the European continent. The summer temperature in the Mediterranean region of southern Europe is the highest, generally around 25°C, and can reach 28-29°C in some places.
In short, it can be seen from the isotherm map that there are no high-temperature areas in Europe with an average monthly temperature higher than 30°C, and there are rarely severe cold areas with an average monthly temperature lower than -20°C; winter temperatures Generally speaking, it decreases from west to east or from southwest to northeast, and the summer temperature gradually increases from north to south; the annual temperature range gradually increases from west to east, indicating that the continental nature gradually becomes stronger and the oceanic nature becomes weaker towards the east. However, even if The influence of the Atlantic Ocean on climate is also shown in the Urals. In this area, due to the influence of polar high pressure, northerly winds often blow.
The distribution and seasonal changes in air pressure in and around Europe determine the nature of the air masses operating over Europe and their impact on Europe's weather and climate.
The air masses operating over Europe can be divided into three types: polar air masses, icy air masses and tropical air masses. Each type can be divided into oceanic or continental types according to whether the source is over the ocean or continent.
The ice-ocean front formed by the intersection of icy ocean air masses and polar air masses (mainly polar ocean air masses) is most obvious in winter and has a great influence on the weather and climate in Northern Europe. Polar air masses and tropical air masses form the polar front. The polar front in Europe is divided into two branches: the northern branch is mainly formed by polar oceanic air masses and tropical oceanic air masses. It is located on the ocean near the British Isles. It is located southward in winter and northward in summer; A branch forms over the Mediterranean, called the Mediterranean front, which is mainly the interface between polar continental air masses and tropical continental air masses. Since southern Europe is controlled by subtropical anticyclones in summer, the Mediterranean front only appears in winter and disappears in summer.
Air mass movement is often related to frontal and cyclone activity. Cyclone activity in Europe is at its peak in winter, and its range of activities covers the entire Europe from Iceland in the north to the Mediterranean in the south. Among them, the northern polar front cyclone has the most profound impact on Europe. It affects the exchange of heat and moisture between the Atlantic Ocean and the European continent. plays a prominent role. In summer, as the Icelandic low pressure weakens and the pressure gradient decreases, the frequency of cyclone activity decreases.
3. Distribution characteristics of temperature and precipitation
(1) Temperature
As can be seen from the isotherm maps in January and July, the distribution of temperature in Europe As a rule, winter is very different from summer. As far as the entire continent is concerned, circulation factors dominate in winter; radiation factors dominate in summer.
1. Winter temperature distribution characteristics In winter, due to the strong low pressure in Iceland, frequent cyclone activity, and large-scale heat exchange between the Atlantic Ocean and the European continent, most parts of Europe are relatively mild. According to research, it is called Europe The heat source of the North Atlantic Warm Current brings heat to the British Isles and Scandinavia every year, which is equivalent to one-third to one-half of the total solar radiation received by these areas every year. Therefore, despite the latitude of these areas It is quite high, but the temperature in winter is not low.
The January 0°C isotherm in Europe generally follows the western coast of Scandinavia southward to the western end of the Alps, passes through the Po River plain, the western and southern Balkans, and ends on the southern coast of the Crimean Peninsula. . This isotherm divides Europe into cold and warm parts. Western and Southern Europe generally have mild winters, with temperatures generally above 0°C. The January 5°C isotherm passes along the western British Isles and the west coast of France. Evergreens can already grow west of this line. The average temperature in January in most parts of southern Europe is above 5°C, and can reach 12-13°C in some places. Only the central and northern parts of the Balkan Peninsula have lower temperatures. In the eastern part of Northern Europe, Eastern Europe, and Central Europe, the role of polar continental air masses increases, and ice ocean air masses often invade, making winters relatively cold.
The average January temperature in the northern Urals drops to about -20°C, which is the lowest monthly average temperature in Europe. Although it is severely cold, it can be called "mild" compared with Asia.
Winter temperatures in most parts of Europe show positive anomalies, that is, they are higher than the average temperature at the same latitude. Generally, the number of positive anomalies in the northern region is higher than that in the southern region. The average January temperature in western Scandinavia is more than 20°C higher than the average temperature at the same latitude, which is unique among the world's continents.
2. Summer temperature distribution characteristics In summer, due to the weakening of the Icelandic low pressure and the Azores high pressure covering southern Europe, the polar high pressure has less impact on Europe.
(2) Precipitation
1. Distribution pattern of precipitation areas In the western half of Europe, except for the northern part of Northern Europe and the southeastern part of the Iberian Peninsula in Southern Europe, precipitation is generally more. This area with heavy rainfall extends in a wedge shape toward Eastern Europe, reaching the central and southern parts of the Ural Mountains (Figure 13).
The distribution of precipitation in Europe clearly reflects the role of circulation factors. Atlantic air masses rich in water vapor, especially tropical Atlantic air masses, bring a large amount of water vapor to the land as the cyclones move from west to east. The further west, the more precipitation occurs. To the east, the cyclone intensity weakens, the frequency decreases, and the precipitation also increases. decrease. The role of the ice-ocean front in northern Europe increases. Due to the low water vapor content in the atmosphere, precipitation is generally not large. Southern Eastern Europe is affected by the high pressure axis of the Eurasian continent, with low cyclone frequency and low precipitation. The Iberian rainless area is related to the local high pressure.
It can be seen that the regional distribution of precipitation in Europe changes from west to east, and there are also zonal differences. The influence of terrain makes this law more complicated. Mountains always receive more precipitation than the plains adjacent to them, and windward slopes receive more precipitation than leeward slopes. Southern Iceland, the west of Scandinavia, the British Isles and the Iberian Peninsula, the outside of the Alps, and the west of the Apennines and Dinaric Alps are areas with more precipitation in Europe, generally under 1000 mm. Above, some locations have even recorded annual precipitation of more than 5,000 mm. The interior of Scandinavia, the southeast of the Iberian Peninsula, the southeast of the Eastern European Plain, and the coastal areas of the Arctic Ocean are areas with less precipitation in Europe. The annual precipitation is less than 400 mm, and in some areas it is less than 200 mm. Precipitation in high mountain areas is vertically zonal.
2. Precipitation types In winter, snowy weather can be encountered all over Europe (even southern Europe), except for areas north and east of the line from the northern Caspian Sea to southern Scandinavia. Outside the region, the solid precipitation in other regions accounts for less than 30% of the annual precipitation, and the snowfall in the British Isles, western France and southern Europe is less than one-tenth of the annual precipitation (Figure 14).
3. Seasonal distribution of precipitation. Most parts of Europe have precipitation throughout the year. There is no obvious difference between dry and wet seasons. However, it can still be divided into evenly distributed precipitation throughout the year, mainly summer precipitation and winter precipitation. Precipitation mainly occurs in three areas. In Western Europe and the western part of Northern Europe, precipitation is almost evenly distributed throughout the year. In the winter half of the year, there is slightly more precipitation due to frequent cyclone activity. In the eastern part of Northern Europe, Central Europe, and Eastern Europe, due to the enhanced continental nature, the maximum precipitation occurs in the summer months; in Southern Europe, due to winter Affected by the polar front and the cyclonic activity of the Mediterranean front, precipitation is mainly in winter, and this trend becomes more obvious toward the south. In summer, there is very little precipitation due to the control of anticyclones.
Europe can be divided into the following six climate types.
(1) Polar ice sheet climate zone
Ice sheet climate is only found on various islands in the Arctic Ocean. It is controlled by icy air masses all year round, and the temperature is very low. The average temperature in the hottest month is around 0°C, and the annual precipitation is around 200 mm. In the western part of the Spitsbergen Islands, due to the influence of the North Atlantic warm current, the climate is slightly milder. The average temperature in the hottest month can reach about 5℃, and the precipitation can reach 300 mm.
(2) Polar tundra climate zone (polar long-cold climate zone)
This zone includes Iceland and the northern edge of the European continent. The temperature here is low throughout the year, and the landscape belongs to the tundra zone and forest tundra zone.
Winter temperatures are higher in the west than in the east. The average temperature of the coldest month in the coastal areas of Iceland is around 0°C. The average temperature in January in the coastal areas of Murmansk is around -0.5°C, while in the Kanin-Pechora region in the east it drops to -20°C. Around ℃. The temperature in summer is generally around 10°C, the growing season is very short, only 2-2.5 months, and there are often frosts even in summer. Therefore, the climate conditions are very unfavorable for agriculture. There is almost no farming and livestock raising (mainly deer raising). industry) is the main agricultural sector here.
(3) Subarctic coniferous forest climate zone (subarctic continental climate zone)
This area includes most of Fennoscandia and the northern part of the Eastern European Plain . Due to its high latitude, winters are long but rarely severe, and summers are short and cool. The western coast of Scandinavia is controlled by polar ocean air masses throughout the year and has an oceanic climate. The temperature in winter is around 0°C and there is abundant precipitation. East of the Scandinavian Mountains to the Urals, the role of polar continental air masses and glacial air masses increases, and the climate transitions to continental, with cold winters and temperatures decreasing from west to east. The average temperature in Gavle in January is - 4.4℃, Petrozavodsk -9.9℃, and Perm dropped to -15.4℃. Whenever icy air masses invade, severe cold temperatures of -30°C and -40°C often occur. Summer is generally cool, with the average temperature in July being 10-12°C in the north and 16-18°C in the south. The growing season is not long, usually 3-4 months. The duration of the growth temperature (above 10°C) suitable for rye, flax, vegetables, etc. in Eastern Europe is only 90 days at most, so agriculture is not developed here.
The precipitation here is mainly related to cyclones. The annual precipitation on the western coast is more than 1,000 mm, and in other areas it is 500-800 mm. The seasonal distribution of precipitation is relatively uniform along the western coast, with slightly more precipitation in winter and gradually changing to more precipitation in summer in the east. In addition to cyclonic precipitation, convective rain also accounts for a certain proportion.
(4) Temperate maritime climate zone
This zone includes the British Isles, France and the west of Central Europe, as well as southern Scandinavia and the Iberian Peninsula. Open bay coastal area. The air pressure here throughout the year is high in the south and low in the north, with westerly winds and a strong influence from the Atlantic air mass. Mild winters, cool summers, small annual temperature ranges, more rainy days and less sunshine are the climate characteristics of this area.
The average temperature in this area in January is above 0℃. Rivers generally do not freeze. There is not much snowfall, there is generally no snow in the west, and the snow cover in the east rarely lasts longer than a week. However, when the Mongolian high pressure is strong and the polar continental air mass from the east invades, it often leads to catastrophic cold weather. Summer temperatures are generally not high. The average July temperature in the British Isles is 12-17°C, and in the mainland part it is 15-22°C. The temperature is lower in the north and higher in the south.
Western Europe has frequent cyclone activity and heavy rainfall. The annual rainfall in the western part of the British Isles is more than 1,000 mm, and the annual rainfall along the western coast of Scotland can reach 2,000 mm or more. In other areas, it is mostly between 600-1000 mm. The seasonal distribution of precipitation is relatively even, with slightly more precipitation in autumn and winter in the west and slightly more in summer in the east. For example, Dublin accounts for 26% in autumn and winter, and 24% in spring and summer; Cologne accounts for 31% in summer, 25% in autumn, 23% in winter, and 21% in spring.
(5) Temperate continental climate zone
This zone includes two climate types: temperate continental humid climate and temperate continental semi-arid and arid climate. Generally speaking, eastern Central Europe and Eastern Europe Central China belongs to the former, and southern Eastern Europe belongs to the latter.
The climate in eastern Central Europe transitions from oceanic to continental. The influence of polar ocean air masses dominates here all year round, with mild winters and low summer temperatures. The average temperature in January is generally 0-4℃, and can reach -5℃ in a few areas. The average temperature in July is generally around 18℃. In a few areas it can exceed 20℃. However, ice ocean air masses and polar continental air masses also often invade, so the weather is very unstable. Precipitation is greatly affected by terrain. It is generally 500-600 mm in plain areas and more in summer.
The climate in Eastern Europe is divided into two regions: north and south.
The mixed forest zone in the central part is the northern zone, which has a humid continental climate. It is greatly affected by polar ocean air masses. There is no severe cold in winter and the temperature in summer is not too high. The average temperature in most areas in January is between -5 and 14 degrees Celsius. The average temperature in July does not exceed 20℃, and the annual precipitation is generally 500-600 mm, even more in some areas. The southern zone is located in the Eurasian high-pressure axis (the Soviets called it the "Voyekov high-pressure axis") and the area south of this high-pressure axis. Here, the westerly airflow and related cyclone activities have significantly weakened, anticyclonic weather has increased, and annual precipitation has increased. It is generally 300-500 mm, 200 mm or less in the southeast, and the summer temperature is between 20-25°C. The water balance of the entire southern region is negative, and it has a temperate continental semi-arid and arid climate. Most of the natural landscape is grassland, and the southeast is semi-desert or desert. The southern region is rich in heat resources and fertile land, and is a major agricultural area. However, due to insufficient precipitation and high variability, droughts often occur.
(6) Mediterranean climate zone
This zone includes most of the Iberian Peninsula, the French Mediterranean coast, the Apennine Peninsula, most of the Balkan Peninsula and various areas scattered in the Mediterranean. islands. Mild and rainy winters and hot and dry summers are the main characteristics of this region's climate.
Mediterranean climate is a unique climate type on the west coast of the subtropical continent. Its formation is related to changes in air pressure conditions in winter and summer and the movement of wind belts. The latitude of the Mediterranean region happens to be the transition zone of atmospheric circulation; to the north is the westerly belt and to the south is the trade wind belt. In summer, the subtropical high moves northward. Under the control of the Azores high, the Mediterranean region has sunny, dry and drier weather, with average weather in July. The temperature reaches 24-28°C, and the highest temperature can reach 40°C. In winter, the subtropical high pressure belt moves southward, and the Azores high pressure retreats to the Atlantic Ocean. The Mediterranean region is affected by westerly winds, with frequent cyclone activity, more precipitation, and a mild climate. In January The average temperature is generally above 5℃, and can reach 12℃ in a few areas.
The existence of the Mediterranean Sea itself also plays a large role in the formation of the Mediterranean climate. Due to the large area of ??the Mediterranean, a low-pressure lake forms in the Mediterranean area in winter, which is conducive to the formation of the Mediterranean front, thereby generating a series of cyclones, making the weather in the Mediterranean area particularly mild and rainy. At the same time, the higher Mediterranean water temperature also makes the coastal areas more temperate. In summer, on the contrary, the temperature on the Mediterranean is lower than that on the European continent, and the air pressure is relatively high, which strengthens the Azores high, making the Mediterranean area very hot and dry. In this way, the most typical subtropical climate in the world is formed in the Mediterranean region with warm rains in winter and hot and dry summers. Therefore, it is called "Mediterranean climate".
In the mountainous areas of the above-mentioned climate zones, the climate is relatively complex. Due to the different heights, cutting conditions and slope directions of the mountains, the climate changes greatly within a short distance. Higher up the mountain, there are vertical changes in climate.