Why is it cool in winter and hot in summer?

Causes and conditions of climate formation: (1) Low latitude climate Low latitude climate is mainly controlled by equatorial air mass and tropical air mass. The main circulation systems that affect the climate are equatorial convergence zone, Wacker circulation, trade winds, equatorial westerly winds, tropical cyclones and subtropical high. The annual radiation difference of the ground-air system is too large, so the annual temperature is high. The average temperature in Leng Yue is above 15 ~ 18℃, and the annual evapotranspiration may be above 130cm. This area can be divided into five climate types, among which tropical arid and semi-arid climate types can be divided into three subtypes. 1. The equatorial rainy climate is distributed in the equator and its north and south 5 ~10, with different widths, mainly distributed in Zaire River basin in Africa, Amazon River basin in South America and Sumatra Island to Irian Island between Asia and Oceania. The sun is high at noon all year round, so there is no winter in summer. The monthly average temperature is 25-28℃, and the annual average temperature is about 26℃. The annual temperature difference is generally less than 3℃, and the daily temperature difference can reach 6 ~ 12℃. Because it is controlled by equatorial air mass all the year round, the wind is weak, mainly convergent updraft, and there are many thunderstorms. Therefore, it is rainy all year round, and there is no dry season. The annual precipitation is above 2000mm, and the monthly precipitation is at least 60 mm However, the annual precipitation changes greatly, which is related to the position change of equatorial convergence zone. 2. Tropical maritime climate, distributed in the trade winds along the east coast of the mainland and several islands in the tropical ocean, latitude 10 ~ 25. Here is the windward coast, where tropical marine air masses prevail all the year round and the climate is maritime. The average temperature in the hottest month is around 28℃, and that in Leng Yue is between 18 ~ 25℃, and the annual range and diurnal temperature range is small. Because the east wind (trade wind) brings hot and humid ocean air mass, there are many topographic precipitation besides convective rain and tropical cyclone rain, and the precipitation is abundant. The annual precipitation is above 1000mm, generally concentrated from May to 10, with no obvious change. 3. The tropical climate in dry season and rainy season is roughly distributed between 5 and 25 in the northern and southern hemispheres. When the sun is low at noon, it is located under the trade winds and controlled by the tropical continental air mass. This is a dry season that flows downwards. At noon, when the sun is too high, the equatorial convergence zone moves and there is a moist convergence updraft, which is the rainy season. At least 1 ~ 2 months in a year is the dry season. Evapotranspiration in wet season is less than precipitation. The annual precipitation is about 750 ~ 1600 mm, and the precipitation variability is very large. The annual temperature is high, and the average temperature in Leng Yue is above 16 ~ 18℃. The end of the dry season, before the arrival of the rainy season, the highest temperature, is a hot season. 4. Tropical monsoon climate is distributed in the southeast of Asian continent from north latitude 10 to the tropic of cancer, such as the south of Taiwan Province Province, Leizhou Peninsula and Hainan Island, Indochina Peninsula, most of Indian Peninsula, the Philippines and the northern coast of Australia. The tropical monsoon is developed here, and the wind direction changes obviously seasonally throughout the year. Controlled by tropical continental air mass, precipitation is scarce. When the equatorial air mass is controlled, there is abundant precipitation, tropical cyclone rain and annual precipitation, which is generally in 1500 ~ 2000 mm and concentrated in June ~10 (northern hemisphere). High temperature throughout the year, the annual average temperature is above 20℃, the annual range is about 3 ~ 10℃, and the spring and autumn are extremely short. 5. The tropical arid and semi-arid climate is distributed in the continental center and western coast of subtropics and trade winds. In the southern hemisphere and the northern hemisphere, it extends north and south around the Tropic of Cancer, and the average position is roughly between latitude 15 ~ 25. Due to the different drought degree and climate characteristics, it can be divided into three subtypes: tropical arid climate (5a), tropical foggy arid climate (5b) and tropical semi-arid climate (5c). 5a and 5c are the sources of tropical continental air masses, and the annual and daily variation ranges of temperature and extreme maximum temperature are very large. During the five years, it was controlled by the subtropical high downward flow, with little precipitation. 5c is located at the outer edge of 5a, which is controlled by subtropical high for half a year, and it is dry with little rain. In the season when the sun is high, the equatorial trough moves and there is convective rain, so there is a short rainy season. 5b is located on the west coast of tropical continent, where cold ocean currents pass. Affected by subtropical high downflow all the year round. It is foggy and rainy, with little precipitation, but the temperature is cool, and the annual range and diurnal range of the temperature is small. (2) Mid-latitude climate This is the area where tropical air mass and polar air mass compete with each other. The main circulation systems affecting climate are polar front, prevailing westerly wind, extratropical cyclone and anticyclone, subtropical high and tropical cyclone. The radiation energy balance in this area changes greatly in one year, so the four seasons are distinct. The average temperature in Leng Yue is below 15 ~ 18℃ and above 10℃ in April ~/February. The annual potential evapotranspiration is between130 and 52.5 cm. The non-periodic change of weather and the seasonal change of precipitation are significant. In addition, the mid-latitude belt in the northern hemisphere has a large continental area, which is influenced by the thermal contrast between land and sea and the towering terrain, making the climate in this area more complicated. There are 8 climate types in this area. 6. The subtropical arid and semi-arid climate is distributed on the high latitude side of the tropical arid climate, about on the west coast of the mainland and the inland area with latitude of 25 ~ 35. It is formed under the action of subtropical high downwind and the back shore wind of trade winds. Due to the different degree of drought, it can be divided into two subtypes: arid 6a and semi-arid 6b. 6a Subtropical arid climate is characterized by partly cloudy, little rain, strong sunshine and extremely high temperature in summer. However, the cold season temperature is lower than that of type 5a, and the annual temperature is higher than that of type 5a, reaching above 20℃. There is a small amount of cyclone rain in cool season, and the soil water storage capacity is slightly larger than that of 5a type. 6b Subtropical and semi-arid climate, located at the outer edge of area 6a. The summer temperature is lower than that of type 6a, and the winter precipitation is slightly higher than that of type 6a. 7. The subtropical monsoon climate is distributed on the east coast of subtropical Eurasia, centering around 30 N, and extending about 5 to the north and south respectively. This is an area where tropical marine air mass and polar continental air mass compete with each other. It is affected by tropical cyclone activity in summer and autumn, with hot and humid summer and dry winter. The average temperature in the hottest month is above 22℃, the average temperature in Leng Yue is about 0 ~ 15℃, and the annual temperature is about 15 ~ 25℃. The precipitation is above 750 ~ 1000 mm. Summer rain is concentrated, and there is no obvious dry season. The four seasons are distinct and the frost-free period is long. 8. The subtropical humid climate is distributed in the subtropical east coast of North and South America, Africa and Australia, with latitude of 20 ~ 35. In winter, it is influenced by the polar continental air mass, and in summer, it is controlled by the moist marine air mass flowing in the western edge of the ocean high. Because the mainland is small, there is no monsoon climate. The temperature difference between winter and summer is smaller than that in monsoon region, and the seasonal distribution of precipitation is more uniform than that in monsoon region. 9. The subtropical dry summer climate (Mediterranean climate) is distributed in the zone between 30 and 40 on the west coast of the subtropical continent. Affected by the seasonal movement of subtropical high, it is located in the center of subtropical high or its eastern edge in summer, with sinking airflow, dry and rainy weather and strong sunshine. In winter, the subtropical high moves to the low latitude, which is controlled by the westerlies. Frontal and cyclone activities are frequent, bringing a lot of precipitation. The annual precipitation is about 300 ~1000 mm. It is warmer in winter, and the average temperature in Leng Yue is about 4 ~ 10℃. Due to the different temperatures in summer, it is divided into two subtypes. Cool in summer, close to the coast of cold ocean current, cool and foggy in summer with little rain. The average temperature in the hottest month is below 22℃, and that in Leng Yue is above 10℃. 9b Warm summer type, far from the coast, dry and hot in summer, the average temperature in the hottest month is above 22℃, the winter is mild and humid, and the temperature is slightly higher in the year. 10. The temperate maritime climate is distributed in the zone of about 40 ~ 60 on the west coast of temperate continent. The west wind prevails here all the year round, controlled by temperate ocean air mass, and there is a warm current passing along the coast. It is warm in winter and cool in summer. The average temperature in Leng Yue is above 0℃, the average temperature in the hottest month is below 22℃, and the annual temperature difference is small, about 6 ~ 14℃. It is wet and rainy all year round and rainy in winter. The annual precipitation is about 750 ~ 1000 mm, and it can reach more than 2000mm in the windward mountainous area. 1 1. The temperate monsoon climate is distributed on the east coast of Eurasia at about 35 ~ 55. The north wind often blows here in winter, and the weather is cold and dry. The average temperature in Leng Yue is below 0℃, with great difference between north and south. Southeast winds prevail in summer, which is warm and humid. The average temperature in the hottest month is above 20℃, and the temperature difference between north and south is small. The annual temperature is relatively high, the annual precipitation is concentrated in summer, and the distribution of precipitation decreases from south to north and from coastal to inland. The aperiodic change of weather is remarkable. When a cold wave breaks out in winter, the temperature can drop 10℃ or even 20℃ within 24 hours. 12. the temperate continental humid climate is distributed in the eastern part of the temperate maritime climate zone of Eurasia and the temperate zone east of North America100 W. Winter is controlled by polar continental air mass and cold, with a small amount of cyclone precipitation. In summer, due to the invasion of tropical ocean air mass, there is more precipitation, but it is not as highly concentrated as the monsoon region. There are four distinct seasons here, and the weather changes dramatically. 13. The temperate arid and semi-arid climate is distributed in central Asia and North America, with 35 ~ 50 north latitude ... Because it is far away from the ocean or protected by mountains, it is not affected by marine air masses and controlled by continental air masses all the year round, the climate is dry, hot in summer and cold in winter, and the temperature is very high throughout the year. Due to different degrees of drought, it can be divided into two subtypes: temperate arid climate (13a) and temperate semi-arid climate (13b). 3) High-latitude climate Polar air mass and glacier air mass prevail in high-latitude climate areas. There is cyclone activity in front of the glacier. The radiation difference of the earth-atmosphere system here is negative, so the temperature is low and there is no real summer. The water vapor content in the air is low and the precipitation is low, but the evaporation is weak, and the annual evapotranspiration may be less than 52.5cm. This zone can be divided into three climate types. 14. the subtropical continental climate is distributed in the area of 50 N or 55 N to 65 n. the possible annual evapotranspiration here is between 35 cm and 52.5 cm. Winter is very long, and it is winter for at least 9 months in a year. In winter, the night time is long, and the height of the sun is small at noon. It is also the center of cold and high pressure in the central and eastern Eurasia. The wind is light, the clouds are few, the ground radiation cools down strongly, the land is the strongest, and the temperature in winter is extremely low. The days in summer are long, the average temperature in July is above 15℃, and the annual temperature is extremely high. There is little precipitation throughout the year, mainly in the warm season. There is little snow in winter, but evaporation is weak and melting is slow. There is snow for 5 ~ 7 months every year, and the thickness of snow is about 600 ~ 700 mm, so the soil freezing phenomenon is serious. Due to the moderate temperature, there is some precipitation in warm season, which is suitable for coniferous forest growth. 15. The climate of polar tundra is distributed in the northern edge of North America and Eurasia, part of the coast of Greenland and several islands in the Arctic Ocean. In the southern hemisphere, it is distributed in Malvinas Islands (Falkland Islands), south shetland islands and South Orkney Islands. The possible annual evapotranspiration is less than 35 cm. It is winter all year round, and the average monthly temperature in a year is about 0℃ ~ 14 months. Its latitude is close to or within the polar circle, so the extreme phenomenon of day and night is obvious. The temperature is very low at night, but the adjacent ocean is slightly higher than the subtropical continental climate. The average temperature in Leng Yue is between minus 20 and 40 degrees. The average temperature in the hottest month is about 1 ~ 5℃. In July and August, the temperature can still drop below 0℃ at night. There is some precipitation in front of the glacier, with an average annual precipitation of about 200 ~ 300 mm, less than 200 mm in inland areas, mostly dry snow, with rain or wet snow in warm seasons. Due to the high wind speed, snow fog often forms, the visibility is not good, and the snow area on the ground is not large. Natural vegetation only includes mosses, lichens and small shrubs, which constitute the tundra landscape. 16. The climate of polar ice sheet is distributed in Greenland, Antarctic continent and several islands in the Arctic Ocean. It is the source of the ice ocean air mass and the Antarctic air mass. It is cold all year round, with the monthly average temperature below 0℃ and the lowest annual average temperature in the world. There is a long period of extreme day and night in a year. The annual precipitation is less than 250 mm, which is dry snow and will not melt, forming a thick ice sheet for a long time. Long-term gale, cold wind with snow, poor visibility. 4) Plateau climate changes with the increase of altitude, which leads to obvious vertical zonality of alpine climate. In order to distinguish the climate affected by altitude and latitude, and because the alpine climate is limited to a local area, the plateau climate is classified as a large category and is not included in the lowland classification system. Alpine climate has obvious vertical zonality, which varies with latitude and regional climate conditions. Its characteristics are as follows: (1) The differentiation of vertical climatic zones in mountainous areas varies with latitude and the mountain itself. In low latitude mountainous areas, the foothills belong to equatorial or tropical climate. With the increase of altitude, the surface heat and water conditions change gradually, and vertical climatic zones appear alternately. This change is similar to the change of lowlands with the increase of latitude. The higher the latitude of the mountain, the smaller the differentiation of the vertical climate zone. The difference of altitude in mountainous areas is small, and the differentiation of vertical climate zone is small. 2) The vertical climate zone in mountainous areas has the "brand" of local climate types. For example, the equatorial mountain area has the characteristics of no obvious change from the foothills to the top of the mountain all year round. Both Mount Everest and Changbai Mountain have monsoon climate characteristics. (3) The differentiation of mountain vertical climate in humid climate zone is mainly determined by heat conditions, while the differentiation of mountain vertical climate in arid and semi-arid climate zone is closely related to heat and humid conditions. The dryness in this area is greater at the foot of the mountain, and gradually decreases with the elevation. (4) In the same mountainous area, due to the different local conditions such as slope direction, slope, topographic relief, concave and convex, looming, the vertical change of climate is also different, such as the warm zone on the hillside and the cold lake in the valley. There is indeed a change in the climate in mountainous areas. (5) Vertical climatic zones in mountainous areas have different origins and characteristics from horizontal climatic zones with different latitudes.

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