Warm weather in yellow summer

1, characteristics and causes of temperature distribution in winter and summer

Causes of seasonal distribution characteristics

In winter, it is 65438+ 10 month, which is warm in the south and cold in the north, with a large temperature difference between the north and the south. Mohe is the coldest place in China in winter. The 0℃ isotherm roughly passes through the eastern margin of the Qinghai-Tibet Plateau and reaches the Qinling-Huaihe line eastward. China has a large latitude, and the sun shines directly in the southern hemisphere in winter. The higher the latitude, the shorter the day and the lower the height of the sun at noon, so the heat gained in the north is much less than that in the south and the temperature is much lower.

(2) The north is close to the source of the winter wind, which is deeply influenced by the winter wind and aggravates the cold in the north. The farther south, the winter wind is blocked by mountains, its power and frequency are greatly weakened, and the temperature difference between north and south is increased (which can be compared with the influence of North American topography on climate)

In summer and July, except for the Qinghai-Tibet Plateau, Tianshan Mountains and Daxinganling Mountains, the temperature in the whole country is generally high, and the temperature difference between north and south is small. Turpan Basin is the hottest place in China in summer. The sun shines directly in the northern hemisphere. Although the sun is still higher in the south than in the north, the days in the north are longer than in the south. There is little difference between the exposure time of the sun and the solar heat obtained from the north and the south.

② Affected by the summer monsoon, there are many sunny days in the north, and the temperature rises quickly, while the rainy season in the south is long and rainy, and the sunshine time is short.

The low temperature in mountainous areas such as the Qinghai-Tibet Plateau is due to the high terrain.

Turpan basin is the hottest in summer, because: ① the topography of the basin is not easy to dissipate heat, and when the external airflow sinks over the mountainous area, it has a strong warming effect and forms a foehn; ② Deserts are widely distributed and absorb heat quickly; ③ The air is dry, the sky is partly cloudy and the solar radiation is strong.

2. Division and distribution of temperature zones

According to the accumulated temperature ≥ 10℃, China can be divided into five temperature zones from north to south, namely, cold temperate zone, middle temperate zone, warm temperate zone, subtropical zone and tropical zone, as well as the unique climate zone of Qinghai-Tibet Plateau.

Temperature range ≥ 1000℃ accumulated temperature crops mature.

Tropical Qiong is an important tropical crop and tropical economic forest producing area in China. The temperatures in southern Taiwan Province, southern Guangdong (Leizhou Peninsula) and southern Yunnan (Xishuangbanna) are all above 8000℃.

In most areas south of the subtropical Qinhuai line and east of the Qinghai-Tibet Plateau, the temperature of 4500-8000℃ is two or three crops a year. Double cropping system of rice and wheat. Double cropping rice and winter rape or winter wheat. China is an important producing area of rice, rape, subtropical fruit and economic forest.

In most areas of the middle and lower reaches of the Yellow River in warm temperate zone, that is, the whole of Shandong, most of Shaanxi, Shanxi, Hebei and southern Xinjiang, the temperature is 3400-4500℃ for three crops in two years or two crops in one year. Winter table, corn, millet and temperate fruits (apples, pears, grapes, etc.) are the main producing areas. ) In China.

Mid-temperate Kyrgyzstan is harvested once a year in Heilongjiang, Liaoning, most parts of Inner Mongolia and northern Xinjiang at 1600-3400℃. Spring wheat, soybean, beet, corn, millet, sorghum

It is harvested once a year in the cold temperate zone and the northernmost part of Inner Mongolia < 1600℃. The early-maturing crops with short growth period are mainly spring wheat, barley and potato.

Qinghai, most of Tibet and western Sichuan in plateau climate area are harvested once a year at < 2000℃. Highland barley, etc

3. The laws and reasons of precipitation distribution and time allocation.

The basic characteristics (laws) have an impact.

Name content

The spatial distribution law gradually decreases from the southeast coast to the northwest inland, and the main source affecting precipitation in China is the summer monsoon. The vast areas in eastern China are greatly influenced by the southeast monsoon and southwest monsoon, with more precipitation; The northwest inland area is not obviously affected by the summer monsoon, and the precipitation is scarce. The southeast is humid, and the farther inland, the drier it is.

Time changes, seasonal changes, uneven distribution of precipitation, precipitation concentrated in May-September summer, autumn, Xia San season, affected by humid air from the ocean, abundant precipitation; In winter, due to the influence of dry air in mainland China, less precipitation causes frequent droughts and floods in China, with strong or early summer monsoon, flooding in the north and drought in the south. The summer monsoon is weak or late, with waterlogging in the south and drought in the north.

The interannual variation of precipitation in various places is great, and the south is smaller than the north, which is caused by the anomaly of the maximum advance and retreat law of summer monsoon in the arid area of northwest China

North-south difference of precipitation: less precipitation and short rainy season; South: There is a lot of precipitation and a long rainy season, which is determined by the advance and retreat law of the frontal rain belt formed by the summer monsoon. Form a spring drought and summer flood in the north; Meiyu and Summer Drought in Jianghuai Area

[Note] There are three important dividing lines about the distribution of precipitation: a.800mm annual precipitation line, which roughly passes through the southeast edge of the Qinghai-Tibet Plateau and then turns eastward along the Qinling-Huaihe line. The annual precipitation in the east and south of the line is above 800mm, which is a warm area. It is the main paddy field operation area in China, with rice production as the main agriculture. North of this line is a semi-humid area, mainly dry farming; B: The annual precipitation line is b:400mm, roughly along the Daxinganling-Great Wall line to Lanzhou, to the southwest, and to Gangdise Mountain via the Qinghai-Tibet Plateau. This line is the general dividing line between semi-humid area and semi-arid area in China, and it is also the dividing line between agricultural area and animal husbandry area in China. C:200mm annual precipitation line: it passes through central Inner Mongolia-Helan Mountain-Qilian Mountain and Qinghai-Tibet Plateau. This line is roughly the dividing line between semi-arid and arid areas in China. Most areas with annual precipitation below 200 mm are desert areas. In addition to the oasis with irrigation water, the natural environment is harsh, sparsely populated and very desolate.

4. The law of rain belt in China and its influence.

(1) Formation of frontal rain belt: When summer monsoon warm and humid airflow landed northward, it met with winter cold and dry airflow from north to south, and the lighter warm and humid airflow was lifted above the cold air. During the rising process of warm and humid airflow, the temperature drops continuously, and condensation leads to rainfall, forming frontal rain, thus a frontal rain belt with more precipitation appears at the intersection of cold and warm airflow in eastern China.

⑵ Movement of front rain belt: In May, rain belt lingered in Nanling area; In June, after the rain belt moved to the Yangtze River basin, it swayed between the Yangtze River and Huaihe River for about a month (Meiyu); At the beginning of July, the rain belt began to move north and west, and reached North China and Northeast China in July and August. (In June, July and August, the southwest and Guangdong provinces are also affected by the southwest monsoon. )

Note: The boundary between shadow and non-shadow in the figure is the boundary between monsoon area and non-monsoon area in China;

Daxinganling-Yinshan-Helan Mountain-Bayankala-Gangdise Mountain Line

【 Note 】 In addition to the advance and retreat of the summer monsoon and the frontal rain caused by it, topography and typhoons are also factors affecting precipitation in China. For example, Huoshaoliao, the place with the most precipitation in China, is located on the windward slope of the valley facing the southeast monsoon; Turpan-Toksun, which has the least precipitation in China, is located in the deep inland basin with closed terrain and little precipitation. In addition, in summer and autumn, typhoons that affect the southeast coast of China often bring a lot of precipitation.

5. Division and distribution of dry and wet areas

According to the relationship between precipitation and evaporation, there are humid areas, semi-humid areas, semi-arid areas and arid areas in China from southeast to northwest.

The dry and wet conditions in dry and wet areas are mainly distributed in regional climate and vegetation.

Wet area > 800 mm

Precipitation is greater than evaporation in most parts of the southeast, and there is humid climate and forest in the northeast.

Semi-humid area 400-800 mm

Precipitation > Evaporation Northeast Plain, North China Plain, South Loess Plateau and Southeast Qinghai-Tibet Plateau have humid climate with grasslands and forests.

Semi-arid area 200-400 mm

precipitation