The climate of China.

1973, Zhu Kezhen put forward the basic situation of periodic climate fluctuation in China. He believes that in the past 2000a years, the Han Dynasty was a warm period, and soon after the Three Kingdoms began, the climate became cold, which delayed the beginning of the Tang Dynasty. After the end of the Tang Dynasty, the climate became cold again, and gradually entered the Little Ice Age in the15th century, showing a structure of two peaks and three valleys, until the climate became warmer in the early 20th century and the Little Ice Age ended. The Han Dynasty and the Tang Dynasty were warm periods when the annual average temperature was about 2℃ higher than that of modern times. The research results have been widely used in climatology and historical geography. But in recent years, due to the discovery of new materials and the improvement of research methods, many scholars have supplemented Zhu Kezhen's work. Among them, Zhu and others believe that since 2000 ~ 3000, the climate change in China has gone through the following stages: ① the cold and dry climate in the Western Zhou Dynasty (BC 165438 to the middle of the 8th century BC); ② Warm and humid climate from the Spring and Autumn Period to the early Western Han Dynasty (from the middle of the 8th century BC to BC 1 century BC); ③ The cool and dry climate from the late Western Han Dynasty to the Northern Dynasty (65438 BC+the middle of the 0 th century to the 6 th century); ④ Warm and humid climate in Sui and pre-Tang period (7th-8th century); ⑤ The cool and dry climate from the late Tang Dynasty to the Northern Song Dynasty (9- 1 1 century); ⑥ The dry and wet climate in the early Jin Dynasty (12nd century); ⑦ The cool and dry climate at the end of Jin and the beginning of Yuan (13 and the first half of 65438+4th century); ⑧ During the Ming and Qing Dynasties (1the second half of the 4th century to the beginning of the 20th century), the climate was cold and dry. Later, many geographers made further modifications to the climate change in China, but the general trend is this.

In the historical period, the climate not only fluctuates periodically in temperature, causing temperature changes, but also changes in humidity. Generally speaking, warm period and wet period, cold period and dry period are corresponding, but each cold and warm period has wet and dry fluctuations, which cannot be generalized. Zhu and others believe that the change of temperature is faster than that of precipitation, and the change of precipitation is greater than that of temperature. In the historical period, there is obvious correlation between climate fluctuation and dry and wet fluctuation, but they are not completely synchronized. Characteristics of Climate Change in China since 2000

1973, Zhu Kezhen put forward the basic situation of periodic climate fluctuation in China. He thought that the Han Dynasty was a warm period, and soon after the Three Kingdoms began, the climate became cold, which was postponed until the Tang Dynasty. After the end of the Tang Dynasty, the climate became cold again, and gradually entered the Little Ice Age in the15th century, showing a structure of two peaks and three valleys, until the climate became warmer in the early 20th century and the Little Ice Age ended. The Han Dynasty and the Tang Dynasty were warm periods when the annual average temperature was about 2℃ higher than that of modern times. The research results have been widely used in climatology and historical geography. But in recent years, due to the discovery of new materials and the improvement of research methods, many scholars have supplemented Zhu Kezhen's work.

Zhu and others believe that since 2000-3000, climate change in China has gone through the following stages:

The cold and dry climate in the Western Zhou Dynasty (1 1 century to the middle of the 8th century BC);

From the Spring and Autumn Period to the early Western Han Dynasty (from the middle of the 8th century BC to BC 1 century BC), the climate was warm and humid.

The cold and dry climate from the late Western Han Dynasty to the Northern Dynasty (65438 BC+the middle of the 0 th century to the 6 th century);

During the Sui and Tang Dynasties (7th-8th century), the climate was warm and humid.

The cool and dry climate from the late Tang Dynasty to the Northern Song Dynasty (9- 1 1 century);

The dry and wet climate in the early Jin Dynasty (12nd century)

The cool and dry climate in the late Jin Dynasty and Yuan Dynasty (A.D. 13 and A.D. 65438+the first half of the 4th century)

During the Ming and Qing Dynasties (/kloc-the second half of the 4th century to the beginning of the 20th century), the climate was cold and dry. Later, many geographers made further modifications to the climate change in China, but the general trend is this.

In the historical period, the climate not only fluctuates periodically in temperature, causing temperature changes, but also changes in humidity. Generally speaking, warm period and wet period, cold period and dry period are corresponding, but each cold and warm period has wet and dry fluctuations, which cannot be generalized. Zhu and others believe that the change of temperature is faster than that of precipitation, and the change of precipitation is greater than that of temperature. In the historical period, there is obvious correlation between climate fluctuation and dry and wet fluctuation, but they are not completely synchronized.

Temperature and temperature zone 1. Temperature distribution in winter (1).

It can be seen from the isotherm map of 5438+ 10 in June that the 0℃ isotherm roughly passes through the southeast edge of Huaihe-Qinling-Qinghai-Tibet Plateau, and the temperature in the north of this line (including the northern region, the northwest inland and the inland of Qinghai-Tibet Plateau) is below 0℃, and the lowest temperature in Mohe, Heilongjiang Province is below -30℃. The temperature south of this line is above 0℃, and the lowest temperature in Sanya, Hainan is above 20℃. Therefore, it is warm in the south and cold in the north, and the temperature difference between the north and the south is large, which is the distribution characteristics of winter temperature in China. The main reasons for this feature are: the influence of latitude position, direct sunlight in the southern hemisphere in winter, and most parts of China are in the northern temperate zone, so solar radiation gets less heat. At the same time, the latitude difference between north and south is 50℃, and the height difference between north and south is significant, which leads to the low temperature in most parts of the north and the large temperature difference between north and south. The influence of winter winds In winter, cold and dry winter winds often blow from Mongolia and Siberia, and the northern region bears the brunt, thus aggravating the cold in the north and increasing the temperature difference between the north and the south. 2. Temperature distribution in summer (July)

It can be seen from the China summer isotherm map in July that the average temperature is above 20℃ in most areas except the Qinghai-Tibet Plateau and Tianshan Mountain, and above 28℃ in many places in the south. The Turpan Basin in Xinjiang has an average temperature of 32℃ in July, which is the hottest center in China in summer. Therefore, except the Qinghai-Tibet Plateau and other high-lying areas, the temperature is generally high in the whole country, and there is little difference between the north and the south, which is the characteristic of summer temperature distribution in China. The reasons are as follows: In summer, the direct sunlight point is in the northern hemisphere, and the sunlight and heat obtained in all parts of China generally increase. In addition, due to the high latitude and long days in the north, the light and heat gained are relatively increased, which shortens the temperature difference with the south, so the temperature in the whole country is generally high.

Division and cultivation of temperature zone

temperature band

Accumulated temperature ≥ 10℃

Growth period (days)

distribution range

Farming system

Main crops

tropical zone

& gt8000℃

365

Hainan and southern Yunnan, Guangdong and Taiwan Province provinces.

Rice is cooked three times a year.

Rice, sugarcane, natural rubber, etc.

Subtropical region

4500℃—8000℃

2 18—365

South of Qinhuai River, east of Qinghai-Tibet Plateau (that is, most parts of the south)

Two or three seasons a year.

Rice, winter wheat, cotton, rape, etc.

warm temperate zone

3400 —4500℃

17 1—2 18

Most of the middle and lower reaches of the Yellow River and southern Xinjiang (Tarim Basin)

One crop a year to three crops every two years.

Winter wheat, corn, cotton, peanuts, etc.

Middle temperate zone

1600 —3400℃

100— 17 1

Three northeastern provinces, most of Inner Mongolia, and northern Xinjiang

Once a year.

Spring wheat, corn, flax, soybean, beet, etc.

Low temperature zone

& lt 1600℃

& lt 100

A small part of northern Heilongjiang Province and a small part of northeastern Inner Mongolia.

Once a year.

Spring wheat, potatoes, etc.

Qinghai-Tibet Plateau

& lt2000℃ (in most areas)

0— 100

Qinghai-Tibet Plateau

In some areas, it is harvested once a year.

Highland barley, etc

3. China's temperature zone China uses accumulated temperature to divide the temperature zone. Most crops can only grow actively when the daily average temperature rises above 10℃, so the days when the daily average temperature is continuously ≥ 10℃ are usually called the growth period. The total temperature accumulated by the daily average temperature during the growth period is called accumulated temperature. The accumulated temperature of an area reflects the heat status of the area. According to the distribution of accumulated temperature, China has divided five temperature zones and a special Qinghai-Tibet Plateau. The heat in different temperature zones is different, the growth period is different, and the farming system and crop species are obviously different. Spatial distribution of precipitation and 1. The annual precipitation in dry and wet areas can be seen from the annual precipitation distribution map of China: the 800 mm isoprecipitation line is roughly on the southeast edge of Huaihe-Qinling-Qinghai-Tibet Plateau; The 400 mm isoprecipitation line is roughly at the southern end of Daxinganling-Zhangjiakou-Lanzhou-Lhasa-Himalayan Shandong. The annual precipitation in Tarim basin is less than 50 mm, and the precipitation in some areas of its southern margin is less than 20 mm; The average annual precipitation in Tuokexun, Turpan Basin is only 5.9mm, which is the "drought pole" of China. The precipitation in the southeast and south of China exceeds1.600mm, the eastern mountainous area of Taiwan Province Province exceeds 3000mm, and the annual average precipitation in Huoshaoliao in the northeast exceeds 6000mm, with a maximum of 8408mm, which is the "rain pole" of China. The spatial distribution of annual precipitation in China is decreasing from the southeast coast to the northwest inland. There are great differences among regions, generally, there are more coastal areas than inland areas, more southern areas than northern areas (except Qinghai-Tibet Plateau), more mountainous areas than plains, and more warm and humid air on windward slopes than leeward slopes in mountainous areas. 2. Time variation of precipitation The time variation of precipitation in China is manifested in two aspects, namely seasonal variation and interannual variation. Seasonal variation is the distribution of precipitation in a year. The seasonal distribution characteristics of precipitation in China are as follows: the annual rainy season starts from April to May and ends in about 10, lasting about 6-7 months, and the rainfall is concentrated in May 5- 10/0; The annual rainy season in the north (north) of Qinling-Huaihe River starts from July to August and ends in September. The rainy season lasts about 2-3 months, and the rain is concentrated in July and August. Most parts of this country are rainy in summer and autumn, but it seldom rains in winter and spring. Interannual variation is the distribution of precipitation between years. The interannual variation of precipitation in most parts of China is large, the interannual variation in rainy areas is less than the average temperature, and the interannual variation in less rainy areas is large. There is little interannual change in coastal areas and great interannual change in inland areas. The interannual variation of inland basins is the largest. 3. Monsoon activity and the spatial distribution and temporal variation of precipitation in China monsoon region are mainly caused by the influence of monsoon activity. The southeast monsoon originating from the tropical sea surface of the western Pacific Ocean and the southwest monsoon of the Indian Ocean near the equator blow warm and humid air to Chinese mainland, which becomes the main source of water vapor for summer precipitation in China. In the year when the summer monsoon is normally active, the warm and humid summer winds push to Nanling and its south in April and May every year. Guangdong, Guangxi, Hainan and other provinces have entered the rainy season, and the precipitation has increased. In June, the wind blows to the middle and lower reaches of the Yangtze River in summer, and the vast area south of Qinling-Huaihe River enters the rainy season (except some areas). At this time, it is raining continuously in the Jianghuai area. Because it is the season when plums are yellow and ripe, it is called rainy weather. In July and August, the summer wind blows to the area north of Qinling-Huaihe River, and East China and Northeast China enter the rainy season, and the precipitation is significantly higher than that before July and August. In September, the influence of cold air in the north was enhanced, and the warm and humid summer monsoon was pushed south, and the rainy season in the north ended. In June+10, 5438, the summer monsoon withdrew from Chinese mainland, and the rainy season in the south also ended.

Division of dry and wet areas

Annual precipitation (mm)

Dry and humid conditions

Distribution area

plant

Land use

Moist zone

& gt 800

Precipitation > evaporation

South of Huaihe River in Qinling Mountains, southernmost part of Qinghai-Tibet Plateau (south of southern Tibet Valley), northeastern Inner Mongolia and eastern part of three northeastern provinces.

forest

Agriculture dominated by paddy fields

Semi-humid area

& gt celebrities

Precipitation > evaporation

Northeast Plain, North China Plain, Most of Loess Plateau, Southeast of Qinghai-Tibet Plateau (North of Southern Tibet Valley)

forest steppe

Dryland agriculture

Semi-arid area

& lt Celebrity

precipitation