Basic knowledge of world geography

1. The temperature distribution in winter can be seen from the isotherm of 1: 0℃ passing through the southeastern edge of Huaihe-Qinling-Qinghai-Tibet Plateau. The temperature in the north of this line (including the north, northwest inland and Qinghai-Tibet Plateau) is below 0℃, and the temperature in Mohe, Heilongjiang is below -30℃. The temperature in the south of this line is above 0℃, and the 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 In winter, the sun shines directly in the southern hemisphere, 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, so the temperature in most parts of the north is low and the temperature difference between north and south is large.

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. From the isotherm map of China in July in summer, we can see the distribution of summer temperature: except the Qinghai-Tibet Plateau and Tianshan Mountain, most areas are above 20℃, and many places in the south are above 28℃; 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 Huaihe River in Qinling Mountains and east of Qinghai-Tibet Plateau

Two or three seasons a year.

Rice, winter wheat, cotton, rape, etc.

warm temperate zone

3400 —4500℃

17 1—2 18

The middle and lower reaches of the Yellow River and most parts of southern Xinjiang

One crop a year to three crops every two years.

Winter wheat, corn, cotton, peanuts, etc.

Middle temperate zone

1600 —3400℃

100— 17 1

Northeast China, most of Inner Mongolia, northern Xinjiang

Once a year.

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

Low temperature zone

& lt 1600℃

& lt 100

Northern Heilongjiang Province and Northeast Inner Mongolia

Once a year.

Spring wheat, potatoes, etc.

Qinghai-Tibet Plateau

& lt2000℃

(Most regions)

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.

Precipitation and dry and wet areas

1. The spatial distribution of annual precipitation can be seen from the annual precipitation distribution map of China: the 800 mm isoprecipitation line is on the southeast edge of Huaihe-Qinling-Qinghai-Tibet Plateau; The 400 mm isoprecipitation line is on the line from Daxinganling-Zhangjiakou-Lanzhou-Lhasa-the southern tip of 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 some parts of southeast China is above 1600 mm, in the eastern mountainous area of Taiwan Province Province it is above 3000 mm, and the average annual precipitation in Huoshaoliao in northeast China is above 6000 mm, and the most frequent one is 8408 mm, 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 between regions. Generally, there are more coastal areas than inland areas, more southern areas than northern areas, more mountainous areas than plains, and more windward slopes than leeward slopes of warm and humid air 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 rainy season in the south starts early and ends late, and the rainy season is long, concentrated in May-10; The rainy season in the north starts late and ends early, and the rainy season is short, 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 areas of China is large, but it is small in rainy areas and large in less rainy areas. 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 entered the rainy season, and precipitation increased.

In June, the summer wind blows to the middle and lower reaches of the Yangtze River, and the vast area south of Qinling-Huaihe River enters the rainy season. 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 north of Qinling-Huaihe River, and East China and Northeast China enter the rainy season, and the precipitation increases obviously. 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, south of Qinghai-Tibet Plateau, northeast of Inner Mongolia and east 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

forest steppe

Dryland agriculture

Semi-arid area

& lt Celebrity

precipitation