Geographical characteristics of Yunnan

Yunnan, called Dian for short, is located in the southwest border of China, with 2 1 8' 32-29 15' 8 north latitude and 97 31'39-1061'47 east longitude. The maximum horizontal distance from east to west is 864.9 kilometers, and the maximum vertical distance from north to south is 990 kilometers, with a total area of 394,000 square kilometers, accounting for 4. 1% of the national total area, ranking eighth in the country. Yunnan Province borders Myanmar in the west and southwest, Vietnam and Laos in the south, Guangxi Zhuang Autonomous Region and Guizhou Province in the east, Sichuan Province in the north and Xizang Autonomous Region in the northwest. The border line is 406 1 km, which is one of the provinces with the largest number of neighboring countries and the longest border line in China. There are 8 border prefectures and 26 border counties in Yunnan, and 1 1 national ports, 9 provincial ports and nearly 100 border ports have been opened. It is convenient to communicate with neighboring countries and even other countries and regions in Southeast Asia and South Asia. It is the main land route for China to communicate with Southeast Asia and South Asia, and the opening conditions along the border are extremely favorable. Two. Population, Ethnic Groups and Administrative Divisions 200 1 At the end of the year, the total population of Yunnan Province was 42.874 million. Except the Han nationality, there are 25 ethnic minorities with a population of over 50 million, of which 15 is unique to Yunnan, and the population of ethnic minorities accounts for13 of the total population of the province. Yunnan is not only a province with a large population of ethnic minorities, but also a province with the largest number of ethnic minorities in China. In addition, Yunnan is also the province with the largest number of cross-border ethnic groups in China. Of the 25 ethnic minorities, 13 have crossed the borders of China, Vietnam, Laos and Myanmar respectively, distributed in vast areas in northern Vietnam, Laos and Myanmar, and some ethnic groups have also extended to Thailand, Cambodia and India. There are many cross-border nationalities, which increases a blood relationship with the people of neighboring countries and is very beneficial to Yunnan's opening up. Yunnan province governs 16 cities, including 8 ethnic autonomous prefectures, 5 provincial cities and 3 regions. * * County-level administrative units 128, including 29 ethnic autonomous counties. Kunming, the provincial capital, and other major cities are Yuxi, Qujing, Gejiu, Dali, Chuxiong, Baoshan, Lijiang, Simao, Jinghong and Ruili. 3. Topography Yunnan is high in the northwest and low in the southeast, with great differences in altitude. The highest point is the Kage peak, which is the main peak of Meili Snow Mountain in Deqin County at the junction of Yunnan and Tibet, with an altitude of 6740 meters. The lowest point is at the intersection of nanxi river and Yuanjiang in Hekou County bordering Vietnam, with an altitude of only 76.4 meters. The linear distance between the two places is 900 kilometers, and the height difference is more than 6000 meters. Yunnan is a part of the southern extension of the Qinghai-Tibet Plateau. The terrain is divided into two parts with Yuanjiang Valley and the wide valley in the southern section of Yunling Mountain as the boundary. East Yunnan is the eastern part of the central Yunnan Plateau, with little topographic relief, with an average elevation of about 2000 meters. Characterized by gently undulating low mountains and round hills, various types of karst landforms are developed. The west is the longitudinal valley area of Hengduan Mountains, with mountains and deep valleys alternating. The relative height difference is large and the terrain is steep. The elevation in the southwest is generally 1500-2200m, and the elevation in the northwest is generally 3000-4000m. Only in the southwest border area did the terrain gradually flatten. The valley here is wide, with an altitude of 800- 1000 meters, and the drop in some areas is below 500 meters, forming the main tropical and subtropical areas in Yunnan. Yunnan landform has five characteristics:

First, the plateau fluctuates. Relatively gentle mountainous areas only account for 10% of the total area, and a large area of land has different heights, ups and downs, and a certain range is a gentle plateau.

Second, mountains and valleys alternate with each other. There is a famous longitudinal valley area in western Yunnan in northwest Yunnan. Gaoligong Mountain is the watershed of Irrawaddy River and Nujiang River, Nushan Mountain is the watershed of Nujiang River and Lancang River, and Yunling Mountain is the watershed of Lancang River and Jinsha River. The river was strongly cut, forming an extremely magnificent landform. Nujiang Gorge, Lancang Gorge and Jinshajiang Gorge are magnificent. The relative height difference of alpine valleys exceeds 1000m, of which Nujiang Canyon is more than 300 km long from north to south, so it is called "Oriental Grand Canyon". The top of the mountain above 5000 meters is covered with snow all year round, forming a strange and magnificent alpine glacier landform. Tiger Leaping Gorge in Jinsha River is one of the world-famous canyons, with a relative height difference of more than 3,000 meters from the mountains on both sides. The straight-line distance from the west swinging iron cable of Lancang River to the top of Kage peak of Meili Snow Mountain is about 12km, and the height difference actually reaches 4,760m m. In the narrow range of 10km, it presents a peculiar landscape of subtropical dry-hot valley and alpine ice and snow world, and the natural scenery is equivalent to the latitude from Guangdong to Heilongjiang, which is rare in China. The third is the gradual decline of the terrain. The whole province is divided into three steps, the first step is in Deqin and Shangri-La counties in northwest Yunnan, the second step is in the central Yunnan Plateau, and the third step is in the south, southeast and southwest, with an average drop of 6 meters per kilometer. Fourth, the fault basins are scattered. Basins and plateaus, commonly known as "bazi" in the southwest, can be seen everywhere in Yunnan. Yunnan has 1442 dams with an area of 1 km2, and 49 dams with an area of100km2. The largest dam is Lvliang Dam, followed by Kunming Dam. Fifth, rivers crisscross and lakes are dotted. There are not only many mountains, but also many rivers and lakes in Yunnan, which constitute the characteristics of vertical and horizontal mountains, intertwined water systems and scattered lakes. Mountain systems mainly include Wumeng Mountain, Hengduan Mountain, Ailao Mountain and Wuliang Mountain. There are more than 600 rivers in Yunnan, belonging to Irrawaddy River, Nujiang River, Lancang River, Jinsha River (Yangtze River), Yuanjiang River (Red River) and Nanpanjiang River (Pearl River). These rivers flow into the South China Sea and the Indian Ocean respectively, and most of them have the characteristics of large drop and rapid flow, and are extremely rich in hydropower resources. Among them, Irrawaddy River, Nujiang River, Lancang River and Yuanjiang River are international rivers. There are more than 40 plateau lakes in Yunnan. The famous lakes are Dianchi Lake, Erhai Lake, Fuxian Lake, Xingyun Lake, Yangzonghai Lake, Chenghai Lake and Lugu Lake. Natural lakes are like pearls, dotted among mountains, which are particularly magnificent and crystal clear. Four. Climate types and characteristics Yunnan is located in the low latitude plateau, which is controlled by dry continental monsoon in winter and humid maritime monsoon in summer. The climate mainly belongs to low latitude mountain monsoon climate. The climate types in the province are rich and diverse, including seven climate types: north tropical, south subtropical, middle subtropical, north subtropical, south temperate, middle temperate and plateau climate zone. Due to the complex terrain, large vertical height difference and obvious three-dimensional climate characteristics. The most prominent features are small annual temperature difference and large daily temperature difference; Sufficient precipitation, clear dry and wet, uneven distribution; There are obvious differences in vertical climate change. There are many rainy days in summer, the sun is covered by clouds, and the temperature is not high enough. The hottest days are generally between 19-22 degrees Celsius. Winter is controlled by dry warm current, with sunny days, abundant sunshine and high temperature. The average temperature in Leng Yue is above 6-8 degrees Celsius, and the annual temperature difference is generally only 10- 12 degrees Celsius, and the temperature is even lower in rainy days. Judging from the daily temperature change, it is cooler in the morning and evening and hotter at noon, especially in winter and spring, and the daily temperature difference can reach 12-20 degrees Celsius. The amount of water in most parts of the province is above 1000mm, but the distribution of precipitation is extremely uneven in seasons and regions. 85% of the rainfall is concentrated in the rainy season from May to 65438+1October, especially in June, July and August. The dry season is 1 1 to April of the following year, and the precipitation only accounts for 15% of the whole year. The regional distribution of precipitation is very uneven. The annual precipitation in the most places can reach 2200-2700 mm, and the annual precipitation in the least places is only 580 mm. Because the increase of latitude in the horizontal direction coincides with the increase of altitude, the climate in the eight latitudes of the province presents three zones of cold, warm and hot. Generally speaking, the temperature drops by about 0. Every time the height rises 100 m, it drops by 6℃. Therefore, "one mountain is divided into four seasons, and ten miles is different from the sky" has become a vivid portrayal of Yunnan's climate diversity. Yunnan has a long frost-free period. The southern border is frost-free all year round. The frost-free period is 300-330 days in Wenshan, Mengzi, Simao, Lincang and Dehong in the south, 250 days in Kunming, Yuxi and Chuxiong in the middle, and 2 10-220 days in Zhaotong and Lijiang, which are colder. In addition, Yunnan has good lighting conditions, with 90- 150 kcal per square centimeter per year, second only to Tibet, Qinghai, Inner Mongolia and other provinces. The above climatic characteristics of Yunnan are suitable for the growth of many kinds of organisms, which has laid a good foundation for the province to innovate agriculture, develop biological resources and produce characteristic products.