Millions of years ago, the Qinghai-Tibet Plateau uplifted, which was a major crustal movement in the history of the earth and formed the landform of China. Overlooking the land of China from the air, the terrain is like a ladder, descending gradually from west to east. Influenced by the Indian plate and the Eurasian plate, the Qinghai-Tibet Plateau is rising continuously, with an average elevation of more than 4,000 meters. It is called "the roof of the world" and constitutes the first step of Chinese topography. Mount Everest, the main peak of the Himalayas on the plateau, is 8844.43 meters high, which is the highest peak in the world. The second level consists of Inner Mongolia Plateau, Loess Plateau, Yunnan-Guizhou Plateau, Tarim Basin, Junggar Basin and Sichuan Basin, with an average elevation of 1000-2000m. The eastern edge of the second step passes through Daxing 'anling, Taihang Mountain, Wushan Mountain and Xuefeng Mountain, and the third step reaches the Pacific coast eastward. The terrain of this step drops to 1000 meters below 500 meters. Northeast Plain, North China Plain and the middle and lower reaches of the Yangtze River are distributed from north to south, and the edge of the plain is inlaid with low mountains and hills. Further east is the shallow sea area of China continental shelf, which is the fourth level, water depth, temperature and temperature area.
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.