1, low atmospheric pressure, low oxygen partial pressure The atmospheric pressure at sea level is 101.3kPa (760mmHg), called an atmospheric pressure. The oxygen concentration in the atmosphere (volume percentage) does not change with the increase in altitude, and is constant at 20.95%. The partial pressure of oxygen = atmospheric pressure × oxygen concentration, thus the partial pressure of oxygen at sea level is 21.2kPa (159mmHg). The higher the altitude, the lower the atmospheric pressure, the lower the partial pressure of oxygen. As the altitude increases, the boiling point of water also decreases. Generally speaking, for every 100 meters of elevation, the atmospheric pressure decreases by about 0.7kPa (5mmHg) and the boiling point of water decreases by about 0.33℃. 2.Long sunshine and strong radiation The plateau is high, sunrise is early, sunset is late, and sunshine time is long. The atmosphere on the plateau is thin, with little water vapor and impurity content, and the proportion of ultraviolet light in daylight is also large due to the high transmission rate of daylight radiation. In addition, the amount of more penetrating cosmic rays from outer space increases on the plateau. In the area of 4,000 meters above sea level, the UV intensity is 1.5 to 2.5 times higher than sea level. In the area of 3000 meters above sea level, the total annual amount of cosmic rays is about 3 times higher than the plain. 3.Cold, windy and dry Even in summer, the snow on the plateau above 5,000 meters above sea level does not melt all year round. In addition, the plateau has a typical continental climate, with high temperature at noon and low temperature in the morning and evening, and the temperature difference can be 15~30℃ in a day. In addition, the speed of airflow accelerates with the increase of altitude. Above 5,000 meters above sea level, the wind is blowing in the afternoon. Strong wind and lower atmospheric temperature, accelerate the role of evaporation of moisture on the surface of the body, thus further aggravating the degree of cold. The higher the altitude, the lower the temperature, the farther from the coastline, the less water vapor contained in the atmosphere, the drier the air. If the absolute content of water vapor in the atmosphere at sea level as 100%, the absolute content of water vapor at an altitude of 3000 meters is only 26%. 4.Dry and wet seasons are clearly distinguished The plateau has wet and warm precipitation weather due to the hot and low pressure in summer, and the cold and high pressure in winter forms dry and cold windy weather, and the unique plateau monsoon produces obvious changes of dry and wet seasons. The westerly wind belt controls the plateau area in the winter months for the dry season; the summer months are influenced by the humid southwest and southeast monsoons, and precipitation increases significantly. Thus, there is a clear alternation of wet and dry seasons. In addition, the precipitation on the Qinghai-Tibet Plateau is characterized by many thunderstorms, hailstorms and night rains.