What is the climate like in Tibet?

Due to the peculiar and diverse topography, high-altitude air environment and weather system in Tibet Plateau, a complex and unique climate has been formed. In addition to the general trend of cold and dry northwest and warm and humid southeast, there are various regional climates and obvious vertical climatic zones.

(1) The air is thin, the air pressure is low, and there is little oxygen. At sea level, the air density is 1.292g per cubic meter, and the standard air pressure is1.013.2mg. The air density and air pressure in plain areas are almost the same as those at sea level. In Lhasa (3,658 meters above sea level), the air density is 865,438 per cubic meter. The rates in plain areas are 62.64% and 64.35% respectively, which are less than one third or more than one third lower than those in plain areas. The air in the plain is relatively rich, with 250-260 grams of oxygen per cubic meter, while the air in the Qinghai-Tibet Plateau only contains 150- 170 grams of oxygen per cubic meter, with the lowest temperature in summer, especially in northern Tibet, where the temperature is below 8 degrees Celsius in summer and July.

Judging from the temperature difference, the annual temperature difference is small, and the daily temperature difference in Tibet is particularly obvious. The annual temperature difference between Lhasa, Qamdo and Shigatse is 18-20 degrees Celsius, while Wuhan and Nanjing with similar latitudes are 26 degrees Celsius. The annual average daily range of Lhasa, Qamdo and Shigatse is 14- 16 degrees Celsius. Chengdu, Changsha and Nanchang are only 7 degrees Celsius. The daily range is 18.2 degrees Celsius, which is about 2.5 times that of Nanchang at the same latitude. At an altitude of more than 5,000 meters in Ali, the daytime temperature can reach 10 degrees Celsius in summer and August, and the nighttime temperature drops below zero degrees Celsius. In Lhasa and Shigatse, in the Yarlung Zangbo River basin, the highest temperature can reach 27-29 at noon in June. When the temperature drops at night, people will feel cool in autumn. At midnight, the temperature drops to 5 degrees Celsius, and the quilt should be covered all night; After sunrise in Rosty Yi, the temperature rises, giving people a feeling of spring.

Tibet's small annual temperature difference and large daily temperature difference are favorable climatic conditions. The annual range is small, and the temperature will not be too low in winter. At a certain height, overwintering crops can overwinter smoothly, and crops such as winter wheat and highland barley can be planted in a large area. Large diurnal range and high daytime temperature are beneficial to plant photosynthesis. Low temperature at night can reduce the respiratory loss of plants and is beneficial to the accumulation of plant nutrients.

(4) The dry season and rainy season are distinct, and it rains many nights. Due to the different sources, properties and control time of the west wind in winter and the southwest monsoon in summer, the seasonal distribution of precipitation in Tibet is very uneven, and the distinction between dry season and rainy season is very obvious.

Every year 10 to April, the ground in westerly jet over the Qinghai-Tibet Plateau is controlled by cold and high pressure. It is dry and windy, with low temperature and little rain and snow. Precipitation only accounts for 10-20% of the annual precipitation. For example, the precipitation in Lhasa/KLOC from October to April only accounts for 3% of the annual precipitation, so it is called dry (dry) season or windy season.

From May to September, the surface layer of the plateau was controlled by low temperature, and the southwest monsoon landed on the plateau. Under its control, rainfall in all parts of Tibet is very concentrated, generally accounting for about 90% of the annual precipitation. For example, the precipitation in Lhasa from May to September accounts for 97% of the total precipitation in the whole year, so it is called rainy season or wet season. In the rainy season, there are many nights of rain, thunderstorms and hail. The southern part of Tibet is dominated by night rain, which can account for 80% of the rainy season precipitation. For example, Naqu and Suoxian have more than 85 thunderstorm days a year, which is the region with the most thunderstorm days at the same latitude in the northern hemisphere. The number of hail days in Tibet Plateau ranks first in China. The average number of hail days in Naqu is as high as 35 days, and it rained for 64 days in 1954, which is rare in the world.

(5) The climate type is complex and the vertical variation is great. Tibet is high in the northwest and low in the southeast. The plateau in northern Tibet is 4500-5000m above sea level, and the valley in southeastern Tibet is below1000m above sea level. Its climatic characteristics are divided from southeast to northwest: tropical mountain monsoon humid climate-subtropical mountain monsoon humid climate-semi-humid and semi-arid climate of plateau temperate monsoon-semi-humid, semi-arid and arid climate of plateau sub-cold monsoon.

In the alpine valleys of southeast Tibet and the southern slopes of Himalayas, from bottom to top, due to the rising terrain, the temperature gradually drops, and the climate changes vertically from tropical or subtropical climate to temperate climate, cold temperate climate and cold zone climate. The natural scenes of heat, temperature and cold can only be presented in the plain area with thousands of kilometers apart from south to north, but here it only appears within a horizontal distance of tens of kilometers from low to high. It's really "four seasons in one mountain, ten miles in different days"

According to the distribution of climate types, the areas below 1 100 meters above sea level in southeastern Tibet and the southern slope of Himalayas belong to tropical mountain monsoon humid climate. The average temperature in the warmest month here is above 22 degrees Celsius, and the average temperature in Leng Yue is below 13 degrees Celsius, which is higher than that in eastern China at the same latitude. The annual precipitation is 2,500 mm, reaching 4,495 mm in some places, which is the region with the most rainfall in Tibet. It is also one of the rainy areas in China. Here, the trees are lush, the seasons are evergreen, all kinds of tropical plants grow luxuriantly, vines are entangled, and the wild banana, wild lemon forest and bamboo forest all over the mountains constitute a beautiful tropical scenery. Tropical cash crops can be planted here and harvested three times a year.

These areas are located at an altitude of 1 100-2500m, and belong to subtropical monsoon humid climate. The average temperature in the warmest month is 18-22 degrees Celsius, and the annual precipitation is about 1000 mm. It is warm all year round, with abundant rainfall, subtropical evergreen broad-leaved trees grow and crops are harvested twice a year.

The Yarlung Zangbo River basin, north of Himalayas, south of Gangdise Mountain and Nyainqentanglha Mountain, is 500-4200m above sea level, and belongs to the semi-humid and semi-arid climate of plateau temperate monsoon. The average temperature in the warmest month is 10- 18 degrees Celsius, and the annual precipitation is 400-800 mm. Cool crops such as wheat, highland barley and potato and temperate fruit trees can be planted, and crops can be harvested once a year.

The lake basin area in the south of northern Tibet Plateau, north of Gangdise Mountain and Nyainqentanglha Mountain, is 4200-4700 meters above sea level, and belongs to the monsoon semi-arid and arid climate in the plateau sub-cold zone. The average temperature in the warmest month is 6- 10 degrees Celsius, and the annual precipitation is100-300mm. It is a prairie in Tibet, with animal husbandry as the main industry.

The plateau in northern Tibet is 4700-5500 meters above sea level, which belongs to the monsoon dry climate in the cold region of the plateau. The average temperature in the warmest month is below 6 degrees Celsius, and the annual precipitation is100-150 mm. It is a vast natural pasture. The area above 5500 meters is covered with snow all year round, which is a crystal clear and jade-like world of ice and snow.