Tibet has a vast territory, spectacular landforms and rich resources, so I believe that many people have a Tibetan dream. Tibet, with an average altitude of more than 4000 kilometers, is known as the "roof of the world". Tibet is famous for its magnificent and magical natural scenery. So, what climate does Tibet belong to? What clothes are suitable for a trip to Tibet?
Due to the unique topography, high altitude air environment and weather system, Tibet Plateau has formed a complex and diverse unique climate. In addition to the cold and dry northwest and warm and humid southeast, there are also a variety of regional climate and obvious vertical climate zone.
The air is thin, the air pressure is low, and the oxygen is low. At sea level, the air density is 1292 grams per cubic meter and the standard air pressure is 1013.2 milligrams at zero centigrade. The air density and air pressure in plain area are similar to sea level. In Lhasa City (3658 meters above sea level), located in the Tibetan Plateau, the air density is 810 grams per cubic meter, and the annual average pressure is 652 milligrams, 62.64% and 64.35% of that in the plain area, respectively, which is less or one third lower than that in the plain area. There is enough oxygen in the plain area, 250-260 grams of oxygen per cubic meter of air, and only 150-170 grams of oxygen per cubic meter of air in the Tibet Plateau, the place with the lowest temperature in summer. Especially in northern Tibet, the temperature in July is lower than 8 ℃.
From the point of view of temperature difference, Tibet has the characteristics of small annual and large daily temperature range. The annual range of Lhasa, Changdu and Shigatse is 18-20 ℃, while that of Wuhan and Nanjing with similar latitude is 26 ℃. The annual average daily range is 14-16 ℃ in Lhasa, Changdu and Shigatse, while only 7 ℃ in Chengdu, Changsha and Nanchang. The daily range of setting day is 18.2 degrees Celsius, about 2.5 times of Nanchang, which has similar latitude. At an altitude of more than 5000 meters in Ali area, the temperature of white weather in August in summer can reach more than 10 degrees Celsius, and the temperature at night can drop below zero degrees Celsius. Lhasa and Shigatse, which are located in the Yarlung Zangbo River Valley, have a maximum temperature of 27-29 degrees Celsius at noon in June, which gives people a feeling of summer; when the temperature drops in the evening, people feel cool in autumn; when the temperature drops to 5 degrees Celsius at midnight, they need to cover the quilt all night; after sunrise in the next morning, the temperature rises again, which gives people a sense of spring. It's true that 'although there are four seasons in a year, cold clothes are prepared all year round'.
Tibet's annual temperature range is small and daily temperature range is large, which is a favorable climate condition. The annual range is small, and the winter temperature is not too low. The winter crops can survive smoothly under a certain height, and can plant large areas of winter wheat, highland barley and other crops. The daily range is large and the temperature in white weather is high, which is conducive to photosynthesis of plants; the temperature at night is low, which can reduce the respiratory loss of plants, and is conducive to the accumulation of plant nutrients.
The dry season and rainy season are distinct, and there is more rain at night. Due to the different origin, nature and control time of the winter westerly and summer southwest monsoon, the seasonal distribution of precipitation in Tibet is very uneven, and the distinction between the dry season and the rainy season is very obvious.
From October to April of the next year, there is a westerly jet over the Tibet Plateau. The ground is controlled by cold and high pressure. It is dry and windy, with low temperature and little rain and snow. The precipitation only accounts for 10-20% of the annual precipitation. For example, the precipitation in Lhasa from October to April of the next year 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 is controlled by thermal depression, and the southwest monsoon ascends the plateau. Under its control, the rainfall in Tibet is very concentrated, generally accounting for about 90% of the annual rainfall. For example, the precipitation from May to September in Lhasa accounts for 97% of the total annual precipitation, so it is called rainy season or wet season. In the rainy season, there is more night rain, thunderstorm and hail. Southern Tibet is dominated by night rain, which can account for more than 80% of the precipitation in rainy season. Thunderstorms and hailstorms are frequent in the rainy season in the northern Tibetan Plateau, such as Naqu, soxian and other places, which have more than 85 thunderstorm days in a year, making them the most thunderstorm days in the same latitude in the northern hemisphere. The number of hail days in Tibet Plateau ranks first in China. The average hail day in Naqu was 35 days, and 64 days in 1954, which was rare in the world.
The climate type is complex and the vertical variation is large. The terrain of Tibet is high in the northwest and low in the southeast. The altitude of the plateau in the north of Tibet is 4500-5000 meters, and the altitude of the valley in the southeast of Tibet is less than 1000 meters. From southeast to northwest, its climate features are divided into tropical mountain monsoon humid climate subtropical mountain monsoon humid climate plateau temperate monsoon semi humid, semi-arid climate plateau sub cold monsoon semi humid, semi-arid and arid climate plateau cold monsoon arid climate.
In the Southeast Tibet and the South Himalayan mountain canyon area, from the bottom to the top, the climate changes vertically from tropical or subtropical climate to temperate, cold temperate and cold zone climate because of the increasing terrain and the decreasing temperature. The plain area is thousands of kilometers away from the south to the north to present the natural scene of the three zones of heat, temperature and cold. Here, from the low to the high, it appears within the horizontal distance of only tens of kilometers. It's true that "one mountain has four seasons and ten li has different days".