Why is the altitude of 5000 meters a forbidden area for skydiving?

There are two main reasons for the no-jump zone above 5000 meters, namely, low temperature and unstable atmosphere (such as excessive wind speed). The following is an explanation.

The troposphere is located at the bottom of the atmosphere, which concentrates about 75% of the atmospheric mass and more than 90% of the water vapor mass. The average altitude is 17 ~ 18km in low latitudes, 10 ~ 12km in mid latitudes and 8 ~ 9km in polar regions.

In the troposphere, the temperature decreases with the elevation, with an average increase of 100 m, and the temperature decreases by about 0.65℃.

In the troposphere, according to the distribution characteristics of airflow and weather phenomena, it can be divided into low layer, middle layer and high layer. ?

(1) Lower layer: The lower layer is also called disturbance layer or friction layer. It generally ranges from the ground to a height of 2 kilometers. With the difference of seasons and days and nights, there are some changes in the scope of the lower layer, which is generally higher in summer than in winter and higher in day than at night. In this layer, the airflow is greatly influenced by ground friction, and the turbulent exchange is particularly strong. Usually with the increase of height, the wind speed increases and the wind direction deflects. This layer is affected by the ground thermal effect, and the temperature also has obvious diurnal variation. Because of the high content of water vapor and dust particles in this layer, low clouds, fog and floating dust often appear. ?

(2) Intermediate layer: The bottom boundary of the intermediate layer is at the top of the friction layer, and the height of the upper layer is about 6 kilometers. The influence of the ground is much less than that of the friction layer, and the airflow can basically represent the air movement trend of the whole troposphere. Most of the clouds and precipitation in the atmosphere are generated in this layer. ?

(3) Upper layer: The upper layer extends from a height of 6 kilometers to the tropopause. This layer is less affected by the ground, the temperature is below 0℃ all the year round, the water vapor content is less, and all kinds of clouds are composed of ice crystals and supercooled water droplets. In mid-latitude and tropical areas, strong wind belts with wind speed equal to or greater than 30m/s often appear in this layer, which is called jet stream.

Jumping 5000 meters is of course too high.