The climate, topography and influences of the Qinghai Tibet region

The climate is dominated by alpine plateaus. Due to its height, the air on the Tibetan Plateau is relatively dry and thin, with relatively strong solar radiation and relatively low temperatures. Due to the complexity and variability of its topography, the climate itself on the Tibetan Plateau varies greatly from region to region.

In general, there is less rainfall on the plateau.

The Tibetan Plateau itself is also an important factor influencing the Earth's climate. Paleontology and geology have shown that the uplift of the Tibetan Plateau has brought about dramatic changes in the global climate. As a tall wind screen, it effectively blocks the cold air of the northern continent from entering South Asia.

At the same time, the Himalayas block the northward flow of warm and humid air from the south, which is an important factor in the rainy season in South Asia.

The influence of the topography of the Qinghai-Tibet region on the climate can be divided into two aspects:

1. Dynamic effect: forced branch of the westerly wind belt: clockwise circulation on the north side, dry and cold climate; The south side has a counterclockwise circulation, and the climate is warm and humid. For example, Lanzhou is dry and cold, and the Sichuan Basin is warm and humid.

The southwesterly airflow on the south side of the plateau transports water vapor from the Bay of Bengal to the Yangtze River Basin, which has an important impact on the precipitation in eastern China.

2. Thermodynamics: In winter, the plateau is the cold source, the air pressure field is cold and high-pressure, and the climate is dry and cold. Summer is a source of heat, low pressure prevails, air rises, and cloudy and rainy weather. This effect is consistent with the monsoon climate caused by the distribution of sea and land, and has a strong promoting effect on the monsoon climate in Southeast Asia.

In addition, the strong Qinghai-Tibet high at the tropopause formed by thermal action in summer is an important atmospheric system that affects the weather and climate of the Northern Hemisphere in summer.

Due to the uplift of the Qinghai-Tibet Plateau, the East Asian monsoon circulation in China is stronger, the winter and summer monsoon changes more obviously, the continental climate characteristics are more prominent, and the winter monsoon affects longer and more extensively.

The uplift of the Qinghai-Tibet Plateau has formed a relatively independent climatic unit in the eastern part of China, which makes the difference in the thermal properties of land and sea in China extremely obvious. Due to the high terrain, in summer, the atmosphere over the Qinghai-Tibet Plateau heats up quickly, the airflow rises, and the air pressure decreases, which accelerates the formation of onshore low pressure, so that the summer monsoon blowing from the ocean to the land strengthens and even affects the eastern and southern parts of the Qinghai-Tibet Plateau. In winter, the atmosphere over the Qinghai-Tibet Plateau cools down rapidly and the air flow sinks, which increases the force of high pressure over the land and promotes the air flow to blow from the land to the sea.

In winter, because it is difficult for air from higher latitudes to cross the Tibetan Plateau, the areas south of the Tibetan Plateau are less affected by the winter monsoon, and the temperature drops less. In summer, because the southwest monsoon from the Indian Ocean rarely crosses the Qinghai-Tibet Plateau into the northwest of China, the climate in Gansu and Xinjiang will be arid.

The Qinghai-Tibet Plateau blocks the low-level westerly airflow in China, dividing it into two branches, the south and the north (the branch point is at 60°E), and the northern branch airflow flows to the Pacific Ocean through Northwest, North, Northeast and East China. The southern branch airflow turned into a southwesterly airstream with high temperature and humidity after flowing over the southern side of the Tibetan Plateau, affecting Sichuan, Guizhou, Yunnan, South China and the middle and lower reaches of the Yangtze River in China, and the two airstreams finally converged near 110°E in the eastern part of the Tibetan Plateau.

The average height of the Qinghai-Tibet Plateau is more than 4,000 meters, the area is very large, and the characteristics of the plateau climate are more prominent. The main characteristics of the Qinghai-Tibet Plateau climate are:

1. Due to the small thickness of the atmosphere on the Qinghai-Tibet Plateau and the low content of water vapor, the radiation intensity is large, and the ultraviolet radiation intensity increases more;

2. The diurnal variation of temperature on the Qinghai-Tibet Listool Plateau is significant, and the diurnal variation of temperature is about 1 to 2 times higher than that in eastern China, and the temperature is relatively low.

3. The edge of the oceanic airflow on the Qinghai-Tibet Plateau is a rainy belt, while the edge of the oceanic airflow facing from it has less rainfall. For example, the average annual precipitation in the southern foothills of the Qinghai-Tibet Plateau is 11,429 mm, while the hinterland, western and northern parts of the Qinghai-Tibet Plateau receive less than 100 mm of precipitation.

4. Due to the high Qinghai-Tibet level.