The influence of Qinghai-Tibet Plateau on monsoon climate, thank you.

From March to May every year, cold air comes from the north and warm and humid air flows from the south, and the two meet in the south of the Yangtze River basin to form precipitation. This is closely related to the Qinghai-Tibet Plateau.

About 240 million years ago, due to the crustal plate movement, the separated Indian plate moved northward and squeezed at a relatively fast speed, and strong folds, faults and uplifts appeared in the north. As the Indian plate continued to insert northward under the ancient oceanic crust, about 80 million years ago, parts of northern and southern Tibet broke away from the ocean and became land, eventually forming the Qinghai-Tibet Plateau, the "roof of the world" on the earth today.

The characteristics of the Qinghai-Tibet Plateau can be summarized as "five degrees", that is, scale, longitude, latitude, height and slope: it spans Eurasia, is located in the east of Eurasia, at the intersection of the east and west wind belts, and is located in the subtropical region of Eurasia, reaching the upper and middle troposphere, with steep terrain in the east and south. The Qinghai-Tibet Plateau accounts for 1/4 of China's land area, successfully separating the climate in the mid-latitude region from that in the tropical region. The Qinghai-Tibet Plateau is very high and has a wide range. The airflow in the westerly belt will fluctuate when it meets, just like the river meets the stone. Fluctuations will affect downstream areas as far as the American continent.

There is a special phenomenon in meteorology. In subtropics, if there is a huge heat source on the ground, it heats the air, making the lower air form cyclone circulation, while the upper air forms anticyclone circulation; In this way, there will be upward movement in the east, forming clouds and then precipitation, and downward movement in the west, forming dry and warm weather. This is called thermal adaptation. The Qinghai-Tibet Plateau is located in the troposphere, with an average elevation of 4000 meters. Due to thermal adaptation, water vapor and pollutants in the lower layer will "jump" to the upper troposphere and even reach the stratosphere with pumping. This is not easy to happen in other places.

In the direction of Nepal, the slope of the Qinghai-Tibet Plateau is extremely steep. The flat land in the south is only a few hundred meters high, and then the altitude rises sharply, from not far from the sea level to the upper troposphere. Such a large slope makes it have a great heating effect on the air.

Why is this heating so important? This should start with precipitation. The distribution of water vapor in the atmosphere is very special, and 85% of water vapor is concentrated in the atmosphere 3 kilometers near the ground. Clouds and precipitation are mostly formed in the atmosphere above 3 km. This pumping action on the Qinghai-Tibet Plateau will transport water vapor to the upper air. Because of heating, water vapor will "climb up" along the southern slope of the plateau, forming clouds and forming precipitation.

How does the Qinghai-Tibet Plateau play the role of "sensible heat pump", thus affecting the monsoon climate in China? The thermal conditions of the ocean and the mainland are different. It is conceivable that in summer, we will feel hot when we step barefoot on rocks in the sun. In winter, we will feel cold when we step barefoot on the stone that has been irradiated by the sun, because the heat storage and release capacity of the stone (that is, thermal inertia) is very low. Because of the large thermal inertia of seawater, it can store heat when the solar radiation is strong, and release heat when the solar radiation energy is weak, so the seawater changes little in winter and summer. This is the temperature difference between land and sea. The air near the ground runs from a cold place to a hot place, because the air pressure in a cold place is high and that in a warm place is low. This has formed a prevailing wind with completely opposite directions in winter and summer, which brings obvious weather and climate changes in winter and summer to China, and we call it monsoon.

In winter, the Qinghai-Tibet Plateau blocks the low-level westerly airflow in China, which is divided into two branches, the south and the north, and the north branch flows to the Pacific Ocean through northwest, north, northeast and east China. After flowing through the south side of the Qinghai-Tibet Plateau, the south branch airflow turns into a southwest airflow with high temperature and humidity, which affects Sichuan, Guizhou, Yunnan, South China and the middle and lower reaches of the Yangtze River in China. These two air currents finally converge near the east longitude 1 10 of the Qinghai-Tibet Plateau, and the wind speed increases, which will form the westerly jet.

1957, Mr. Ye Duzheng and his collaborators put forward for the first time in the world the phenomenon that the thermal action of the Qinghai-Tibet Plateau will affect the global climate, and established the meteorology of the Qinghai-Tibet Plateau. After Mr. Ye Duzheng discovered this phenomenon, Chinese meteorologists have done a lot of research on the sensible heat pump effect on the Qinghai-Tibet Plateau. In the model, they heated, partially heated and unheated the terrain of the Qinghai-Tibet Plateau to simulate the surrounding wind field and vertical wind field. The simulation test shows that when the Qinghai-Tibet Plateau is completely heated, the air in the surrounding areas (Arabian Sea and Bay of Bengal) will flow to the plateau, increasing the upward movement and forming convergence. When the top of the plateau is not heated and the side is heated, the surrounding atmosphere can still be pumped to the plateau, forming a strong upward movement, while the unheated top has no upward movement; When only the top of the plateau is heated, the ascending motion only occurs at the top, and the surrounding atmosphere is not affected. Due to the heating of the plateau side, the lower atmosphere will move upward with water vapor, forming clouds and precipitation. This is the heating pump effect on the Qinghai-Tibet Plateau.

In summer, there is a South Asian high over Eurasia from 10 km to 16 km, which is the strongest high on the earth in summer. According to observation and statistics, the South Asia High Center appears either over the Qinghai-Tibet Plateau or over the Iranian Plateau. Scientists such as Mr. Tao Shiyan found that when the location of the South Asian High appears in the east and west directions respectively, the precipitation distribution is also different: if the South Asian High appears over the Iranian Plateau, there will be less rain in eastern China and Japan, and more rain in southern Qinghai-Tibet Plateau and northern India; If it appears over the Qinghai-Tibet Plateau, there will be less rain in southern Qinghai-Tibet Plateau and northern India, and more rain in eastern China and Japan. This change of the center position of the South Asian High is mainly caused by the change of the heating effect of the Qinghai-Tibet Plateau. After the abnormal high center is formed, it moves to the west and gradually disappears. After a period of time, a new abnormal high center will be generated, and then it will move westward, so quasi-biweekly oscillation will be repeated, so it will rain in the next period of summer in China and rain in the next period. This is the influence of the interaction between the Qinghai-Tibet Plateau and the ocean on short-term climate change.

Everyone knows the El Nino phenomenon and La Nina phenomenon. In El Nino, the summer monsoon broke out late, because the ocean is too warm, and it is too difficult to change the land-sea state into a summer type with cold south and warm north. If it is La Nina year, the sea water is already very cold, and it is easier to become summer type. This is the influence of Qinghai-Tibet Plateau and ocean on interannual climate change.

So what is the relationship between the Qinghai-Tibet Plateau and interdecadal climate change? The study on the precipitation distribution in China and the thermal effect of the Qinghai-Tibet Plateau from 1950s to the beginning of this century shows that when the thermal effect of the Qinghai-Tibet Plateau weakened year by year from 1980s to the end of this century, the rain belt in eastern China gradually moved southward, and the south was flooded and the north was dry. From the end of 1990s to the beginning of this century, the thermal effect of the Qinghai-Tibet Plateau gradually increased in summer, and the rain belt in eastern China gradually moved northward in summer. There is a certain causal relationship between the two.

With the deepening of the research on the Qinghai-Tibet Plateau, we find that there are too few observation data on the Qinghai-Tibet Plateau. Therefore, starting from this year, China Meteorological Bureau plans to increase meteorological and climatic observation points on the plateau in ten years, in conjunction with neighboring provinces of the Qinghai-Tibet Plateau, bringing the number of national ground meteorological observation stations to 453, regional automatic meteorological observation stations to 6,754 and soil moisture observation stations to 460. Not only that, but also vigorously develop Fengyun series meteorological satellites to enhance the space-based observation capability of the Qinghai-Tibet Plateau. In line with this, the National Natural Science Foundation of China also demonstrated, approved and launched a ten-year major research plan "Changes of the Earth-atmosphere Coupling System on the Qinghai-Tibet Plateau and its Global Climate Effects" on 20 13. These measures will effectively promote the research progress of the Qinghai-Tibet Plateau and improve the ability of weather and climate prediction.

Qinghai-Tibet Plateau is an important factor to control atmospheric circulation, which affects regional and global climate and its changes through global energy and water circulation. In the future, meteorologists will make full use of the newly-built meteorological research-operational comprehensive exploration of the plateau and its surrounding areas, understand the coupling process between the earth and the atmosphere, the process of cloud precipitation and water circulation, and the process of troposphere-stratosphere interaction, establish the database and assimilation system of the Qinghai-Tibet Plateau, improve the numerical model of the regional and global climate system of the Qinghai-Tibet Plateau, reveal the mechanism of energy and water cycle of the Qinghai-Tibet Plateau, and further push the atmospheric scientific research of the Qinghai-Tibet Plateau in China to the world stage and walk in the forefront of the world.