What are the effects of subtropical high on China? How does it affect the weather in our country?

The Impact of Subtropical High on China Subtropical High refers to a warm and high pressure system located in the subtropical region. In the subtropical region of the northern and southern hemispheres, due to the influence of land and ocean, the high pressure area is often divided into several high pressure units, forming a discontinuous high pressure area distributed along the latitude circle, which is collectively called subtropical high. Subtropical high is mainly located in the ocean and exists all the year round. According to different geographical locations, they are called North Pacific High, North Atlantic High, South Pacific High, South Atlantic High and South Indian Ocean High respectively. Subtropical high can also be divided into smaller high-pressure cells, and some small cells can also be located on the mainland. For example, the monomer located in the South China Sea in winter is called the South China Sea High.

As for the subtropical high, the vertical motion of the atmosphere between the east and the west is quite different: in the east of the high, the sinking motion is particularly strong, and the downward airflow is warmed by adiabatic compression, resulting in a strong subsidence inversion, which is called trade wind inversion. This strong inversion stratification is very stable, which inhibits the development of vertical convection, makes the weather continue to be fine, and forms a dry climate zone on the west coast of subtropical continent.

The western part of subtropical high is the convergence and rising area of low-level warm and humid air, which is prone to thunderstorm weather. With the change of seasons, the intensity and location of subtropical high will also change obviously between seasons. From June to July, 65438, the main body of subtropical high in the northern hemisphere moved northward and westward, and its intensity increased. In July-65438+10, the main body of the subtropical high moved from south to east, and its intensity weakened. This seasonal change also has obvious stages of slow change and sudden change.

Main impacts:

The warm high which has an important influence on the weather and climate in China is the western Pacific subtropical high. The position of the western Pacific subtropical high changes with the seasons, generally moving between10 ~ 40 N. In winter, the ridge line of the subtropical high is near15 N, and it moves slowly northward with the seasonal warming. In April and May, the ridge line of subtropical high was at15-20 N, and the polar front rain belt landed in South China in April. From May to mid-June in Nanling, the subtropical ridge line jumped northward for the first time, crossing 20 N and hovering between 20-25 N; The polar front rain belt reached the Yangtze River basin, forming plum rain, when South China turned into sunny, hot and dry summer. In the middle and late July, the subtropical high ridge jumped northward for the second time. The ridge line quickly jumps over 25 N, then swings between 25 N and 30 N. The rainy season in the middle and lower reaches of the Yangtze River ends and the hot and dry weather begins. The Huanghuai area entered the rainy season under the influence of the polar front rain belt, while the tropical cyclones and typhoons in South China entered the second flood season, that is, the "late flood season", due to the convergence of the equator to the north.

From the end of July to the beginning of August, the subtropical ridge jumped northward for the third time, crossed 30 N to reach the northernmost position and stayed there, and North China and Northeast China entered the rainy season. In late August, with the strong cold air moving southward, the subtropical high in the northwest Pacific weakened and the ridge line began to retreat rapidly from north to south. At the beginning of September, the ridge line retreated to about 25 N for the first time, and the weather in China changed from north to south to crisp in autumn. 10 year1early October, the subtropical ridge retreated to the south of 20 N, ending the seasonal north-south movement with a one-year cycle.

Subtropical high prevailing downdraft, sunny weather. When the subtropical high controls a certain area for a long time, it often causes drought in this area. The northern side of the western Pacific subtropical high is the mid-latitude westerly belt, which is also the location of the subtropical front. The southerly airflow on the west side of the subtropical high can bring rich water vapor from the sea surface and transport it to the lower layer of the front, forming a warm and humid conveyor belt in the edge area from the west side to the north side of the subtropical high, and continuously transporting high-temperature and high-humidity airflow to the front area on the north side of the subtropical high.

When the west wind moves through the front area in a trough or vortex, rich water vapor condenses under the combined action of the ascending motion of the system caused by unstable energy release, resulting in a wide range of precipitation and rain belts, usually accompanied by heavy rain. According to statistics, the position of rain belt is generally 6 ~ 10 latitude north of the ridge line of subtropical high, and its trend is roughly parallel to the ridge line.

The position of subtropical high is closely related to the position of rain belt, so the abnormal change of subtropical high will often cause drought and flood disasters in various regions, such as 1954, 1980, 199 1 year, where the ridge of subtropical high hovers for 20 ~ 25 N for a long time, and the rain belt is stable in the Jianghuai basin, resulting in Jianghuai. However, in 1978 and 1983, the ridge line of subtropical high quickly crossed 20 ~ 25 N, reaching about 30 N, and the rain belt basically did not stabilize in the Jianghuai basin for a period of time, and the Jianghuai area was under the control of subtropical high for a long time, resulting in drought in this area.