What is monsoon climate?

Monsoon climate refers to the regional climate dominated by monsoon, which is a mixture of continental climate and maritime climate. Summer is affected by the warm and humid air current in the ocean, which is hot, humid and rainy, and the climate is maritime. In winter, affected by the dry and cold air currents in the mainland, the climate is cold, dry and rainy, which belongs to the continental climate.

Formation of monsoon climate:

The role of monsoon system is to drive the atmospheric exchange between the southern hemisphere and the northern hemisphere, so it has large-scale characteristics and brings abundant precipitation to its affected areas. The formation of monsoon circulation has its specific geographical background and thermal conditions, and its fundamental driving factor is the seasonal variation of solar radiation and its embodiment in atmospheric circulation.

1, sea-land temperature difference

The seasonal variation of sea-land pressure and wind direction caused by the thermal difference between sea and land is different from the daily variation of sea-land wind. Although both of them are caused by the thermal difference between land and sea, the spatial scale and period of the former are much larger than that of the land-sea wind.

Sea-land wind is the diurnal wind direction change caused by the diurnal variation of air pressure in coastal areas, which takes one day as a cycle and is confined to limited coastal areas. The conversion cycle between monsoon wind direction and air pressure field is continental cold high pressure in winter, ocean hot low pressure in summer and ocean high pressure cold source. Therefore, the seasonal variation of land-sea thermal action is closely related to the evolution of monsoon.

2. Seasonal movement of the position of the planetary wind belt

The seasonal changes of solar radiation, temperature and air pressure lead to the seasonal movement of the whole atmospheric circulation field from north to south in summer, so the obvious seasonal changes of wind direction-monsoon phenomenon, such as the seasonal transformation of trade winds, show very obvious periodic seasonal alternation in low latitudes. At low latitudes, it is easterly in winter and westerly in summer.

3. The influence of topography on monsoon circulation.

There are also seasonal thermal differences between the huge and towering terrain, such as the Qinghai-Tibet Plateau and the surrounding free atmosphere. In winter, the plateau is the cold source, and a cold high pressure forms in the lower part of the plateau, where anticyclonic circulation prevails, and the northeast-north wind prevails in the southeast. In summer, the plateau is the heat source, and a thermal depression is formed in the lower layer, and cyclone circulation prevails. Southwest wind appears on the east side of the plateau, which strengthens the southwest wind in summer.

Due to the global land and sea distribution, the movement law of planetary wind system and the action of large terrain, there are large-scale seasonal changes of pressure field and wind field in some specific areas, accompanied by seasonal changes of precipitation. These areas are called monsoon areas.

Extended data:

Characteristics of monsoon climate in China;

China is located in the southeast of Eurasia, the largest continent on earth. In winter, the Asian continent is the source of cold air, forming a cold high pressure, and the cold air diverges from the mainland to the periphery; In summer, the land heats up rapidly, forming a hot low pressure, and warm and humid air blows from Zhou Haiyang to the center of the low pressure. This change in the prevailing wind direction, which is opposite in winter and summer, has brought about obvious seasonal changes in the climate, and this change has formed the monsoon climate in China.

The cold high pressure on the winter monsoon continent was formed in September, and its center is located in Mongolia. The cold and dry northwest or northeast monsoon blows out, first reaching the north of China, and then rapidly advancing southward to the Jianghuai Basin and its south area. The winter wind intensifies month by month with the change of seasons, and it is strongest in 5438+1October and June. Every 7 ~ 10 days, cold air bursts southward, and the temperature in South China can be reduced by 12 ~ 16℃ for 24 hours, sometimes accompanied by moderate to heavy rain.

When the winter wind is strong, it can blow to northern Australia, which is the southernmost limit of the winter wind. Cold and warm air in the northern and southern hemispheres is often mixed in this convergence zone or intertropical convergence zone. At this time, the winter wind blowing from the Asian continent meets the cool and humid airflow blowing from the western Pacific subtropical high, forming a north-south convergence line, and these convergence zones are rich in precipitation.

Winter winds only prevail at low altitudes (below 3,000m). The average altitude of the Qinghai-Tibet Plateau in southwest China is above 4,000m, so it is difficult for cold air to cross the Qinghai-Tibet Plateau. Winter winds flow to the eastern part of China along the eastern side of the Plateau and its east.

Cold air often goes south with the cold front, and the north is sunny and sunny, and slowly runs to Jianghuai and its south; The Yunnan-Guizhou Plateau often forms a stationary front, which shows a wide range of rainy weather.

In April and May of the summer monsoon, the Asian continent heats up rapidly, forming a thermal depression, the center of which is located in the western part of the Qinghai-Tibet Plateau. However, the warm and humid airflow dispersed by the Pacific subtropical high goes deep into the north and Hetao area from the southeast coast in the form of southeast or south monsoon, and its climate is characterized by hot and humid and thunderstorms.

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