Extratropical anticyclone, also known as extratropicalcold anticyclone (Cold high pressure) refers to the high pressure system generated and active in middle and high latitudes and temperate regions.Seen from the pressure field, the central pressure is higher than the surrounding pressure, and there is a high-pressure system with closed isobars.From the wind field, the wind rotates clockwise around the center of the high pressure in the high pressure area of the Northern Hemisphere.Therefore, it is also called anticyclone.Extratropical anticyclones are generally generated in high latitudes andCold air massComposition, moving south or southeast under the guidance of appropriate atmospheric circulation.It affects the middle and low latitudes and becomes a cold air activity.Sometimes the intensity of cold wave can be reached.Therefore, it is also called cold anticyclone.
The horizontal range of extratropical anticyclones generally reaches several thousand kilometers, sometimes occupying most of China.Its life history can be roughly divided into: initial stage, development stage and extinction stage.When an extratropical anticyclone moves from high latitude to southeast, its front often forms a cold front because it intersects with the warm air mass.Therefore, there are often cloud systems or wind and rain weather.However, when the cold front passes through and is controlled by the extratropical anticyclone, especially near the center of the anticyclone, it is mainly sunny weather.It often forms in winterfrost。
In the winter half year, the surface of the continent is cooled by intense radiation, and the air gathers on the continent to form a cold high pressure.The Mongolian Siberian high in East Asia is the most powerful cold high in the world. Its eastward movement is characterized by large-scale cold air activities, resulting in strong wind and cooling weather in the regions it passes.At the front edge of cold air and warm air, cloud and rain weather forms, and the main body of cold high pressure reaches the area to maintain sunny weather.
The Central Meteorological Administration has stipulated that if cold air invades during cold high pressure activities, the temperature will drop by more than 10 ℃ in 24 hours, and the minimum temperature will be below 5 ℃, accompanied by a northerly gale of about 6 levels, as the standard for issuing cold wave warnings.The national cold wave in winter half year in China averages 3-4 times a year.March to April of each year is the season with the most frequent cold wave activities, followed by November.The nationwide cold wave generally starts in late September and ends in May of the next year.It takes about 3-4 days for each cold wave to break out and end (move out of China).
Summer performance
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The cold air activity in summer cannot reach the cold wave standard, but there is still a 24-hour cooling of 10 ℃.In summer, the cold air moves to the southeast, forcing the warm air mass to rise, causing the water vapor to rise and condense into clouds, which is an important reason for the precipitation in eastern China.
