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What is cyclogenesis? What is the secret process behind low pressure areas?
In weather science, a low pressure area is a place where the atmospheric pressure is lower than the surrounding area. These low-pressure areas are often associated with severe weather, such as cloudy weather, strong winds, and possibly rain or storms. In contrast, areas of high pressure are associated with light winds and sunny weather. In the Northern Hemisphere, winds rotate counterclockwise around low pressure areas, while in the Southern Hemisphere they rotate clockwise due to Coriolis forces. The process of forming a low-pressure system is called cyclogenesis, which results in the divergence of winds in the upper atmosphere.
Cyclone formation is the process of development and intensification of low pressure areas, and is opposite to the reverse process of the formation of high pressure systems.
There are mostly two locations where cyclones are generated: one is on the east side of the wave trough flowing above, which forms a meteorological wave called Rossby wave. The second is a divergent region of wind embedded in front of shortwave waves, which have shorter wavelengths. When these winds diverge upward, they cause airflow in the troposphere to rise, causing surface pressure to drop. Thermal low pressure is caused by local heating of deserts and land caused by solar radiation. Locally warm air rises due to its low density, lowering the atmospheric pressure at the ground level.
When thermal low pressure forms over continents, it also promotes the formation of monsoon circulation.
In the tropics, an area of low pressure sometimes forms along with organized thundershower activity; this is called a monsoon trough in the tropics, especially when interacting with equatorial spreading belts. The monsoon trough reaches its highest point in the north in August and returns to the south in February.
The formation of tropical cyclones needs to meet some specific conditions, usually requiring the water temperature to be above 26.5 degrees Celsius in order to generate enough energy to drive convection. High humidity is also necessary, especially in the lower and middle layers of the airflow, as such humidity can promote the formation of unstable airflow.
Globally, tropical cyclone activity peaks in late summer, when the difference between warm and cold altitudes in the atmosphere is greatest.
The accompanying weather phenomena are also closely related to the low pressure system. When cold air from a high-pressure system rushes into a low-pressure area, this movement of air often speeds up the wind, creating strong winds. This is directly related to the pressure difference between high and low pressure systems. The greater the pressure difference, the stronger the wind speed.
During winter, the rapid cooling of the land creates a strong pressure difference with the slow cooling of the ocean, causing winds to blow from the ocean to the land. These phenomena all show the importance of low pressure areas in meteorological changes. Not only are they responsible for weather changes, they are also responsible for various climate patterns, including the effects of monsoons.
The operating patterns of low-pressure systems are closely related to a variety of factors, including topography, ocean temperatures, and changes in the atmosphere.
In mid-latitudes, large polar cyclones play a crucial role in the movement of weather systems. The presence of low pressure systems becomes increasingly evident in each region's seasonal changes. Especially in the winter, these low-pressure systems often bring dense precipitation.
Understanding the process of cyclone generation is not only the responsibility of meteorologists, but a topic that everyone should pay attention to, because it is related to our daily lives and the future direction of the climate. Have you ever thought about how these seemingly invisible changes in air pressure affect our lives and the environment?
