Related knowledge of cyclone

Cyclone refers to a large vortex in which the horizontal airflow in the northern (southern) hemisphere rotates counterclockwise (clockwise). At the same height, the air pressure in the center of the cyclone is lower than that around it, which is also called low pressure. It appears as a low-pressure area surrounded by closed isobars on the contour map, and a low-value area surrounded by closed isobars on the contour map. Cyclones are similar to circles or ellipses, and their sizes vary greatly. Small cyclones have a horizontal scale of several hundred kilometers, and the large ones can reach three or four thousand kilometers, which belongs to the weather scale weather system. In cyclones, the weather often changes dramatically, which is the weather system that people are most concerned about and studied at the earliest.

There are all kinds of eddies in the atmosphere, similar to those in rivers. Some of them rotate counterclockwise and some rotate clockwise. Among them, the larger horizontal vortex is called cyclone and anticyclone respectively, that is, low pressure and high pressure. Cyclone, in the northern hemisphere, the air moves counterclockwise, the central air pressure is the lowest, and it gradually increases outward, and the air continuously flows into the center, forming an updraft, also known as low air pressure. Its diameter: tens of kilometers small, thousands of kilometers big. When affected by hurricanes, rainy weather and strong winds often occur. The center of cyclone is cloudy and rainy because of updraft, and it is usually surrounded by downdraft, which is easy to dry and sunny, so is the familiar typhoon.

Let's first look at the formation of frontal cyclone from the knowledge of frontal and cyclone. The front is the interface formed by the intersection of cold and warm air, and it is a narrow and inclined transition zone. Cyclones are low pressure. In the northern hemisphere, it is a weather system in which air flows counterclockwise from the periphery to the center. Frontal cyclones generally appear in places where isobars are irregular ellipses.

As shown in the figure, this is a low pressure area. According to the wind map of the northern hemisphere, it can be determined that the south wind blows in the east and the north wind blows in the west. The narrow area where low pressure extends outward is called low pressure trough, just like the valley on the terrain. AB and CD are two slot lines in the figure.

Fronts are usually formed in the trough of low pressure of surface cyclones. In the picture, the southerly wind to the east of the cyclone comes from lower latitude and the temperature is higher. When moving northward, it meets cold air at higher latitudes, forming a warm front (near CD in the picture). Similarly, the airflow in the west of the cyclone comes from the northerly wind at high latitude in the north, and it will meet warm air at low latitude in the south to form a cold front (near AB in the figure), thus forming a frontal cyclone in the surface weather system. The cyclone in the northern hemisphere is a vortex that flows counterclockwise, and it also moves counterclockwise with the generated front.