The typhoons that affect China are mainly from the Pacific Ocean
east of the Philippines, and sometimes also from the south China
sea. Near the equator, the sea is hot, the evaporation is intense,
a large amount of rising air is hot and humid, drawing the cold
air around to take the place.
Because of the earth's rotation, the air in the northern hemisphere
deflects to the right, and the cooler air coming from all sides moves
towards the areas where hot and humid air is rising. The deflection
to the right creates an air vortex over the ocean. This vortex moves
counterclockwise and is called a cyclone. If the process of forming a
vortex is repeated, the cyclone will rotate faster and wider. If the
wind near the center of the cyclone reaches force 8 or above, it is
called a typhoon.
The diameter of this huge air vortex ranges from several hundred kilometers
to thousands of kilometers, and the height is above eight or nine kilometers.
The central part is called the typhoon eye, with a diameter of 10000m to
56000m. It is surrounded by rapidly rotating air currents that form huge,
thick walls of clouds, or cloud walls.
In the eye of the typhoon, the air pressure is low with slow wind and high
waves because the air outside can not flow in. When the clouds are separated
and thinner, the sun and moon stars are visible sometimes. But around the
eye of the typhoon is the most stormy region.
Due to the guidance of the upper east wind flow and the impact of the
earth's rotation, the typhoon tends to move west and north after its
formation. So in China, Taiwan and southeast coastal areas bear the brunt.
When the typhoon is over land, its heat and water can’t be replenished,
and the friction with the ground decreases its speed, thus he impact
of typhoons is limited to coastal areas and has no direct impact on
The formation of typhoons is observable, especially with advanced
meteorological observation means. According to satellite photos,
researchers can know everything about the formation process, moving
route and running speed of typhoons. Therefore, the meteorological
department can make an accurate forecast of the typhoon at present.
With the forecast, people can make full preparations in advance to
avoid or reduce the damage typhoons caused.