A tropical cyclone can form over land

Video: How does a tropical cyclone form?

Tropical cyclones occur over the oceans through the evaporation of warm sea water with the help of the Coriolis force. They reach wind speeds of up to 250 kilometers per hour and often cause floods and storm surges.

Tropical cyclones form over the oceans

Whether hurricane, typhoon or cyclone - despite their different names in different parts of the world, tropical cyclones have one thing in common: The storms occur in the tropics over the oceans. Sea water evaporates in the process, so that warm, humid air can rise quickly to the top. Violent hurricanes can cause damage amounting to millions and, with their enormous destructive power, often claim many deaths, especially in the tropical coastal regions.

Tropical cyclones are dependent on water temperature and Coriolis force

Tropical cyclones can only arise under very specific conditions. To do this, the temperature of the sea surface must be at least 27 degrees Celsius and the Coriolis force must play a role. The Coriolis force is generated by the rotation of the earth and deflects the air masses: in the northern hemisphere to the right, i.e. to the east, in the southern hemisphere to the left, i.e. to the west. If these factors - warm sea water and Coriolis force - come together, under certain conditions a cyclone can develop. But this only works within the tropical zone on both hemispheres - between the 5th and 20th parallel. At the equator itself, the oceans are warm enough, but the Coriolis force is missing. At the poles it is the other way round: Here the Coriolis force is strong, but the sea water is too cold.

Cyclones are caused by evaporation on the sea surface

A tropical cyclone always arises in the same way: First, water evaporates on the surface of the sea, the warm, humid air rises and condenses in the height. The condensation creates cumulus clouds which, with their heat of evaporation, provide energy for the storm. The result: The wind speed increases, thunderstorm clouds are formed that are arranged in a ring and begin to rotate due to the Coriolis force. This spiral shape of a hurricane is also known as an eyewall - this is where the highest wind speeds and the heaviest precipitation occur. The rotating air masses can reach up to 250 kilometers per hour. In the center of the storm, in the so-called eye, on the other hand, there is almost no wind. There is a negative pressure here, through which warm, moist sea air is sucked in. This rises spirally into the eyewall and provides further energy for the cyclone.

Consequences of tropical cyclones

Tropical cyclones develop destructive forces with increasing strength. At sea they cause rough seas and endanger shipping. On land, hurricanes, typhoons and the like destroy buildings, roads and ports with their enormous wind speeds. In addition, there is often damage from heavy rain, floods and storm surges on the coasts. Fortunately, nowadays, with the help of weather satellites and the latest technology, it is possible to precisely determine tropical cyclones and their migration path and to warn the population in good time.