Storms get heavier

Storms

Hurricane, hurricane or typhoon?

If a wind has a speed higher than 74 kilometers per hour, it is called a storm. Storms are measured according to the Beaufort scale, which is named after the British Admiral Sir Francis Beaufort.

The scale ranges from 1 to 12, a storm with speeds of 75 to 88 kilometers per hour reaches Beaufort 9. From 117 kilometers per hour a storm is referred to as a hurricane, it reaches level 12 on the Beaufort scale.

Hurricanes

In general, a hurricane means wind speeds of at least 117 kilometers per hour. In the meantime, however, it has become established that the term hurricane is not used for tropical cyclones, but for strong storms over Central and Northern Europe.

Hurricanes roar across Central Europe, especially in autumn and winter. Then the temperature difference between the pole and the southern latitudes is particularly large. Cold air from the polar region meets warm air flowing from the direction of the equator. If these air masses meet, meteorologists speak of an occlusion - this can cause strong storms with hurricane strength.

Due to climate change, meteorologists have observed an increasing number of storms in Germany over the past few years and decades. Two striking examples of this were the hurricanes Lothar (December 26/27, 1999), which blew at around 180 kilometers per hour over southern Germany, and Kyrill (January 18, 2007), which even blew over large areas at up to 225 kilometers per hour Swept away northern Europe. Both are considered storms of the century and caused great damage.

Tropical cyclones: hurricane, typhoon, cyclone

Tropical cyclones arise over the sea. In the northern hemisphere they usually occur between June and November, in the southern hemisphere between December and May. Their designation is based on the region in which they were created.

Hurricanes are called tropical cyclones over the Atlantic, east of the West Indies and in the Caribbean. In the north-western part of the Pacific Ocean, in Asia, these are called cyclones Typhoons. These are called cyclones in the Bay of Bengal, in the Indian Ocean south of the equator and in the South Pacific Cyclones.

Cyclones occur over the sea when the water on the surface is at least 26 degrees Celsius and evaporates heavily. The humid air masses rise, the so-called Coriolis force creates a huge vortex, in the middle of which is the eye of the storm. There is absolutely no wind in the eye.

The moist sea air flows towards the eye and continues to rise there. It pulls cooler air with it, which then warms up. A fairly stable system forms in which very high wind speeds can arise. Around the eye, the air can travel up to 300 kilometers per hour.

As long as the cyclone stays above the sea and is supplied with enough moist air, it can last for up to two weeks. If it hits the coast at some point, it will run out of propulsion: the pent-up clouds will rain down and cool the land surface, warm air will no longer flow in, and the cyclone will dissolve.

However, the high wind speeds, coupled with heavy rainfall, can wreak havoc on land. They uproot trees, bring down houses, tidal waves flood entire areas of land.

Storm-free zone at the equator

The rotation of the earth causes the Coriolis force to act on the wind currents. Winds are deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This causes the air masses to swirl and cyclones can form. Directly at the equator, however, the Coriolis force is zero, so that the hot air can rise upwards.

Only from five degrees north and south is the Coriolis force strong enough that tropical cyclones can arise. Cyclones at the equator cannot be completely ruled out, but they cannot occur there.

Tornadoes

Tornadoes, which are also known as large currents or windpants, arise differently. They are mainly known in North America and occur locally. Tornadoes can occur when large storm clouds form over a layer of heated air. Then the cold air falls from a height of several kilometers, and a column of warm air screws upwards faster and faster.

The result is a trunk with extremely high speeds: more than 400 kilometers per hour have already been measured. Wherever the trunk meets the earth, it turns everything in the way into rubble and kindling. Houses collapse, vehicles are thrown through the air. Only a few meters away everything remains calm and undamaged.

Tornadoes also occur in Central Europe. On average, experts assume around 100 tornadoes per year in Germany. Around half are waterspouts on the coasts - because tornadoes can also form over the sea.

Early warning for storms

As a rule, satellites can detect tropical cyclones very early on. Nevertheless, it happens again and again that supposedly harmless low pressure areas are underestimated and suddenly develop a significantly higher destructive force than originally assumed. But even with early warning, storm damage is difficult to limit - often all that remains is to evacuate the affected areas.

Many scientists believe that the number and severity of hurricanes will increase as a result of climate change. Therefore, measures to protect the earth's atmosphere are becoming more and more important. At the same time, it is clear that a mere reduction in greenhouse gases is not enough.

It is already certain that people will also have to adapt to climate change. Research groups around the world are working to develop measures for this adaptation. These include, for example, better coastal protection with higher dykes and better drainage options in low-lying coastal regions.

In addition, these areas should not be used so intensively or not so densely populated. Protection against storm damage is also offered by adapted forestry, in which more resistant mixed forests are planted instead of monocultures.

Insurance companies are also sounding the alarm: According to the Munich reinsurance company, around half of the reported losses can be traced back to severe storms at hurricane strength. In the future, insurance companies could face too great a risk of covering the consequences of natural disasters.