Extreme weather conditions like heavy rains, heavy storms, hurricanes, tornadoes, and at the same time, lack of rain or heat waves causing droughts can result in situations that endanger human life – e.g., in form of flooding or drought causing famines.
A hurricane, tropical cyclone or typhoon is a kind of storm system fueled by the heat released when moist air rises and condenses, with a closed circulation around a centre of low pressure.
The key characteristic of a hurricane is that it has warm water as a heat source, with a minimum water temperature of 26.5°C, until a depth of 40 m is reached. Water evaporates from the ocean and rises upwards, where it condensates to rain down. The air flowing out on top of this chimney flows downwards again, where it can, added with air from the side, fill in the low pressure gap, and rise again.
The cyclone keeps spinning through the Coriolis effect, caused by the rotation of the earth. Along the equator, cyclones do not occur because the Coriolis force isn’t strong enough. Water that is warm enough is only found in tropical oceans. Reaching land, they soon die down. Damages are caused by the enormous storm rain-falls and flood-waves caused.
The terms vary only to the geographic location. A hurricane occurs in the northern Atlantic and northern and southern Pacific (in the Caribbean), a Cyclone in the Indian Ocean, and a Taifun in the north-western Pacific (around China and Japan).
A tornado is a violently rotating column of air which is in contact both with a cloud base and the surface of the air. They can rotate with a speed of up to 180 km/h, can be 75m across, and can travel several kilometers before resolving.
A flood defines a sudden rise in water to cover land that is not usually covered by water. This land will be suddenly covered by significant amounts of water, caused either by the tides of the ocean, rivers, enormous rain-fall or snow-melt.
Sea storms or tsunamis can cause flooding by oceans, heavy rains or even snow-melt caused by heat waves and can arouse a sudden swell of rivers. Even geological events like earthquakes and volcanic eruptions can result in flooding.
Regular flooding can be integrated into agricultural traditions by identifying areas open to flooding on purpose, as the flooding produces furtive farm land. Flooding on land becomes a disaster when it reaches extraordinary scales and effects human culture, e.g., settlements that are too close to the river. Systems of protection against flooding have been developed developed such as, system of dikes, river regulations, and by forecasting by satellite data.
Heat waves, which are defined by more than three days of unusually hot weather in relation to the regional average, e.g., in Europe more than 30°C, in Australia more than 40 °C. The European heat wave of 2003 caused the death of 50.000 people, and led to shortfalls in the wheat harvest of up to 75-80%, in Ukraine and Moldavia, hindered shipping on dried out rivers like the Danube, and by melting glaciers in the Alps that caused flash floods and avalanches.