【正确答案】The diagram shows the life of a cyclone, a term from the South Pacific which means typhoon near the Philippines and hurricane around the Caribbean. It can be seen that the conditions required for a cyclone to form are determined by winds, water temperature, water depth and proximity to land and that there are also hemispheric differences.
Cyclones appear at least 500km from the equator and spin in a clockwise direction in the southern hemisphere whereas it is anti-clockwise in the northern. They can have a reach of up to 200km, travel at up to 20km per hour and have winds between 74-200 miles per hour. Yet the eye of a cyclone is actually quite calm and produces little wind. Ideally, for a cyclone to take shape, the water temperature of the sea should be at least 26.5 degrees Celsius and the water needs to be at least 50 metres deep. Under these conditions moisture is evaporated and at the same time fuelled by low altitude vertical winds to create a spiral effect which forms into a tropical cyclone. A cyclone will usually end when it crosses over land or travels in cooler waters.