سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 6872)

this leads to low pressure and rainfall. When the air reaches the edge of the atmosphere, it is unable to go any further and so it travels to the north and south. The air becomes cold and then falls, creating high pressure and dry conditions at around 30º north and south of the Equator. Large cells of air are created in this way. Air rises again at around 60º north and south and descends again around 90° north and south. (2) Global atmospheric circulation creates winds across the planet and leads to areas of high rainfall, like tropical rainforests, and areas of dry air, like deserts. Another example is a tropical cyclone which is a very powerful low-pressure weather system which results in strong winds (over 120 km/h) and heavy rainfall (up to 250 mum is one day). Tropical cyclones have different names depending on where they occur in the world. In the US and the Caribbean, they are known as hurricanes, in South Asia-cyclones, in East Asia-typhoons. What is the writer’s main purpose?