The tropical rainforest is hot, moist biome found near Earth's equator. The world's largest tropical rainforests are in South America, Africa, and Southeast Asia. Rainforest precipitation fluctuates from 60 to 160 inches and is fairly evenly distributed throughout the year. The combination of constant warmth and abundant moisture makes the tropical rainforest suitable environment for many plants and animals. Tropical rainforests contain the greatest biodiversity in the world. Over 15 million species of plants and animals live within this biome because of its tropical rainforest climate.
In an average year in a tropical rainforest, the climate is very humid because of all the rainfall, rainforest precipitation amounts to about 250 cm per year. The rainforest has lots of rain because it is very hot and wet. This tropical rainforest climate is found near the equator. That means that there is more direct sunlight hitting the land and sea there than anywhere else. The sun warms the land and sea and the water evaporates into the air. The warm air can hold a lot of water vapor. As the air rises, it cools. That means it can hold less water vapor. Then as warm meets cold, condensation takes place and the vapor forms droplets, and clouds form. The clouds then produce rain. Rainforest precipitation lasts more than ninety days a year and the strong sun usually shines between the storms. The water cycle repeats often along the equator.
The main plants in this biome are trees. A lot of the rainforest precipitation that falls on the rainforest never reaches the ground. It stays on the trees because the leaves act as a shield, and some rain never gets past the trees to the smaller plants and grounds below. Trees in this climate reach a height of more than 164 feet. They form a canopy. The forest floor is called understory. The canopy also keeps sunlight from reaching the plants in the understory. Between the canopy and understory is a lower canopy made up of smaller trees. These plants do receive some filtered sunlight.
The tropical rainforest is classified as "Af" meaning tropical forest. The ?A? is given to tropical climates that are moist for all months, which have average temperatures above 18 degrees Celsius. The ?f? stands for sufficient rainforest precipitation for all months. The average temperature of a rainforest is about 77° Fahrenheit. The rainforest is about the same temperature year round. The temperature never drops below 64° Fahrenheit. Rainforests are so hot because they are found near the equator. The closer to the equator you are, the more solar radiation there is. The more solar radiation there is, the hotter it is. Rainforest are never found in climates which have temperatures 32° Fahrenheit and below because the plant life will not be able to live because they aren't adapted to frost. All the plants will die out if the rain forest is cooler.
Sometimes this constancy of temperature and humidity leads people to argue that rainforests have no seasons, but in the tropics this is only partially correct. There may not be a cold winter and a hot summer, but there are dry seasons and wet seasons. Plants and trees flower at these different times of year, profoundly influencing the lives of the creatures who inhabit them. And our contemporary understanding of rainforests quickly dispels the misconception that this is a changeless Eden, where nature's endless bounty means things are always the same. In fact there's a constant fight for light, water and nutrients, one of the reasons natural selection has had such a powerful effect in creating the great numbers of species which make tropical rainforests the richest places for biodiversity on Earth.