Climate and vegetation zones
Climate and vegetation zones
Weather and climate vary a lot over the planet. In certain places, it's always warm. Swimming weather all year round. In other places though, it's skiing weather all year round. It's cold.
Sometimes very cold. Some places are dry. Others are rainy and wet. What is it that decides this? Most importantly it's the sunbeams as they hit the surface of the earth.
This beam of sunlight reaches the earth close to the equator. It hits a small area, where it gets hot. Here, close to the poles, each beam of sunlight is spread out over a much larger area, which is not heated as much. This way, the climate becomes warmer the closer to the equator you are. We'll take a journey on the earth, from the equator to the north pole, to see what different climates we encounter on the way from warm to cold.
We start in the Congo, in central Africa. Here we are close to the equator. The sun shines intensely. It gets very hot. When the air gets warm, it becomes lighter and moves higher up in the atmosphere.
The water vapour in the air goes with it. Higher up, the air gets cooler. The water vapour becomes small droplets. It starts to rain, which it does almost every day. So, near the equator it's not only warm, it's humid too.
The forests are green and dense, and are called rainforests. Now we move north from the equator. Large plain areas spread out. The vegetation is tall grass, and scattered bushes and trees. The climate is dryer here, but rain comes in vast amounts during certain periods of the year, rain seasons.
This is the savannah. Between them, the rainforests and the savannah make up the tropical climate zone. Now we continue further north. The sun is blazing. Here it is extremely hot, and almost nothing grows.
It is a desert. How come it's so dry here? Do you remember that the air rises from the equator when the sun shines, and it gets hot? That air can't rise forever. When it has reached a certain height in the atmosphere, it moves south, or north instead.
After a while, it becomes so cool and heavy it starts to sink toward the earth again. Then, lots of air is pressed to the earth, and high pressure areas are created. The weather becomes dry, and warm, such as in the Sahara Desert. A little further north, we reach the Mediterranean. Here, it is dry and very warm in the summer, while the winters are mild and bring more precipitation.
This climate zone, with dry, hot and long summers, and a short mild winter, is called the subtropical zone. Further north, it's cooler again. Here we have four distinct seasons. Spring, summer, autumn, and winter. The vegetation is primarily woodland.
Broadleaf or pine trees. A giant belt of pine forests spread, from Scandinavia, over Asia, and all the way across the North American continent. This is the temperate climate zone. We finish our journey in the very north. It's cold, all year round.
There are areas here, where the ice melts in the summer and allows for a little vegetation to grow, but in the extreme north, the ice is there all year round. This is the polar climate zone. We started our journey in Africa and travelled north, through Europe to the North Pole, but it looks about the same if we make a similar journey, from the equator to one of the poles, in other parts of the World. And therefore we can divide the earth into four climate zones. Closest to the equator, there is the tropical zone.
It's warm the whole year round and rains a lot. Some distance from the equator, there is the subtropical zone, with a dry and hot summer, and a short, mild winter. The temperate zone has four distinct seasons, and large forests. And in the polar zone, it's cold, with almost no vegetation.