Trade winds and monsoon winds

Oh well. The wind took the ball out to sea. But why is it windy? What is making the air move? Close to the equator, the sun blazes.

The ground, and the air, become warm. And warm air rises upwards. So a void is created near the ground at the equator. The void must be filled with other air moving to replace it. And air that moves, is wind.

These particular winds blow toward the equator, from the north and from the south. But since the earth is spinning, the winds turn west. Winds of this type are called trade winds. They appear along the whole equator: over the land and over the sea. Sailors noticed early on that if you want to sail westbound, it is a good thing to do it near the equator.

Then you will have the trade winds behind you. Trade winds always blow in the same direction, all year round. From the east, to the west. They are easterly winds. But there is another type of wind, which changes direction depending on the season.

Here is another beach in another place. The wind is blowing from the land toward the sea. Why? Well, it’s the coolest time of the year. The land area, and the air above the land area is cooling down.

The water in the sea is not cooling down as quickly, and the air above the sea is therefore warmer than the air above the land. Just as we saw, the warmer air rises, and the air pressure lowers. Then the air above land starts to move toward the sea to even out the air pressure. Therefore it blows from the land toward the sea. But half a year later, during the warmest time of the year, the temperature over the land rises.

The land area, and the air above the land, now become warmer, so it’s here that the air rises and causes a low pressure. Therefore the cooler air starts to move from the sea to the land, which is in the other direction, compared to half a year ago. These winds: those that blow by the coast, and change direction with the seasons, are called monsoon winds. When it blows from the land the air is dry, and rain is sparse. This is the dry season.

But air coming in from the sea is moist. When it reaches the land it is cooled off, and the moisture in the air falls down as rain. Sometimes a lot of rain. This is the rainy season. - We’re catching up on it. We have the trade winds from the stern. - Aye aye, captain! - I have it!

I got it, Kim! - Look, a dolphin. - The ball, Philip! Hold on to the ball! - Where are we heading? - Apparently west. Again…