In details

The winds


The moving air is called wind. Its direction and speed affect the weather conditions. To predict when an air mass will reach a particular location, it is essential to know the speed of the winds.

Air movement relative to the Earth's surface can range from calm and windlessness to the formation of hurricanes that cause wind destruction at more than 120 kilometers per hour.

Wind speed is measured with a device called anemometer, which is basically a type of weather vane, as shown below.

On the anemometer, the small shells spin when the wind hits them, making the whole piece spin. A pointer moves on a graduated scale where the wind speed is recorded.

At airports, it is common to see instruments such as windsock, which is very simple, used to check the wind direction. We can also find windsocks on beaches, to guide fishermen, surfers etc.

Airports currently have control towers, in which information on wind speed and direction obtained by instruments is processed by computers, which provide data necessary for landing and takeoff.

Now let's think: On warm days by the sea, a few hours after dawn, you can feel a pleasant breeze from the sea. How can we explain this?

The sun warms the sea water and the earth. But the earth warms faster than the sea. The heat of the earth warms the air just above it. This air gets warmer, less dense and rises. The atmospheric pressure in this region becomes lower than over the sea. As a result, the cooler, denser, and more pressure-laden mass of air over the sea takes the place of rising air. Then this air warms up, and the process repeats itself.

The horizontal movement of air from sea to land is called sea ​​breeze and it happens in the daytime.

At night the opposite happens: the earth cools faster than the sea, as water gains and loses heat more slowly than the earth. The air over the sea is warmer (the sea is releasing the heat accumulated during the day) and rising. Then the cold air of the earth moves to the sea. And the land breeze.