What storm has an eye?


A hurricane is a huge, whirling circle of wind and rain. But in the centre of all this wind and rain, the air is calm. This calm hole is called the eye of the hurricane.



A hurricane begins over the ocean, near the equator, where the air is very hot, wet, and still. The heated air begins to rise and whirl around. As the great masses of the air rise up, towering rain clouds form.



The winds swirl faster in a giant circle around the centre of calm, warm air. The storm is called a hurricane when its winds are stronger than 119 kilometres per hour.



Some people in the path of a hurricane experience what seems like two storms. First, the front of the circle hits. The blowing wind and rushing rain sound like steady thunder.



After the front of the circle passes over, the eye of the hurricane arrives. The wind dies down. The rain stops. The air grows hot and still. It may take an hour or more for the eye to pass over. Then the back of the circle arrives. Once more, the wind blows and the rain pours. Finally, the hurricane passes, carrying the wind and rain to another place.



Picture Credit : Google


How hard is the Wind Blowing?


Wind has many different names, depending on how hard it is blowing. In this question, you will find out how to tell how hard the wind is blowing by watching what it does. And you will learn some of the names we give to the different speeds of wind.




  1. In calm air, smoke rises straight up. The wind is blowing less than 1.6 kilometres per hour.

  2. In a moderate breeze, small branches sway, and dust and paper blow about. Wind speed is 21 to 29 kilometres per hour.

  3. In a strong breeze, big branches sway, and umbrellas are difficult to use. Wind speed is 39 to 49 kilometres per hour.

  4. In a moderate gale, whole trees sway, and it is hard to walk against the wind. The wind speed is from 51 to 61 kilometres per hour.

  5. A fresh gale breaks twigs off trees and makes walking very difficult. Wind speed is 63 to 74 kilometres per hour.

  6. A strong gale can blow tiles off roofs and damage buildings. Wind speed is 76 to 87 kilometres per hour.

  7. A whole gale will uproot trees and often do much damage to buildings. Wind speed is 89 to 101 kilometres per hour.



Picture Credit : Google


How do you explain wind?


Wind



When the air seems calm, and you can’t feel a wind, it doesn’t mean that the wind has stopped blowing everywhere. There are always many winds keeping the air around the earth moving. In one place, there may be a soft breeze from the north. In another place, there may be strong gusts from the south.



Two different winds may blow near the same area at once. Near the ground, one wind may be pushing flags in one direction. But higher in the sky, another wind may be making the clouds scurry in another direction.



The fastest winds are high above the clouds, several kilometres up into the sky. These winds are called jet streams. Often, jet streams are connected. They form one huge, rushing river of wind that circles the earth, sometimes at speeds of more than 320 kilometres an hour. When an aeroplane takes off for a long trip, the pilot may fly into the jet stream because it can give the plane a powerful push.



Picture Credit : Google


What makes the wind blow?


The wind moves over the land. It sways the tall grass in meadows and rustles leaves on trees. It ruffles your hair. In a storm, it whirls and roars. Wind can change a cloudy day into a sunny one by pushing clouds along. Wind is moving air. And it is the sun that makes air move.



The earth spins around like a big top. As it spins, each part of the earth, in turn, comes into the sunlight. The sun’s light warms the earth, and the earth warms the air. The heat makes the molecules of gas in the air move faster and spread apart. This warm air rises up like a big, invisible cloud. It rises because warm air weighs less than cool air.



As the warm air rises, cool air from other places flows in to replace the warm air. This moving cool air is the wind. When you feel the wind blow, you are feeling the movement of cooler air pushing in to take the place of the warm air that rose up into the sky.



What happens to the warm air? It cools and then sinks back to the ground. There it takes the place of warmer air, and all the same changes happen over again!



Picture Credit : Google


What is air made of?


Air doesn’t seem to be made of anything. It has no colour, taste, or smell, and you can see right through it. But air is made up of things. It is made of many kinds of gases. And these gases are made up of tiny bits called molecules.



Actually, everything on the earth is made up of molecules. Solid things, such as plants, animals, and rocks, are made of molecules. So are liquids, such as water, and gases, such as the ones in air.



In solids, the molecules are packed close together and hardly move. In liquids, the molecules are further apart and move faster. In gases, the molecules are very far apart and zip about rapidly. That’s why gases are so light that you can’t see them.



For us, the most important gas in the air is oxygen. We breathe to get oxygen into our bodies. Almost every kind of animal and plant in the world must have oxygen, or it will die.



Only about one-fifth of the air is made up of oxygen. Most of the air - nearly four-fifths - is nitrogen. The rest of the air is made up of many different gases. Water vapour and dust float in the air, but they are not part of the air.



If air is just floating gases, why doesn’t it float away into space? Because the earth’s gravity pulls at the air just as it pulls at you. The air can no more float off into space than you can!