వాతావరణ పీడనం అంటే ఏమిటి?
Photo: Are you feeling under pressure? It's caused by the weight of a column of air (mostly molecules of nitrogen and oxygen) pressing down on you. The higher up you go, the "thinner" the air gets (the fewer the air molecules) and the less the pressure.
If you've ever been scuba diving, you'll know just what pressure feels like. Dive down beneath the surface of the sea and you'll soon feel the weight of water pressing in on you. The deeper you go, the more water there is above you, the more it weighs, and the more pressure you feel. But there's pressure pushing in on your body even if you never go in the sea.
Look up at the sky and try to imagine the weight of the atmosphere: the huge amount of gas surrounding our planet and pulled to its surface by gravity. All that gas might look like a vast, empty cloud of nothing, but it still has weight. And it still presses down on your body. That's air pressure. When you're under the sea, the weight of water pressing in on your body makes it hard to breathe from your oxygen tank. Air pressure never has this effect because our bodies are hollow and our lungs are full of air, so the air presses equally on the inside and outside of our body at the same time. That's why we don't feel air pressure in the same way we feel water pressure.
Why air pressure changes from place to place
Air pressure varies all across our planet. It's highest at sea level (where there's the most amount of air pushing down) and gets lower the higher up you go. Way up in the atmosphere, there's much less air—so there's less oxygen to breathe. That's why mountain climbers often have to use oxygen cylinders. It's also why airplanes have to have pressurized cabins (internal passenger compartments, where the air is kept at higher pressure than it would normally be at that altitude) so people can breathe comfortably.
Even in one place, the air pressure is constantly changing. That's because Earth is constantly spinning and moving round the Sun, so different parts are being warmed up by different amounts. When the air cools and falls, it increases the pressure nearer to the ground. Regions of high pressure like this are linked with fine weather. The opposite happens when the air warms and rises to create regions of low pressure and wet weather.
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