Weather's Building Blocks The weight of the air molecules above causes air pressure. Even small air molecules have weight, and the massive quantities of air molecules that make up our atmosphere's layers together have a lot of weight, which bears down on whatever lies below.
The Earth's Surface is Flattened By the weight of the atmosphere, the Earth's surface is flattened at the poles but raised in the middle. This is why maps show places like Poland and India to be larger than they actually are; they're just balls of dirt with mountains on them. But the real reason the ground there is flat is because it's covered by rock that's very dense compared to water.
At the Poles, There Is No Dirt For something to be flat, it can't be moving. So at the top of every man-made mountain, such as Mount Everest, there is simply nothing beneath your feet. The weight of all the air above you is holding you up, so you must be floating in space.
Air Pressure & Weather Forecasts Air pressure measures how much force is pushing down on an object with each square inch of area. It is used to estimate how heavy the air is, which is important for weather forecasts.
Low air pressure occurs when there is a lack of wind causing clouds to form and remain over one area.
The weight of the air molecules above causes air pressure. Because of this pressure, air molecules at the Earth's surface are more closely packed together than those higher in the atmosphere. This means that there is a greater number of particles per unit volume closer to the ground.
This increased density of particles near the ground creates what is known as an "air mass". Air masses are characterized by their physical and chemical properties which result from their having been wrapped in plastic during transportation to high altitudes where they become aerosols (i.e., small solid or liquid particles suspended in gas). The different effects caused by these masses of plastic-wrapped air travel across large distances, influencing weather conditions far away from where they were made.
For example, air masses can be classified by their effect on temperature. If one travels into a cold air mass, then one will feel cooler because there are more particles around to reflect heat away from the body. If one travels into a hot air mass, then one will feel warmer because there are more particles around to absorb heat from the body.
Air masses can also be classified by their effect on precipitation. If one travels into a cloud chamber, then one will see clouds form because water particles in the air mass have combined with oxygen molecules to create droplets of water.
It is, nevertheless, in charge of keeping the world habitable and creating weather. Gravity holds the atmosphere around the Earth. Gravity attracts gas molecules in the atmosphere to the Earth's surface, resulting in air pressure. The force with which air molecules push on a surface is measured as air pressure. At sea level, this pressure is about 1 kilopascal (kPa), but it can be as high as 10 kPa or more near mountain peaks.
Gravity also pulls gas particles toward the center of the Earth, so there are less particles in the upper part of the atmosphere and more down below. This is why heights affect wind patterns: As you go up, there's less air above you, so winds tend to flow downward. Downward-moving winds are called "trade winds." Upward-moving winds are called "foehn" or "chinook" winds.
The Earth's rotation causes dry air to move away from regions of low pressure, causing highs and lows to develop. These movements of air cause the earth's weather.
High pressure systems are gray areas of clouds and stable conditions while low pressure systems are white holes with wind and rain. The direction of maximum atmospheric pressure is indicated by the anemometer symbol, which points up in the Northern Hemisphere and down in the Southern Hemisphere.
The amount of water vapor in the atmosphere is one factor that affects air pressure.
Gravity drives gas molecules in the atmosphere toward the Earth's surface, resulting in air pressure. At sea level, this pressure is about 1 kilopascal (kPa), but at high altitudes it can be much lower. The higher the altitude, the lower the pressure; at the top of our atmosphere, there is only 0.5 kPa of pressure left over from when gravity pulled all the air away.
The atmosphere contains almost everything in earth's crust. It consists of 78% oxygen, 20% nitrogen, 1% argon, and less than 1% other gases. The remaining percentage is empty space.
Oceans cover 70% of the earth's surface, and most of that water is 100 degrees F or warmer. Only 3% of the ocean water is between 5 and 25 degrees C. Even though the ocean covers half the planet, it contains only 10% of the world's water supply. The rest is land ice (which will one day melt).
The atmosphere protects us from many dangers including solar radiation, cosmic rays, and toxic chemicals. It also gives us food by allowing plants to grow and animals to reproduce. Without air, none of these things could happen.
Air pressure falls when one rises higher in the atmosphere. There is less pressure from the weight of the air above because there are fewer air molecules above. The pressure at the Earth's surface, the bottom of the atmosphere, fluctuates from day to day. Because heated air rises, pressure is generally lower in areas where the air has been warmed. In general, as one goes up into the atmosphere, the pressure decreases.
In conclusion, air pressure decreases with height above ground level (AGL). This is because there is less air density (number of particles per unit volume) at high altitudes. As well, at high temperatures, air expands, which makes it lighter and so less dense.
Lower air pressure means that humans and animals living at those heights experience greater levels of stress from weather events like hurricanes and tornadoes. Also, astronauts living in space vehicles outside the protective influence of a planet have their internal air pressures reduced due to lack of gravity. This can lead to other health problems for these individuals as well.