Because gravity pulls most gas molecules in the atmosphere close to the Earth's surface, gas particles are denser at the surface. More air is pressing down from above as the depth of the atmosphere increases. As a result, air pressure is highest at sea level and decreases with increasing height.
At any given point in an airplane flight cabin, the pressure outside the plane is always greater than the pressure inside the plane. This is because outside there is more space for the air to move around than inside where there is less room. As a result, people inside the plane feel lighter and balloons filled with air become larger outside the plane than inside it.
In airplanes, this difference in pressure creates problems for passengers and pilots. When a pilot steps on the brakes, he or she is reducing the volume of the cockpit area, which reduces the amount of space for the air inside the plane to move around. So even though there is still plenty of space for the air to move around outside the plane, within the cockpit this doesn't seem like it can be true. The only way to make more room for the air inside the plane is to reduce the pressure outside through various methods such as opening the window or deploying emergency slides.
Passengers also experience pressure differences between inside and outside the plane. While flying at high altitudes where the air is thin, passengers have less difficulty breathing than people on the ground.
There are fewer air molecules over a given surface at higher elevations than at lower heights. Because the majority of the molecules in the atmosphere are confined close to the earth's surface by gravity, air pressure declines fast at first, then more slowly at higher heights. At an altitude of 10,000 feet (3,048 m), for example, there are only about half as many particles in the air compared with sea level.
At high altitudes there is less moisture in the air and less cloud cover to reflect sunlight back into space. This means that the average temperature is lower at high elevations than at low levels. In fact, air temperatures at different levels within the atmosphere can be significantly different.
At high elevations there is also less wind speed and greater stability because there are less forces acting on the air above any given point. This means that weather patterns at high elevations are usually more predictable which allows forecasters to make better forecasts.
Finally, higher up there is less oxygen which means that people have to go higher to live.
Oceans play a major role in determining Earth's climate but their effect is mostly limited to changing the amount of water vapor in the atmosphere. Oceans act as a reservoir for water vapor which will eventually evaporate if it isn't removed by some other process. So, oceans can increase or decrease the rate at which Earth's atmosphere changes color.
Because the amount of air molecules above a surface reduces with height, so does the pressure. Gravity keeps the majority of the molecules in the atmosphere close to the earth's surface. As a result, air pressure drops quickly at initially, then more slowly at greater elevations. At an altitude of 10,000 feet (3,048 m), the air pressure is about one-tenth that at sea level.
The air pressure at any point above the surface decreases as you go higher. This means that if you were to keep climbing up a wall that was tall enough to reach from sea level all the way to the top of Earth's atmosphere, where there is no ground under your feet, the pressure would be low enough for you to need a suit or other high-pressure environment to live in.
This doesn't mean that you would die if you reached the top of this wall of earth; it's just that you would need special equipment to be able to survive there.
At the top of this wall of earth, which is called "the stratosphere" (see below), the weather is mostly calm because there are not enough windy conditions for storms to form. There may be light snow or ice depending on the season and location on Earth.
As you descend back down to the lower levels of the atmosphere, the pressure increases again until you reach sea level pressure once more.
On summit of Mount Everest, the world's highest peak, air pressure is just around one-third that of sea level.
At sea level, air pressure varies about 1 kilopascal (kPa) for each 100 meters elevation. So, if you go up in altitude, air pressure will decrease.
However, the effect of air pressure on surface objects such as people and buildings does not depend on elevation but rather on how high they are compared to the surrounding air. If you go up in elevation near tall mountains or cliffs, the air pressure will be lower than if you went up in elevation in a valley. The only exception is if you reach the top of the mountain where there is no more elevation to gain; then the pressure will be equal to that at sea level.
The change in air pressure has important effects on human physiology. For example, it causes air travel passengers to lose water and salt through their skin, and it creates discomfort for those with high blood pressure who have to climb higher elevations.
At sea level, air pressure averages about 0.5 kilopascals (kPa). This means that if you go up in elevation, air pressure will decrease.