As altitude/height rises, air pressure drops. In other words, if the indicated altitude is high, the air pressure is low.

This happens for two reasons. The first reason is gravity. Earth’s gravity pulls air as close to the surface as possible.

All matter, whether fluid (liquid & gas) of solid, is attracted to the Earth’s center of gravity. The pressure increase with depth in water may be more obvious to your senses, since you will feel the effect of the increase in pressure with depth simply by diving to a depth of a few meters. You can feel things happening in your ears and sinuses, and if you are wearing goggles, you can feel them being pressed into your face. The second reason is density. As altitude increases, the amount of gas molecules in the air decreases—the air becomes less dense than air nearer to sea level. This is what meteorologists and mountaineers mean by “thin air.” Thin air exerts less pressure than air at a lower altitude.

The second reason is density. As altitude increases, the amount of gas molecules in the air decreases—the air becomes less dense than air nearer to sea level. This is what meteorologists and mountaineers mean by “thin air.” Thin air exerts less pressure than air at a lower altitude.

<b style=”font-family: inherit; font-size: inherit;”>High-altitude locations are usually much colder than areas closer to sea level. This is due to the low air pressure. Air expands as it rises, and the fewer gas molecules—including nitrogen, oxygen, and carbon dioxide—have fewer chances to bump into each other.

The human body reacts to high altitudes. Decreased air pressure means that less oxygen is available for breathing. One normal effect of altitude is shortness of breath, since the lungs have to work harder to deliver oxygen to the bloodstream. It can take days and even weeks for a body to adjust to high altitude and low air pressure.