19.1 Power outline earth space science
19.1 P.O. Air Pressure and Wind
P.1:1. Swirling in complex patterns, air moves constantly across Earth’s surface. Wind, which is the horizontal movement of air, helps to moderate surface temperatures, distribute moisture, and generally cleanse the atmosphere. 2. Although several forces affect the direction in which the air moves, differences in air pressure are what set the air in motion.
A. What is Air Pressure? P.2:1. “light as air” is a common expression, but a column of air that stretches from the top of the atmosphere to sea level has, in fact, considerable weight, equivalent to 14.7 pounds per square inch. 2. The weight of the atmosphere as it pushes down upon Earth’s surface exerts a force per unit of area called air pressure.
P.3:1. Air pressure is exerted in all directions because air molecules move in all directions. If you hold your hand out, palm up, the force of air pushing down on your hand is greater than your own weight. 2. Yet you do not feel the air pushing down because there is also air under your hand, pushing up, and there are forces inside your body pushing out. 3. All of these forces are in balance. So critical is the balance of these forces to the human body that astronauts in space must work in pressurized cabins or wear pressurized suits that re-create air pressure similar to that experienced on Earth.
P.4:1. Because air pressure at any point on Earth’s surface depends on the weight of the air above, air pressure decreases as elevation increases. In general, air pressure decreases by about 50% for each 5-km increase in elevation. 2. Mile High Stadium in Denver, Colorado, is about 1.6 km above sea level. The air exerts a pressure about 82% of that experienced at sea level (an 18% decrease). A jet aircraft flying over Denver at an altitude of 10km moves through air that exerts a pressure only 25% of that experienced at sea level.
P.5:1. Air pressure is probably most noticeable when you experience a change in
P.1:1. Swirling in complex patterns, air moves constantly across Earth’s surface. Wind, which is the horizontal movement of air, helps to moderate surface temperatures, distribute moisture, and generally cleanse the atmosphere. 2. Although several forces affect the direction in which the air moves, differences in air pressure are what set the air in motion.
A. What is Air Pressure? P.2:1. “light as air” is a common expression, but a column of air that stretches from the top of the atmosphere to sea level has, in fact, considerable weight, equivalent to 14.7 pounds per square inch. 2. The weight of the atmosphere as it pushes down upon Earth’s surface exerts a force per unit of area called air pressure.
P.3:1. Air pressure is exerted in all directions because air molecules move in all directions. If you hold your hand out, palm up, the force of air pushing down on your hand is greater than your own weight. 2. Yet you do not feel the air pushing down because there is also air under your hand, pushing up, and there are forces inside your body pushing out. 3. All of these forces are in balance. So critical is the balance of these forces to the human body that astronauts in space must work in pressurized cabins or wear pressurized suits that re-create air pressure similar to that experienced on Earth.
P.4:1. Because air pressure at any point on Earth’s surface depends on the weight of the air above, air pressure decreases as elevation increases. In general, air pressure decreases by about 50% for each 5-km increase in elevation. 2. Mile High Stadium in Denver, Colorado, is about 1.6 km above sea level. The air exerts a pressure about 82% of that experienced at sea level (an 18% decrease). A jet aircraft flying over Denver at an altitude of 10km moves through air that exerts a pressure only 25% of that experienced at sea level.
P.5:1. Air pressure is probably most noticeable when you experience a change in