1 The Atmosphere and Its Energy Free Online FlashCards

What are the two main gases in dry air near Earth’s surface?

Dry air near Earth’s surface is about 78% nitrogen and 21% oxygen, with just under 1% argon and much smaller amounts of other gases.

How does water vapor differ from the main gases in its atmospheric abundance?

Water vapor varies widely, from nearly absent in cold, dry air to several percent in warm, humid air. It also absorbs outgoing infrared energy.

Why does air become thinner with altitude?

Gravity holds the atmosphere close to Earth, making air densest near the surface and thinner with increasing altitude.

Which atmospheric layer contains nearly all weather?

The troposphere extends from the surface to about 8–15 km. It contains most atmospheric mass and nearly all weather; temperature generally decreases with height.

Why does temperature generally rise with height in the stratosphere?

In the stratosphere, ozone absorbs ultraviolet radiation, so temperature generally increases with height.

What happens to many meteors in the mesosphere?

The mesosphere extends roughly from 50 to 80 km. Temperature generally decreases with height, and many meteors burn up there.

Where in the atmosphere do auroras occur?

In the thermosphere, sparse gases absorb energetic solar radiation, and temperatures increase with height. Auroras occur in this region.

How do greenhouse gases and clouds affect outgoing infrared energy?

Earth’s warmed surface emits mainly longwave infrared radiation. Greenhouse gases and clouds absorb and emit some of it, warming the lower atmosphere and surface while some energy escapes to space.

What determines Earth’s temperature over long periods?

Over long periods, Earth’s temperature depends on the balance between absorbed solar energy and energy returned to space.

Why does the Sun heat Earth unevenly by latitude and season?

Earth’s curvature concentrates sunlight more near the equator, while sunlight reaches the poles at a lower angle. Axial tilt changes sunlight angle and duration through the seasons.

How does convection move air near a warmed surface?

Surface-warmed air expands, becomes less dense, and rises; cooler, denser air sinks and flows in to replace it. This convection transfers energy vertically.

What role does the pressure-gradient force play in wind?

Air tends to move from higher pressure toward lower pressure. This pressure-gradient force helps produce wind.