Sci quiz march 1

1. The Atmosphere: Composition & Structure

• Most Abundant Gases:

  • Nitrogen (N₂): Approximately 78%.

  • Oxygen (O₂): Approximately 21%.

  • (The remaining 1% is made of argon, CO₂, and other trace gases.)

• Troposphere Temperature: In this layer (where we live), temperature decreases as altitude increases. Think of it this way: the further you get from Earth's surface (which absorbs solar heat), the colder it gets.

• Atmospheric Layers (Bottom to Top):

  • Troposphere: Closest to Earth; contains all weather and 80% of the atmosphere's mass.

  • Stratosphere: Contains the Ozone Layer (which absorbs UV radiation); temperature actually increases here.

  • Mesosphere: The coldest layer; this is where meteors burn up.

  • Thermosphere: The outermost layer; contains the Ionosphere and is where the International Space Station orbits.

2. Energy and Heat

• The Ultimate Source: The Sun is the primary source of energy that drives all weather on Earth.

• Specific Heat (Heat Capacity): This is the measure of how much energy is needed to change the temperature of a substance.

  • Water has a high specific heat (it heats up and cools down slowly).

  • Land has a low specific heat (it heats up and cools down quickly).

• Weather Impact: This difference is why coastal areas usually have more moderate temperatures than inland areas.

3. Local Winds: Land & Sea Breezes

Winds are caused by convection currents created by differences in air density and pressure.

• Sea Breeze (Daytime):

  1. Land heats up faster than water.

  2. Warm air over land rises (Low Pressure).

  3. Cooler, denser air from the sea moves in to fill the gap.

• Land Breeze (Nighttime):

  1. Land cools down faster than water.

  2. Air over the water is now warmer and rises (Low Pressure).

  3. Cooler air from the land moves out toward the sea.

4. Air Pressure & Global Winds

• How Air Pressure Works: It is the weight of the atmosphere pressing down on us.

  • Altitude: Pressure decreases as you go higher (fewer air molecules).

  • Temperature: Warm air is less dense and rises (creating Low Pressure); cold air is denser and sinks (creating High Pressure).

• Wind Formation: Wind is simply air moving from areas of High Pressure to Low Pressure.

• Coriolis Effect: Because the Earth rotates, winds don't blow in a straight line. They appear to curve (to the right in the Northern Hemisphere and to the left in the Southern Hemisphere).

• Global Wind Belts:

  • Trade Winds: Blow from east to west near the equator.

  • Prevailing Westerlies: Blow from west to east in the mid-latitudes (this is what moves most weather across the US).

  • Polar Easterlies: Cold winds blowing away from the poles.

5. High vs. Low Pressure Centers