Unit 1.1 Earth's Atmosphere, Solar Radiation, and Seasons Lecture HawkNet

Unit 1 Earth Systems and Resources

1-1 Introduction to Climate

• Primary Objectives:

  • Describe the composition and characteristics of the Earth’s atmosphere.

  • Understand the Greenhouse Effect.

  • Explain how the sun causes global wind patterns.

  • Explain how the sun creates various climate zones and the occurrence of seasons.

  • Describe the impact of Earth’s geography on weather and climate.

  • Understand the El Niño Southern Oscillation.

The Nature of the Atmosphere

• The atmosphere is divided into layers characterized by variations in temperature due to differences in solar energy absorption.

• Two differing factors in the layers include density and atmospheric pressure.

  • Density: Amount of molecules in a specific volume. Higher at sea level.

  • Atmospheric Pressure: Force or mass per unit area of a column of air, also higher at sea level.

Atmospheric Pressure and Temperature

• Atmospheric pressure is measured in millibars and varies with altitude:

  • Pressure decreases with increasing altitude, generally illustrated in a pressure profile.

  • Temperatures and pressure readings at various layers include:

    • Troposphere - Layer closest to the surface (75-80% of air mass).

    • Other layers: Stratosphere, Mesosphere, Thermosphere, with unique temperature profiles.

Troposphere

• Composed mainly of:

  • 78% Nitrogen (N2) and 21% Oxygen (O2).

  • Trace gases include Ozone (O3), Methane (CH4), Carbon Dioxide (CO2), and Nitrous Oxide (N2O).

  • Water vapor content varies from 0.1% to 4% depending on location (poles to equator).

• Air movements in the troposphere significantly influence weather and climate phenomena.

Greenhouse Gases and the Greenhouse Effect

• Major greenhouse gases:

  • Water Vapor, CO2, CH4, and N2O.

• Characteristics:

  • Allow visible light and some radiation to pass through and trap heat in the atmosphere.

  • Process:

    1. Solar energy penetrates atmosphere.

    2. Earth's surface absorbs and re-radiates energy as infrared radiation.

    3. Greenhouse gases absorb some of this energy, resulting in the Greenhouse Effect, vital for habitability.

• Human impact on global warming is linked to increased greenhouse gas emissions through fossil fuels and deforestation.

The Stratosphere and Ozone Layer

• Stratosphere: Ranges from 11 miles to about 30 miles above Earth.

  • Contains less density but has higher concentrations of specific gases (lower O3 and increased O2).

• Ozone Layer located between 11 and 19 miles, absorbs significant UV radiation, protecting the earth from sun-related harm such as skin cancers and immune damage.

• Ozone is formed from a reaction: 3O2 + UV = 2O3.

Weather vs. Climate

• Weather: Conditions at a specific time and place (humidity, wind speed, temperature, rainfall).

• Climate: Average weather over longer periods, influencing the distribution of living organisms.

Uneven Heating and Climate Zones

• The sun heats the earth unevenly due to:

  • Direct sunlight at the Equator versus angled sunlight at the poles.

  • Factors affecting climate zones include latitude, Earth’s tilt, and rotational position throughout the year.

• Major climate zones are:

  • Tropical, Temperate, and Polar regions.

The Convection Cells and Coriolis Effect

• Convection Cells: Hot air rises at the equator and at about 60° N & S, cools, and descends at roughly 30° N & S and at the poles.

• Coriolis Effect: Earth’s rotation causes moving air to deflect:

  • Right in the Northern Hemisphere and Left in the Southern Hemisphere, impacting wind patterns (Trade Winds).

Ocean Currents and Their Effects

• Oceans influence weather patterns assigning heat through ocean currents, moving warm surface water to poles and cold water from poles back to the equator.

• Ocean Conveyor Belt: A crucial system of deep ocean currents affecting global climate.

El Niño-Southern Oscillation (ENSO)

• In normal years, tropical easterlies push warm water towards Southeast Asia.

• During ENSO, these winds may weaken or reverse.

  • Resulting issues:

    • Decreased rainfall in Southeast Asia.

    • Increased rainfall in Americas.

    • Disruption of marine food webs due to decreased nutrients.

Local Climate Influences

• Local climates are affected by:

  • Bodies of water (moderating temperature fluctuations).

  • Topographic features (mountains create rain shadows).

  • Urban factors (Heat Islands due to concrete and pollution).

Biomes and Climate Interactions

• Biomes shaped by:

  • Greenhouse effect, convection cells, climate zones, and local geography.

• Diverse biomes encompass varied climates, soils, and ecosystems.

• Interactions between precipitation and temperature significantly affect biome distribution.