chapter 1

Chapter 1: Earth and Its Atmosphere MEA 130

Introduction

  • The atmosphere is critical for life on Earth, impacting weather, climate, and the overall functionality of ecosystems.

Objectives

  • Discuss why the atmosphere is important.

  • List the relevant gases that compose the atmosphere, including greenhouse gases.

  • Become familiar with the vertical structure of the atmosphere, including:

    • Variations in pressure and temperature with altitude.

    • Different layers of the atmosphere.

  • Distinguish between weather and climate.

  • Identify various tools used to analyze weather.

  • Learn about the impacts of weather and what meteorologists do.

The Importance of the Atmosphere

  • Acts as a medium for sound and odors, allowing us to hear and smell.

  • Contains 8 km of breathable air crucial for human existence.

  • Holds water vapor, playing a significant role in the water cycle and preventing water from escaping into space.

  • Regulates Earth's temperature and protects from harmful radiation, showcasing a stark contrast between Earth and other celestial bodies (e.g., Mercury).

Earth's Position in Space

  • Earth is approximately 150 million km away from the Sun.

  • It intercepts only a small fraction of the Sun’s total energy output (solar radiation).

  • Average surface temperature of Earth is 15°C (59°F):

    • Minimum recorded temperature: -89.2°C (-128.6°F) at Vostok Station, Antarctica.

    • Maximum recorded temperature: 56.7°C (134.1°F) in Death Valley, California, USA.

The Atmosphere as a Thin Blanket

  • Atmosphere extends for hundreds of miles, but 99% is located within 30 km (19 mi) of the surface.

  • If scaled down to the size of a beach ball, the habitable part of the atmosphere would be as thin as a sheet of paper.

  • The atmosphere does not have a definitive upper limit—it gradually thins until it merges with outer space.

Composition of the Atmosphere

Permanent Gases

  • Nitrogen (N2): 78.08%

  • Oxygen (O2): 20.95%

  • Argon (Ar): 0.93%

  • Neon (Ne): 0.0018%

  • Helium (He): 0.0005%

Variable Gases

  • Water vapor (H2O): 0-4% (invisible, varies)

  • Carbon dioxide (CO2): 0.041% (410-422 ppm)

  • Methane (CH4): 0.00018%

  • Nitrous oxide (N2O): 0.00003% (0.3 ppm)

  • Ozone (O3): 0.000004% (0.04 ppm)

  • Xenon (Xe): 0.000009%

  • Chlorofluorocarbons (CFCs): 0.00000001% (0.0001 ppm)

Greenhouse Gases

  • Gases that trap heat energy close to the Earth's surface:

    • Water vapor

    • Carbon dioxide

    • Methane

    • Nitrous oxide

    • Chlorofluorocarbons

Carbon Dioxide (CO2)

  • Composition:

    • 0.0422% by volume (422 ppm)

  • Sources:

    • Exhalation by living beings

    • Decay of vegetation

    • Volcanic eruptions

  • Sinks:

    • Photosynthesis by plants

    • Dissolving into oceans

  • Anthropogenic Sources:

    • Burning fossil fuels

    • Deforestation

  • The Keeling Curve illustrates the rise in CO2 due to fossil fuels, seasonal changes in absorption, with peaks in winter and troughs in summer.

Methane (CH4)

  • More potent as a GHG than CO2 by a factor of 28.

  • Concentrations rising at approximately 0.5% per year due to:

    • Natural gas operations

    • Breakdown of bacteria in rice paddies

    • Cattle digestion

Nitrous Oxide (N2O)

  • Rises at a rate of 0.3% per year.

  • Resulting from industrial processes as well as natural formation in soil.

Chlorofluorocarbons (CFCs)

  • Concentrations peaked until the mid-1990s due to use in aerosols and refrigeration.

  • Known to destroy ozone.

Ozone (O3)

  • Functions differently at various atmospheric levels:

    • Lower atmosphere, a component of smog.

    • Higher atmosphere (stratospheric ozone) provides protection against UV radiation.

Vertical Structure of the Atmosphere

Density

  • Air molecules are suspended by gravity, compressing them close together; density decreases with altitude.

    • Air density at surface: approximately 1 kg/m³.

    • Density of water: 1000 kg/m³.

Pressure

  • Atmospheric pressure is defined as the force exerted by air molecules per unit area; varies with altitude.

  • Average pressure at sea level: 1013 mb (millibars) = 15 psi.

    • Record high: 1084 mb in Siberia (1968).

    • Record low: 870 mb during Typhoon Tip (1979).

  • Atmospheric pressure decreases with height; at ~5.5 km, half of the atmosphere's mass is below.

Atmospheric Layers

  • Troposphere: Contains all weather; temperature decreases with height; average lapse rate is 6.5°C/km; houses 80% of the atmosphere.

    • Tropopause: Constant temperature with height, varies seasonally (higher in summer, lower in winter).

  • Stratosphere: Temperature increases with height due to ozone absorption of UV radiation; contains the stratopause at ~50 km AGL.

  • Mesosphere: Low density; temperature decreases with height; high levels of UV radiation.

  • Thermosphere: Oxygen absorbs solar radiation, leading to high temperatures; contains few air molecules; responsible for auroras.

  • Exosphere: Height of 500-10,000 km; contains outermost particles and serves as an escape point for atoms and molecules into space.

Weather vs. Climate

Weather

  • Defined as the conditions of the atmosphere at a specific time and place.

  • Elements include:

    • Air temperature

    • Air pressure

    • Humidity

    • Clouds

    • Precipitation

    • Wind

    • Visibility

Climate

  • Encompasses long-term weather patterns over extensive periods (tens of years to millions of years).

  • Considers:

    • Mean and variability of meteorological variables.

    • Frequency and intensity of extreme weather events.

    • Example: average high temperatures in a region compared to daily weather conditions.

Observing Weather

  • Tools used include radiosondes, satellites, and weather maps.

  • Radiosondes (weather balloons) are launched twice daily to track temperature, moisture, wind, and pressure profiles.

  • Remote sensing through satellites provides data on visible, infrared, and water vapor imagery.

Weather Impacts

  • Significant weather and climate disasters can result in substantial economic damage:

    • In 2024, there were 27 disasters exceeding $1 billion each in damages, totaling $182.7 billion.

    • Since 1980, damages from such disasters have surpassed $2.915 trillion.

The Role of Meteorologists

Meteorologists engage in various functions, including:

  • Broadcasting: Reporting weather to the public.

  • Forecasting: Predicting future weather patterns for various sectors (e.g., aviation, military).

  • Research: Investigating weather phenomena to improve predictive models and understanding.

  • Consulting and Forensics: Providing weather data for agriculture, event planning, and legal disputes.

Chapter Overview

  • Discussion of the atmosphere's importance, composition, and structure.

  • Exploration of weather versus climate and the tools used to analyze and forecast weather, along with the impacts of weather events and the role of meteorologists in society.