🌦️Atmospheric Science Unit 1 – Intro to Earth's Atmosphere

What's the Atmosphere?

• Gaseous envelope surrounding the Earth held in place by gravity
• Protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night
• Consists of various gases including nitrogen (~78%), oxygen (~21%), and trace gases such as argon, carbon dioxide, and water vapor
• Extends from the Earth's surface to the exosphere, gradually thinning with increasing altitude
• Plays a crucial role in the water cycle by transporting water vapor and enabling precipitation
• Influences weather patterns and climate through atmospheric circulation and heat transfer
• Provides the air we breathe and is essential for the survival of most living organisms on Earth

Layers of the Atmosphere

• Troposphere: Lowest layer, contains ~75% of the atmosphere's mass, where most weather phenomena occur (clouds, precipitation)
  • Height varies from ~8 km at the poles to ~16 km at the equator due to temperature differences
  • Temperature decreases with altitude at a rate of ~6.5°C/km (lapse rate)
• Stratosphere: Layer above the troposphere, contains the ozone layer which absorbs harmful UV radiation
  • Extends from the tropopause (~8-16 km) to the stratopause (~50 km)
  • Temperature increases with altitude due to ozone absorption of UV radiation
• Mesosphere: Layer above the stratosphere, where meteors burn up and the coldest temperatures in the atmosphere occur
  • Extends from the stratopause to the mesopause (~85 km)
  • Temperature decreases with altitude, reaching as low as -90°C at the mesopause
• Thermosphere: Layer above the mesosphere, where auroras occur and the International Space Station orbits
  • Extends from the mesopause to the thermopause (~500-1,000 km)
  • Temperature increases with altitude due to absorption of high-energy radiation by oxygen and nitrogen molecules
• Exosphere: Uppermost layer, transitioning into the vacuum of outer space
  • Extends from the thermopause with no definite upper boundary
  • Extremely low density, with particles occasionally escaping Earth's gravitational pull

Atmospheric Composition

• Dry air composition: ~78% nitrogen (N2), ~21% oxygen (O2), ~0.9% argon (Ar), and trace amounts of other gases
• Water vapor (H2O) is a variable component, typically ranging from 0.1-4% depending on location and weather conditions
  • Plays a crucial role in the greenhouse effect and heat transfer within the atmosphere
• Carbon dioxide (CO2) is a trace gas (~0.04%) but has a significant impact on the Earth's climate due to its greenhouse properties
  • Concentrations have increased by ~48% since the pre-industrial era due to human activities (fossil fuel combustion, deforestation)
• Ozone (O3) is a trace gas found primarily in the stratosphere, forming the ozone layer
  • Absorbs harmful ultraviolet (UV) radiation from the sun, protecting life on Earth
• Other trace gases include methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs)
  • These gases contribute to the greenhouse effect and can have adverse environmental impacts (ozone depletion, air pollution)

Energy and Heat Transfer

• Solar radiation is the primary source of energy for the Earth's atmosphere and surface
  • Shortwave radiation (visible light and UV) is absorbed, reflected, or transmitted by the atmosphere and surface
• Earth emits longwave radiation (infrared) back into the atmosphere, which is partially absorbed by greenhouse gases and re-emitted in all directions
  • This process, known as the greenhouse effect, warms the Earth's surface and lower atmosphere
• Conduction is the transfer of heat through direct contact between substances (air and Earth's surface)
  • Plays a minor role in atmospheric heat transfer due to the low thermal conductivity of air
• Convection is the vertical transport of heat through the movement of fluids (air or water)
  • Drives atmospheric circulation patterns and the formation of clouds and precipitation
• Latent heat is the energy released or absorbed during phase changes of water (evaporation, condensation)
  • Plays a significant role in heat transfer within the atmosphere and the formation of weather phenomena (thunderstorms, hurricanes)
• Albedo is the fraction of solar radiation reflected by a surface (clouds, ice, land)
  • Surfaces with high albedo (snow, ice) reflect more radiation, while low albedo surfaces (oceans, forests) absorb more radiation

Weather Basics

• Weather refers to the day-to-day state of the atmosphere, including temperature, humidity, precipitation, wind, and cloudiness
• Atmospheric pressure is the force exerted by the weight of the atmosphere on a given surface area
  • Measured using a barometer and expressed in units such as millibars (mb) or inches of mercury (inHg)
  • High-pressure systems are associated with stable, fair weather, while low-pressure systems often bring unstable, stormy weather
• Wind is the horizontal movement of air from areas of high pressure to areas of low pressure
  • Influenced by the Coriolis effect, which deflects wind to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
• Humidity is the amount of water vapor present in the air
  • Relative humidity is the ratio of the actual water vapor content to the maximum possible water vapor content at a given temperature, expressed as a percentage
• Precipitation occurs when water vapor condenses and falls from the atmosphere in the form of rain, snow, sleet, or hail
  • Requires the presence of condensation nuclei (dust particles, ice crystals) and sufficient moisture and cooling in the atmosphere
• Clouds form when water vapor condenses around condensation nuclei in the atmosphere
  • Classified based on their shape, altitude, and composition (cumulus, stratus, cirrus)

Climate vs. Weather

• Climate refers to the long-term average weather conditions in a given area, typically over a period of 30 years or more
  • Characterized by factors such as average temperature, precipitation patterns, and seasonal variability
• Weather, on the other hand, refers to the short-term, day-to-day state of the atmosphere
  • Can change rapidly and is influenced by factors such as air pressure, humidity, and wind
• Climate is determined by a variety of factors, including latitude, altitude, ocean currents, and atmospheric circulation patterns
  • Proximity to water bodies (oceans, lakes) can moderate climate by reducing temperature extremes
• Climate zones are regions with distinct climatic conditions, such as tropical, temperate, and polar zones
  • Further classified into subcategories based on temperature and precipitation patterns (rainforest, desert, tundra)
• Climate change refers to long-term shifts in global or regional climate patterns, often attributed to human activities (greenhouse gas emissions, land use changes)
  • Can have significant impacts on ecosystems, agriculture, water resources, and human health
• Understanding the difference between weather and climate is crucial for making informed decisions related to agriculture, water management, and infrastructure planning

Atmospheric Phenomena

• Jet streams are narrow, fast-moving air currents in the upper troposphere that can influence weather patterns and air travel
  • Polar jet streams form between cold polar air and warmer mid-latitude air, while subtropical jet streams form between mid-latitude and tropical air masses
• El Niño and La Niña are periodic fluctuations in ocean temperatures and atmospheric circulation patterns in the Pacific Ocean
  • El Niño is characterized by warmer ocean temperatures and weaker trade winds, often leading to increased rainfall in the eastern Pacific and drier conditions in the western Pacific
  • La Niña is characterized by cooler ocean temperatures and stronger trade winds, often resulting in the opposite effects of El Niño
• Monsoons are seasonal wind patterns that bring heavy rainfall to certain regions, particularly in Asia and Africa
  • Caused by differential heating between land and ocean surfaces, leading to the reversal of wind direction and the transport of moisture-laden air
• Tornadoes are violently rotating columns of air that extend from a thunderstorm to the ground
  • Most common in the United States, particularly in the region known as "Tornado Alley" (Texas, Oklahoma, Kansas, Nebraska)
• Hurricanes, also known as tropical cyclones or typhoons, are large, rotating storm systems that form over warm ocean waters
  • Characterized by strong winds, heavy rainfall, and storm surges, and can cause significant damage to coastal areas
• Atmospheric rivers are long, narrow regions in the atmosphere that transport large amounts of water vapor from the tropics to higher latitudes
  • Can bring heavy rainfall and flooding to the regions they affect, particularly on the west coast of North America

Environmental Impacts and Challenges

• Air pollution refers to the presence of harmful substances in the atmosphere, such as particulate matter, ozone, and nitrogen oxides
  • Can have adverse effects on human health (respiratory issues, cardiovascular disease) and the environment (acid rain, reduced visibility)
  • Sources include transportation, industrial activities, and the burning of fossil fuels
• Acid rain is precipitation with a low pH (high acidity) caused by the reaction of air pollutants (sulfur dioxide, nitrogen oxides) with water in the atmosphere
  • Can harm aquatic ecosystems, damage forests, and corrode infrastructure
• Ozone depletion refers to the reduction of ozone in the stratosphere, primarily due to the release of ozone-depleting substances (chlorofluorocarbons, halons)
  • Increases the amount of harmful UV radiation reaching the Earth's surface, which can cause skin cancer, cataracts, and immune system suppression
• Climate change, driven by the increase in greenhouse gas concentrations, poses significant challenges for the environment and human society
  • Impacts include rising sea levels, more frequent and intense extreme weather events (heatwaves, droughts, floods), and shifts in the distribution of plant and animal species
• Mitigation strategies for addressing environmental challenges include reducing greenhouse gas emissions, promoting renewable energy, and implementing policies to improve air and water quality
  • Adaptation measures, such as building resilient infrastructure and developing drought-resistant crops, can help communities cope with the impacts of climate change
• International cooperation and agreements, such as the Paris Agreement, aim to address global environmental challenges by setting targets for reducing emissions and promoting sustainable development practices