In-Depth Notes on Atmospheric Science II

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Announcements

  • Midterm exam date: Saturday, January 25, 9-11 am at UTM.
    • Details about room assignments will be posted.
    • No aids allowed during the exam.
    • Arrive by 9 am.

El Niño, La Niña, and the Southern Oscillation

  • Concepts Covered:
    • El Niño, La Niña, and the Southern Oscillation (ENSO)
    • Their global/local effects on weather and wildlife.

What is ENSO?

  • Definition: ENSO = El Niño-Southern Oscillation
    • Represents temperature and air pressure anomalies in the equatorial Pacific.
    • Characterized by periodic fluctuations in sea surface temperatures and atmospheric pressure.
    • Influences global weather patterns and climate.
    • Climate change impacts ENSO behavior.
ENSO Cycle Effects
  • Weather/Climate Impact:
    • Alters precipitation, temperature, and atmospheric circulation.
    • Influences hurricanes, monsoons, and droughts.
    • Important for agriculture, water management, and disaster preparedness.

Origin of Terms

  • El Niño: From Spanish meaning "the little boy".
    • Observed mainly around Christmas by 19th-century Peruvian fishers due to warming coastal waters and reduced fish catches.
  • La Niña: Spanish for "the little girl", indicating the cooling phase observed subsequently.

ENSO Cycle Phases

  • The ENSO cycle consists of three phases:
    1. El Niño
    2. La Niña
    3. Neutral
    • Irregular timing and intensity, not strictly sequential.

Measuring ENSO: Southern Oscillation Index (SOI)

  • Definition: A standardized index measuring sea level pressure differences between Tahiti and Darwin.
  • Negative SOI: Indicates below-normal air pressure at Tahiti (El Niño) and above-normal at Darwin.
  • Correlates strongly with sea surface temperatures (SST).

Effects on Jet Streams

  • El Niño:
    • Weakens the polar jet stream.
    • Less temperature gradient leads to meandering, which affects storm tracks (e.g., drier conditions in Southern Ontario).
  • La Niña:
    • Strengthens the polar jet stream.
    • Increases precipitation in northern Canada; often associated with heavy snowfall in BC and dryer conditions in the Southern US.

Summary on ENSO

  • El Niño and La Niña are manifestations of SST and air pressure anomalies in the equatorial Pacific.
  • They are part of a larger system that connects tropical and extratropical regions, impacting global weather patterns and local ecosystems.

Atmospheric Pollutants and Aerosols

  • Topics Covered:
    • Ambient air pollution contributions.
    • Aerosols' influence on the climate system.

Composition of Air

  • Major components include:
    • Nitrogen (N₂): 78.08%
    • Oxygen (O₂): 20.95%
    • Other gases: Argon, Neon, Helium, Hydrogen (trace)
    • Most variable: Water vapor (0-4%) and aerosols (varied sources).

Understanding Air Pollution

  • Definition: Air pollutants are gases or particulates that can be harmful.
    • Natural or anthropogenic origins.
  • Importance of distinction:
    • Pollutant: A substance harmful to health.
    • Contaminant: A foreign substance that may or may not be harmful.

Types of Air Pollutants

  • Primary Pollutants: Directly harmful (e.g., carbon monoxide).
  • Secondary Pollutants: Form from reactions of primary pollutants (e.g., ozone).

Smog and Its Types

  • Industrial Smog:
    • “Grey air” from SO₂ and particulates, associated with coal burning.
  • Photochemical Smog:
    • “Brown air” from NOx and VOCs; aggravated by sunlight and common in urban areas.

Impact on Health

  • PM < 2.5 µm has serious health risks, especially for vulnerable populations (elderly, infants).

Aerosols

  • Definition: Tiny particles or droplets suspended in air, can be solid or liquid.
  • Influence cloud formation and climate.
  • Classification by size: referred to as PM2.5 or PM10.
  • Natural vs. anthropogenic sources:
    • Natural: sea spray, dust storms, wildfires, volcanic eruptions.
    • Anthropogenic: industrial emissions, transportation, agriculture, waste burning.

Acidic Deposition

  • Associated with primary pollutants (sulfur dioxide, nitrogen oxides) leading to acid rain.
  • Harms ecosystems by causing nutrient leaching, harming aquatic life and vegetation.

Conclusion on Air Pollution

  • Air pollution includes gases and particulates that affect health and ecosystems negatively.
  • The sources are both natural and human-made, and both contribute to ecological and health challenges.
    • Priority air criteria contaminants require regulation (SO₂, NO₂, PM, VOCs, CO, NH₃, and O₃).