geol 150 week 8 lecture 1

Overview of El Niño

• El Niño is a complex climate phenomenon with opposing effects depending on the region.

  • Effects vary from droughts to floods, influencing different areas uniquely.

Regional Impacts of El Niño

• West Pacific:

  • Experiences dry conditions leading to events like forest fires in Indonesia, impacting air quality.

• California and South America:

  • Typically sees increased rainfall during El Niño.

Historical Context of the Name 'El Niño'

• Named for its association with the Christmas season, reflecting historical observations of changes in Peruvian fisheries.

  • Local understanding connected it with supernatural forces and the birth of Jesus, as missionaries noted the phenomena.

• El Niño events are aperiodic (non-periodic), occurring every 2-7 years, complicating prediction.

Temperature Anomalies and Atmospheric Effects

• Temperature Variances:

  • Areas like the Eastern Equatorial Pacific can experience warming of 3-4 degrees Celsius.

  • La Niña events typically cooler by 2 degrees with their own regional impacts.

• Precipitation Changes:

  • Rainfall patterns shift dramatically; sometimes creating excess rainfall while adjacent areas may experience drought.

ENSO: El Niño Southern Oscillation

• El Niño is part of the larger ENSO cycle, which includes:

  • El Niño (warm phase).

  • La Niña (cold phase).

• Interaction between sea surface temperature and atmospheric conditions plays a critical role in predictions.

Ocean and Atmosphere Interactions

• Normal Conditions:

  • Hadley circulation causes air to rise near the equator, affecting ocean currents and temperatures.

• El Niño Development:

  • Weakening of trade winds allows warm water to shift eastward, altering weather patterns and feedback loops.

• Trade winds adjustment can enhance or reduce atmospheric conditions, leading to either El Niño or La Niña phases.

Measuring and Understanding El Niño

• Indices:

  • Measurement of sea level pressure and sea surface temperatures (especially the Niño 3 index) helps in tracking and predicting El Niño events.

• El Niño impacts can be seen in temperature, pressure changes, and their transformations in the atmosphere leading to global weather patterns.

Health and Economic Implications

• El Niño significantly impacts agriculture, fisheries, and health:

  • Altered rainfall leads to food shortages, vector habitats for diseases, and impacts on various economies.

• Close relationships between weather changes and financial markets, affecting everything from food supplies to stock trading.

Climate Feedback Mechanisms

• Positive Feedback Cycle:

  • Changes in land use and vegetation affect soil moisture retention, exacerbating drought conditions during El Niño events.

• Excessive dry periods lead to dust storms, creating respiratory health issues (dust pneumonia).

Historical Examples of Impact

• The Dust Bowl (1930s) exemplified how poor land management and climate can intersect:

  • Agriculture practices that removed native grasses made soil vulnerable to erosion and desertification.

• Lessons learned from this period highlighted the importance of sustainable land management practices.

Prediction and Its Importance

• Modern prediction of El Niño events can occur up to two years in advance:

  • Methods involve studying warm water volumes in the western Pacific and linking these to global weather changes.

  • Successful predictions help guide agricultural planning globally, ensuring farmers can adapt to expected conditions.

  • The ability to forecast El Niño events has been a significant success in climate science, improving resilience in affected regions.