A&O TA Review

Atmospheric Circulation

• Simplified Circulation Models

  • Two primary circulation cells without Coriolis effect: one in Northern Hemisphere, one in Southern Hemisphere.

  • Coriolis effect results in three circulation patterns in each hemisphere.

• Types of Circulation Cells

  • Hadley Cells: Closest to Equator.

  • Mid-Latitude Cells: Found in middle latitudes.

  • Polar Cells: Located near the poles.

• Direction of Circulation

  • Upper branches of Hadley and Polar cells flow towards the poles.

  • Mid-Latitude cells rotate in the opposite direction.

• Jet Streams

  • Located between circulation cells, with two main jet streams:

    • Subtropical Jet Stream: Between Hadley and Mid-Latitude cells, influenced by the Coriolis effect.

    • Polar Jet Stream: Between Polar and Mid-Latitude cells, caused by temperature differences at air boundaries.

  • No jet stream at the Equator due to minimal temperature difference and negligible Coriolis effect.

Effects of Tropical Circulation

• Tropical circulation leads to:

  • Warm air rising at the equator, causing cloud formation and high precipitation.

  • Sinking cool air around 30° North and South latitudes, leading to arid conditions.

• Impact on Ocean Salinity

  • Precipitation at the equator reduces ocean salinity; high salinity found at mid-latitudes.

Density and Stratification in Ocean

• Density Drivers

  • Influenced by temperature and salinity:

    • Higher temperatures = Lower density.

    • Higher salinity = Higher density.

  • Density increases with depth due to these factors.

• Stratification

  • Warmer, fresher water sits at the surface due to lower density, forming layers.

  • Stratification: Stable vertical layering; hard to mix surface waters with deep waters.

• Mixing Factors

  • Evaporation: Increases salinity by reducing water volume.

  • Precipitation: Decreases salinity by adding fresh water.

Ocean Conveyor Belt and Climate Change

• Ocean conveyor belt circulation driven by thermal and haline processes is vital for global climate.

• Changes in Arctic regions due to climate change threaten vertical mixing and circulation.

• Surface winds also influence ocean currents but less significantly than the ocean conveyor belt.

Land Biosphere Interactions

• Photosynthesis and Respiration

  • Photosynthesis requires sunlight and occurs mainly during the day.

  • Respiration occurs day and night, contributing more CO2 back to the atmosphere.

Climate Change and Carbon Emissions

• Sources of CO2 Emissions:

  • Major contributors include burning fossil fuels (coal, oil, gas, and cement).

  • 41.6 gigatons of CO2 emitted from human activities annually.

• Carbon Uptake by Oceans

  • Involves solubility and biological pumps, affecting global carbon cycles.

Radiation and Greenhouse Effect

• Solar Radiation: Different wavelengths emitted by the sun and Earth.

  • Shortwave radiation from the sun vs. longwave radiation from Earth.

  • Greenhouse gases trap longwave radiation, contributing to global warming.

• Temperature Increase

  • Land temperatures rising faster than ocean temperatures, with significant implications for climate patterns.

Feedback Mechanisms in Climate Change

• Water Vapor Feedback: Increased evaporation leads to more greenhouse gas emissions.

• Surface Albedo Feedback: Melting ice reduces albedo, leading to further warming.

• Cloud Feedback: Changes in cloud cover can either cool or warm the atmosphere, creating complex interactions.

Historical Climate Patterns

• Cycles of cold and warm periods, such as Pleistocene and Holocene, can inform current climate scenarios.

Predictions and Climate Models

• Climate Sensitivity: Indicates temperature response to doubled CO2 concentrations.

• Adaptation of models to incorporate AI and computational methods for improved predictions.

• Radiative Forcing: Unbalanced energy at the top of the atmosphere creates a new equilibrium state, influencing global climate patterns.

• Intergovernmental Agreements

  • Paris Agreement aims to limit global temperature rise, with actions needed to achieve substantial reductions in emissions.