Rossby Waves and Wet Bulb Temperature

News: A recent study links warming oceans with rising humid heatwaves, highlighting atmospheric processes like Rossby waves influencing large-scale heat extremes.

About Rossby Waves

• Rossby waves are large horizontal atmospheric undulations that move westward and influence global weather and climate patterns.
• Mechanism
  • Role of coriolis effect: The Rossby waves form due to the variation of the Coriolis effect with latitude, which affects moving air and water.
  • Deflection of moving air: When air moves toward the poles, it gets deflected and then curves back to conserve its potential vorticity.
  • Formation of wave pattern: This repeated deflection creates a large oscillating wave pattern that propagates westward.
  • Heat transfer function: These waves help in transferring heat between the tropics and the poles, maintaining earth’s energy balance.
• Key types and characteristics
  • Atmospheric rossby waves
    • Nature and occurrence: These appear as large undulations in the jet stream and influence weather patterns over wide regions.
    • Ridges and troughs: They create ridges, which bring warm, dry, and high-pressure conditions and troughs, which bring cold, wet, and low-pressure systems such as cyclones.
  • Oceanic rossby waves
    • • Movement and location: These move slowly across ocean basins along the thermocline, which lies between warm surface water and colder deep water.
      • Impact on deep water: Although surface changes are small, they cause significant shifts in deeper water layers over long time periods.
    • Topographic rossby waves
      • • Formation: These are formed when physical barriers like mountains or ocean ridges disturb the normal flow of air or water.
        • Effect of physical features: Such disturbances force the flow to adjust its path, leading to the development of wave patterns.

About Wet Bulb Temperature

• Wet bulb temperature is the lowest temperature that can be reached by air through evaporation of water under given conditions.
• Basis: It is the temperature of air cooled to saturation (100% humidity) by evaporation, with heat supplied by the air parcel itself.
• Human impact and threshold: Wet-bulb temperatures above about 31°C–31.5°C can prevent the human body from cooling through sweating and increase mortality risk.
• Measurement: It is measured using a thermometer covered with a wet cloth, where evaporation cools the reading below dry temperature.