Inversion of Temperature

Under normal conditions, temperature decreases as we go higher in the troposphere at a rate of 6.5°C per km (Normal Lapse Rate). However, there are times when the reverse happens—temperature increases with altitude instead of decreasing. This phenomenon is known as Temperature Inversion, where warm air lies above cold air, preventing vertical mixing.

Types of Temperature Inversion

1. Non-Advectional Inversion (Static Atmosphere)

These occur without horizontal air movement and are mainly caused by radiation or subsidence of air.

(a) Ground or Surface Inversion (Radiation Inversion)

• Occurs near the Earth’s surface due to radiation cooling.
• Common during long, cold winter nights in snow-covered regions of mid- and high-latitudes.
• Favorable Conditions:
  • Cloudless sky → No clouds to trap outgoing heat, allowing the surface to cool rapidly.
  • Dry air near the ground → Less water vapor means lower heat retention.
  • Slow-moving air → Prevents mixing and cooling stays confined to lower levels.

(b) Upper Air Inversion

• Thermal Upper Air Inversion: Caused by the ozone layer in the stratosphere, which absorbs UV rays, leading to an increase in temperature in this layer.
• Mechanical Upper Air Inversion: Occurs at higher altitudes due to the subsidence (sinking) of air, which compresses and warms as it descends.

2. Advectional Inversion (Caused by Air Movement)

These inversions occur due to horizontal or vertical movement of air masses and are common in cyclonic conditions, coastal areas, and mountain valleys.

(a) Frontal or Cyclonic Inversion

• Happens in temperate regions where warm westerlies meet cold polar winds (Temperate Cyclones).
• Cold air forces warm air upwards, causing inversion.

(b) Surface Inversion

• Caused when air masses of different temperatures interact with each other
• Examples:
  • Summer: Inversion over water takes place. Here is how:
    • When warm air moves into a region of cold air, it is lighter and gets pushed upward by the denser cold air.
    • Conversely, when cold air moves into a warm region, it slides underneath the warm air, lifting it up and creating an inversion layer.
  • Winter: Inversion on land takes place

(c) Valley Inversion

• Common in mountain valleys, where cold air sinks and remains trapped.
• Caused by radiation cooling and lack of vertical air movement(after inversion occurs).

Significance of Temperature Inversion

While inversion plays a critical role in weather patterns, it has both positive and negative effects.

1. Fog and Smog Formation

• Fog: When warm air is cooled by the inversion layer, water vapor condenses into fog.
• Smog: In urban areas, fog mixes with smoke from industries, creating smog, which is hazardous for health.
  • Example: London’s “Great Smog” of 1952.

2. Impact on Agriculture

• Frost Formation: If the warm air cools below freezing point, frost develops, which is harmful to crops. In this context, always remember following concept:
  • Above freezing point → Water droplets (dew) form.
  • Below freezing point → Water vapor converts to frost, damaging crops like potatoes, tomatoes, and peas.
• Beneficial Effects:
  • In Yemen Hills, fog protects coffee plants from direct sunlight.

3. Effect on Fishing Industry

• Coastal fog attracts plankton, making regions like the Peruvian Coast rich in fish.

4. Atmospheric Stability and Dry Conditions

• Prevents rainfall by restricting air movement (stable conditions).
• Encourages dry climates, making rainfall, cyclones, and thunderstorms less likely.

Conclusion

Temperature inversion disrupts normal atmospheric behavior, affecting weather, agriculture, pollution, and climate stability. While it can create stable, dry conditions, it also leads to smog, frost damage, and reduced rainfall—profoundly influencing human activities and ecosystems. 🌍❄️☁️