When the Coriolis effect is counter balanced by the pressure gradient force, the resulting wind is termed as:

The correct answer is option 3.

Key Points

• Geostrophic winds occur when the pressure gradient force (which moves air from high to low pressure) is exactly balanced by the Coriolis force (due to Earth's rotation). Hence, option 3 is correct.
• This balance causes the wind to flow parallel to the isobars (lines of constant pressure) rather than directly from high to low pressure.
• Geostrophic winds are typically found in the upper atmosphere where friction is negligible.

Additional Information

• Polar Winds:
  • Definition: Cold, dry winds that blow from the polar high-pressure areas towards lower latitudes.
  • Origin: These winds originate in the polar regions and flow towards the sub-polar low-pressure zones.
  • Characteristics:
    • Generally cold and dense.
    • Flow from high to low pressure but are deflected by Coriolis force, contributing to the polar easterlies.
  • Not a result of balanced Coriolis and pressure gradient forces, but influenced by them.
• Prevailing Winds:
  • Definition: Winds that blow predominantly from a particular direction over a region.
  • Example:
    • Westerlies in mid-latitudes,
    • Trade winds in the tropics.
  • Characteristics:
    • Result of general atmospheric circulation and pressure patterns.
    • Include both geostrophic and ageostrophic components.
  • Not specifically the balance of Coriolis and pressure gradient forces but influenced by them.