Question

In gradient wind balance, which of the following statement(s) is/are true for flow around a region of low pressure in the northern hemisphere?

• A. The flow is clockwise.
• B. The flow is anti-clockwise.
• C. The wind speed is faster than the geostrophic wind.
• D. The wind speed is slower than the geostrophic wind.

Hint:

In the Northern Hemisphere, winds around low-pressure systems rotate counterclockwise (anti-clockwise), and the wind speed is often slower than the geostrophic wind due to the centripetal forces involved.

Answer 1

The Correct Option is B, D

In the gradient wind balance, the wind speed and direction are influenced by both the Coriolis force and the centripetal force. For low-pressure regions, the wind is subject to different forces compared to high-pressure regions. - Option (A) The flow is clockwise:
This is incorrect. In the Northern Hemisphere, the flow around low-pressure systems is counterclockwise due to the Coriolis effect. The winds are deflected to the right, resulting in counterclockwise rotation around low-pressure systems.
- Option (B) The flow is anti-clockwise:
This is correct. In the Northern Hemisphere, the flow around low-pressure systems is anti-clockwise due to the Coriolis effect. This is a fundamental characteristic of cyclonic flow in the Northern Hemisphere.
- Option (C) The wind speed is faster than the geostrophic wind:
This is incorrect. In gradient wind balance, the wind speed around a low-pressure system can be faster than the geostrophic wind when centrifugal forces are considered, but it does not necessarily always exceed the geostrophic wind. The gradient wind balances centripetal and Coriolis forces, and the wind speed can vary.
- Option (D) The wind speed is slower than the geostrophic wind:
This is correct. For low-pressure systems, the wind is often slower than the geostrophic wind because of the additional effect of centripetal acceleration, which causes the wind to be less than the geostrophic wind in some cases. This is a key difference between gradient wind balance and pure geostrophic balance.
Thus, (B) and (D) are correct answers.