Question

What will happen to the speed of a balanced flow as one moves across the isobar along a particular latitude?

• A. The speed changes for a geostrophic flow and remains constant for a cyclostrophic flow
• B. The speed remains constant for a geostrophic flow and changes for a cyclostrophic flow
• C. The speed remains constant for both (geostrophic and cyclostrophic) types of flow
• D. The speed changes for both (geostrophic and cyclostrophic) types of flow

Hint:

Key memory: Geostrophic flow = stable constant speed along isobars; Cyclostrophic flow = variable speed due to curvature effects.

Answer 1

The Correct Option is B

Step 1: Recall geostrophic balance.
- Geostrophic flow occurs when pressure gradient force (PGF) is balanced by the Coriolis force. - The geostrophic wind speed depends on the pressure gradient and latitude, but across an isobar (same pressure gradient), the speed remains constant.
Step 2: Recall cyclostrophic balance.
- Cyclostrophic flow occurs when PGF is balanced by centrifugal force (important in small-scale circulations like tornadoes). - In this case, the speed varies with radius and curvature → hence it changes when moving across the isobar.
Step 3: Eliminate incorrect options.
- (A) Incorrect → geostrophic flow speed does not change across an isobar. - (C) Incorrect → cyclostrophic flow speed changes. - (D) Incorrect → not both, only cyclostrophic flow speed changes. Final Answer: \[ \boxed{\text{(B) The speed remains constant for a geostrophic flow and changes for a cyclostrophic flow}} \]