Question

In the figures given below, L and H indicate low and high pressure centers, respectively; PGF, CoF and CeF indicate Pressure Gradient Force, Coriolis Force and Centrifugal Force, respectively; V is Velocity. [The arrows indicate only the directions but not the magnitudes of the forces and velocity.]

Which of the following is/are the correct representation(s) of the directions of various forces and velocity in the gradient wind balance in the northern hemisphere?

• A. (i)
• B. (ii)
• C. (iii)
• D. (iv)

Hint:

In the Northern Hemisphere: cyclones rotate counter-clockwise with inward PGF; anticyclones rotate clockwise with outward PGF. Gradient wind balance always involves PGF, Coriolis, and centrifugal forces.

Answer 1

The Correct Option is A, C

Step 1: Recall gradient wind balance.
In the northern hemisphere, around curved flow: - For a low-pressure system (cyclone), the velocity is anticlockwise. Forces balance as: \[ \text{Pressure Gradient Force (PGF) inward} = \text{Coriolis (to right of flow) + Centrifugal (outward)}. \] - For a high-pressure system (anticyclone), the velocity is clockwise. Forces balance as: \[ \text{Pressure Gradient Force (PGF) outward} = \text{Coriolis (to right of flow inward) + Centrifugal (inward)}. \]

Step 2: Analyze figure (i).
Low pressure center (L). PGF points inward toward the center. Centrifugal force outward. Coriolis to the right of velocity. This is correct for cyclonic gradient wind.

Step 3: Analyze figure (ii).
High pressure (H). But here the balance shown is inconsistent (PGF direction mismatched).

Step 4: Analyze figure (iii).
High pressure (H). PGF outward, centrifugal outward, Coriolis inward balancing them. This is correct for anticyclonic gradient wind in the Northern Hemisphere.



Step 5: Analyze figure (iv).
Low pressure (L), but the force alignment is incorrect (Coriolis drawn opposite to expected). Final Answer:
\[ \boxed{\text{(i) and (iii) are correct.}} \]