Why do the trade winds of the Southern Hemisphere become the southwest monsoon after crossing the Equator?

Correct answer: Due to the Coriolis force they turn right

The direct answer is A: due to the Coriolis force, the winds turn to the right after crossing the Equator. Trade winds in the Southern Hemisphere generally blow toward the northwest as they move toward the equatorial low-pressure belt. After crossing into the Northern Hemisphere, Earth’s rotation deflects moving air to its right. Their direction therefore becomes generally southwesterly, producing the southwest monsoon flow toward India. Option A is correct because it identifies the force responsible for this directional deflection. Option B is wrong because the Himalayas can block and redirect air in the region, but they do not explain the initial rightward turning after Equator crossing. Option C is wrong because the Western Ghats affect rainfall and local wind movement, not this broad hemispheric deflection. Option D is wrong because El Niño can influence monsoon strength, but it is not the reason for the rightward Coriolis turn. Exam cue: crossing into the Northern Hemisphere means deflection to the right.