The correct option is 40°E and 60°E.
Explanation
The Indian Summer Monsoon is significantly influenced by the cross-equatorial flow of winds. This phenomenon involves the movement of trade winds from the Southern Hemisphere into the Northern Hemisphere, driven by pressure differences between the Mascarene High and the thermal low over the Indian subcontinent.
Detailed Analysis
- Origin of Winds: The Southeast Trade Winds originate from the high-pressure area located southeast of Madagascar (Mascarene High) in the Southern Hemisphere.
- Crossing the Equator: These winds move towards the equator and cross it primarily between the longitudes of 40°E and 60°E. This region corresponds roughly to the area off the coast of East Africa (near Somalia and Kenya).
- Deflection and Transformation: As per Ferrel’s Law, once these winds cross the equator into the Northern Hemisphere, the Coriolis force deflects them to the right. Consequently, the Southeast Trade Winds transform into the Southwest Monsoon winds.
- Somali Jet: This cross-equatorial flow is often associated with the Somali Jet (or Findlater Jet), a low-level jet stream that intensifies the monsoon winds reaching the Indian subcontinent.
Key Takeaway: The Southeast Trade Winds cross the equator between 40°E and 60°E longitudes and are deflected rightwards by the Coriolis force to become the Southwest Monsoon.