Final answer:
An Indian sailor seeking to trade in Africa should leave India during the summer months to take advantage of the favorable northeastern monsoon winds for sailing towards Africa's eastern coast.
Step-by-step explanation:
If you were an Indian sailor seeking to trade in Africa, the best time of year to leave India would be during the summer when the monsoon winds are favorable. According to historical patterns of Indian Ocean trade, these winds blow sailing ships northeast toward the coast of India, facilitating oceanic trade between the regions. The rise of the Swahili city-states on the East African coast capitalized on this seasonal trade, as the summer winds were advantageous for sailing towards India, while the winter winds would help traders return to Africa with their goods.
Commercial ships like dhows, which were prominent in this region, were particularly well-suited for this trade, equipped with lateen sails that allowed them to navigate effectively with and into the wind. Given that the monsoon winds grow weaker the farther south you go, it's important for sailors to time their voyages in accordance with these winds for the safest and most profitable journeys. These seasonal patterns were integral in fostering the trade relationships between southern Asia and East Africa, with bustling trade ports developing as a result.
Therefore, an Indian sailor targeting trade with Africa would plan to depart during the summer months when the northeastern monsoon winds would be most supportive for traveling towards Africa's eastern coast. This would allow for the most efficient utilization of the winds and contribute to the success of the expedition.