Monsoon: Nature and Scope

13 Março 2018, 10:00 • Shiv Kumar Singh

Throughout the last few thousand years the mariners and trade routes of the Indian Ocean have moved to a unique rhythm based upon the prevailing seasonal weather patterns. These are known individually as a monsoon, derived from the Arabic mawsim, meaning a fixed time of year. Two main monsoons can be identified: blowing from the north-east in the winter and the south-west during the summer with a variable weather season in between.

These two monsoons have very different characteristics from each other, despite occurring over the same body of water. The north-easterly monsoon of the winter is characterised by dry, steady, relatively gentle winds which encourage sailing throughout its duration. Meanwhile, the south-westerly summer monsoon is wet, violent and characterised by storms and strong wind with sailing only feasible at the beginning and end; in the late spring and early autumn. Unlike in the Mediterranean and Northern Europe, then, sailing in the Indian Ocean tended to avoid the summer months of June, July and August.

The switch in overall wind direction resulting from the monsoon patterns means that it is possible to sail on the Indian Ocean with a constantly favourable wind, if done in conjunction with the monsoon rhythms. Using favourable winds as much as possible was important. Ancient and medieval Indian Ocean sailing vessels could only sail to windward in lighter winds and calm seas, but were efficient when sailing with the wind. They could average as much as 11 kph on extended voyages, with an even higher top speed in very good conditions. The use of the monsoon in this manner is inferred in Roman period written sources. One of which is the Periplus Maris Erythraei, a Greek text written in the mid-1st century AD by a merchant with intimate knowledge of the Red Sea, Persian Gulf, Bay of Bengal and Arabian Sea. The Periplus lists the ports of trade, the distances between them and the products that could and should be traded at each port. In this sense, it is much more of a trading gazeteer than a description of navigational methods. Sometime before 100 B.C., Greek sailors coming from Egypt discovered a shortcut to India.  Much easier and more direct than the arduous overland route, or than hugging the deserted coastlines of Arabia and Persia for 5,000 miles, this route took only weeks to travel.  Sailing straight out into the open waters of the Arabian Sea during the late spring, ships were whisked by the monsoon winds on a steady northeast course, arriving on India’s west coast by mid-summer. It was a daring feat for those first sailors who attempted it.  In a time when ships rarely ventured out of sight of land, and open waters invited the prospect of drifting aimlessly at sea, it took an extraordinarily bold, unlucky, or stupid navigator to sail out into one of the largest bodies of water on the planet.  Fortunately for those first crews who made the attempt, they were saved by one of the great forces of nature: the monsoon.