鄭和航海與季風問題－前聞記的啟示

古代帆船交通靠季風，《前聞記》記載了宣德年鄭和出航的人數、日期、停靠港口、船號等。由此我們不但可估算各段海域航行速度，而且了解到船隻過洋時，是如何選擇航道去順應季風的方向。本文討論重點：(1)船隊在福州候風開洋，是遵循「北風去南風回」的航海古律。(2)船隊進出印尼泗水，也是依據赤道風場東風入西風出的季節規律，然而他們停留該處128天之久，原因有待探究。(3)從蘇門答剌亞齊開往錫蘭，常因季節過早，船隊必須從亞齊北駛到邊翠蘭山(Great Nicobar)或更北海域，等候東北風渡海。(4)古里開往忽魯謨斯時，正逢冬季逆風，船隊選擇沿著印度海岸北行至丁得把昔(Tundavoli)後，才斜渡阿拉伯海進入阿曼灣，是為縮短洋面航行距離以免迷航危險。(5)回程駛到長江口前，適值江西瀕江八府大水江漲，船隊被迫停靠碗碟嶼5天，等待洪鋒消退，以策安全。下西洋之旅，航速最快者估計應為沙姑馬往古里這段海程，依據「順風相送」的記載，這段海程每天可行265公里(折11km/hr)，此乃因冬季風方向與航向相同。這個航速與徐玉虎估計的8.3-12.5km/hr接近，但比李露曄估計的14.4km/hr慢很多。

關鍵字

鄭和航海；丁得把昔；前聞記；季風氣候

並列摘要

Zheng He's last voyage (1431AD-1433AD) was recorded in the book of Qian-Wen-Ji which depicted numbers of crew, types of ships, dates of arrival and departure at each port of call. These records help us to calculate the sailing speeds of the ships on the seas and, in some cases, the departure dates could indicate the beginning of a monsoon season. There are five issues for discussion: (1) The ships obeyed the monsoonal rhythm at Fuzhou for both out-bound and back-bound sails. (2) Zheng He's fleet anchoring 128 days at Surabaya was a mystery and should be explored. (3) When the ships departed early in winter season from Aceh to Sri Lanka, they had to reach to a higher latitude- i.e., Great Nicobar to catch up to the NE wind. (4) When sailing against wind from Calicut to Hormuz in winter, the fleet took a safety measure first to sail along the Indian coast to Tundavoli Bay before heading for Ras Al Hadd in a NW direction to pick up the better side-wind in the Arabian Sea. (5) Before returning to Yang Tzu River, the fleet encountered a huge flood and had to station on the Bow-Dish Islands for 5 days. The highest sailing speed was estimated to be 265 kilometers per day when returning from Ras Al Hadd to Calicut based on the record of Shun Feng Xiang Song. In this case, the ships were riding with a suitable tail-wind in late winter.