Stretching from the Americas to Asia and washing Antarctica in the south, the Pacific, including such arms as the Philippine, Coral and Tasman Seas, which are part of it in all but name, covers about one-quarter of the globe. The equator traverses the ocean, and about half of it lies within the tropics. On such an expanse of water the influences of the sun and the spin of the earth are unimpeded. Within a band straddling the equator the heated tropical air rises, creating a sultry region of calms or light winds, shifting a few degrees north or south with the seasons. This equatorial band, the doldrums, is typically some 250 kilometres wide, and east of 160 west longitude lies permanently north of the equator (Figure 1.1). The rising equatorial air flows north and south and descends near the margins of the tropics to be drawn towards the equator again as a continually circulating ‘cell’ of air – the classical Hadley cell of climatology (Figure 1.2). The Coriolis force created by the west-to-east rotation of the earth deflects wind flow to the left in the southern hemisphere and to the right in the northern hemisphere. Thus are created the north-east and south-east trade winds. These dominate the tropical Pacific environment – winds from the east are recorded for over 80% of the time for many islands – as well as much of its romantic image. However there are periods when the trades do drop away and for days on end westerly winds dominate.