Question: what does the movement of air masses cause

title: Trade winds
text: The term trade winds originally derives from the early fourteenth century late Middle English word ' trade , ' meaning `` path '' or `` track . '' The Portuguese recognized the importance of the trade winds ( then the Volta do mar , meaning in Portuguese `` turn of the sea '' but also `` return from the sea '' ) in navigation in both the north and south Atlantic ocean as early as the 15th century . From West Africa , the Portuguese had to sail away from continental Africa , that is , to west and northwest . They could then turn northeast , to the area around the Azores islands , and finally east to mainland Europe . They also learned that to reach South Africa , they needed to go far out in the ocean , head for Brazil , and around 30 ° S go east again . Following the African coast southbound means upwind in the Southern hemisphere . In the Pacific ocean , the full wind circulation , which included both the trade wind easterlies and higher - latitude Westerlies , was unknown to Europeans until Andres de Urdaneta 's voyage in 1565 .