wind rose

A star-shaped diagram in which the relative frequencies of the different wind directions measured at a weather station or observatory over a given period of time are represented. The frequencies of different speed ranges grouped by direction can also be represented. The percentage corresponding to calms is noted in a circle drawn at the center of the rose. Long before wind began to be measured with instruments, the first wind roses with the bearings of the main winds were established, intended mainly to help sailors orient themselves at sea. Ancient wind roses appear in different cultures, gaining in sophistication over time. In classical times, the Greek poet Homer (8th century BC) refers in The Odyssey to a rose of four main winds (Boreas, Eurus, Notus, and Zephyrus), arranged according to the four cardinal points. The philosopher Aristotle (4th century BC) established a rose of 8 bearings, Timosthenes (3rd century BC) one of 12, and the Roman architect Vitruvius (1st century BC) one of 24. The 32-point rose used today was first depicted on a medieval world map attributed to the Majorcan geographer and cartographer Abraham Cresques (14th century), although some sources attribute its invention to the also Majorcan Ramon Llull (c. 1232-1315 or 1316). The aforementioned 32-point wind rose includes 8 main winds (four marking the cardinal points and another four being the lateral winds), 8 half winds (collateral), and 16 quarter winds (quartas).