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The Tower of the Winds in the agora in Hellenistic Athens once bore on its roof a weather vane in the form of a bronze Triton holding a rod in his outstretched hand, rotating as the wind changed direction. Below this a frieze depicted the eight Greek wind deities. The eight-metre-high structure also featured sundials, and a water clock inside ...
Wind tees and tetrahedrons can swing freely and align themselves with the wind direction, but neither provides an indication wind speed, unlike a windsock. Since a wind tee or tetrahedron can also be manually set to align with the runway in use, a pilot should also look at the wind sock for wind information, if one is available.
Wind direction is usually expressed in terms of the direction from which it originates. For example, a northerly wind blows from the north to the south. [8] Weather vanes pivot to indicate the direction of the wind. [9] At airports, windsocks indicate wind direction, and can also be used to estimate wind speed by the angle of hang. [10]
The Santa Anas are katabatic winds (Greek for "flowing downhill") arising in higher altitudes and blowing down towards sea level. [7] The National Weather Service defines Santa Ana winds as "a weather condition [in southern California] in which strong, hot, dust-bearing winds descend to the Pacific Coast around Los Angeles from inland desert regions".
Consequently, a wind blowing from the north has a wind direction referred to as 0° (360°); a wind blowing from the east has a wind direction referred to as 90°, etc. Weather forecasts typically give the direction of the wind along with its speed, for example a "northerly wind at 15 km/h" is a wind blowing from the north at a speed of 15 km/h ...
The construction of a windcatcher depends on the direction of airflow at that specific location: if the wind tends to blow from only one side, it is built with only one downwind opening. This is the style most commonly seen in Meybod , 50 kilometers from Yazd: the windcatchers are short and have a single opening.
A wind speed gradient of 4 (m/s)/km can produce refraction equal to a typical temperature lapse rate of 7.5 °C/km. [51] Higher values of wind gradient will refract sound downward toward the surface in the downwind direction, [52] eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind.
Along with wind direction, cloud cover is one of the oldest atmospheric conditions to be coded on a station model. [ 7 ] [ 8 ] The circle in the middle of the station model represents cloud cover. In the United Kingdom , when the observation is taken from an automated weather observation site, the shape is a triangle. [ 10 ]