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In Canada, reference wind pressures are used in design and are based on the "mean hourly" wind speed having a probability of being exceeded per year of 1 in 50. The reference wind pressure q is calculated using the equation q = ρv 2 / 2 , where ρ is the air density and v is the wind speed.
Wind speed on the Beaufort scale is based on the empirical relationship: [6] v = 0.836 B 3/2 m/s; v = 1.625 B 3/2 knots (=) where v is the equivalent wind speed at 10 metres above the sea surface and B is Beaufort scale number.
A short burst of high speed wind is termed a wind gust; one technical definition of a wind gust is: the maxima that exceed the lowest wind speed measured during a ten-minute time interval by 10 knots (19 km/h; 12 mph) for periods of seconds. A squall is an increase of the wind speed above a certain threshold, which lasts for a minute or more.
In common usage, wind gradient, more specifically wind speed gradient [1] or wind velocity gradient, [2] or alternatively shear wind, [3] is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. [4] It is the rate of increase of wind strength with unit increase in height above ground level.
A wind rose is a graphic tool used by meteorologists to give a succinct view of how wind speed and direction are typically distributed at a particular location. Presented in a polar coordinate grid, the wind rose shows the frequency of winds blowing from particular directions.
A wind gust or just gust is a brief, sudden increase in the wind speed. It usually lasts for less than 20 seconds, briefer than a squall, which lasts minutes. A gust is followed by a lull (or slackening) in the wind speed. [1] Generally, winds are least gusty over large water surfaces and most gusty over rough land and near high buildings. [2]
Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height ...
The definition of sustained winds recommended by the World Meteorological Organization (WMO) and used by most weather agencies is that of a 10-minute average at a height of 10 m (33 ft) above the sea surface. However, the Saffir–Simpson hurricane scale is based on wind speed measurements averaged over a 1-minute period, at 10 m (33 ft).