Different people have very different reasons for becoming familiar with concepts pertaining to the average daily wind speed, due to its relevance to so many human activities. Enthusiasts of sports that rely on the wind-- such as kitesurfers -- may need to know about average daily wind speeds when planning an outing or selecting a vacation destination. On a larger scale, the average daily wind speed is used to determine placement of wind turbines for power generation, and to determine flight paths in the aviation industry.
Wind is caused by the natural tendency of air to flow from areas of high pressure to areas of low pressure. Generally, average wind speed increases with increasing altitude. Winds are slowest at ground level, and fastest at the level of the jet stream. Certain factors can influence the average daily wind speed at a particular ground-level location, including obstructions such as buildings or trees and proximity to hills or large bodies of water.
Measuring and Calculating
Wind speed for a particular locale is typically measured using an anemometer. To assess wind speeds at higher altitudes, meteorologists deploy weather balloons. At official National Weather Service and Federal Aviation Administration sites in the U.S., averages are calculated every two minutes, and compiled over a 24-hour period to produce the daily average. Depending on the intended audience -- for instance, scientists, pilots or the general public -- the average daily wind speed may be reported in knots, kilometers per hour, or miles per hour. Daily wind speed measurements cannot assess, however, the frequency at which very high winds occur.
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In the U.S., daily wind speeds typically average between 6 and 12 miles per hour (10 and 19 kilometers per hour) throughout the course of a year. These averages vary widely by geographic location. For instance, of major cities, Boston is the windiest, with an average wind speed of 12.3 miles per hour (19.8 kilometers per hour), while Phoenix is the calmest, clocking in at 6.2 miles per hour (10 kilometers per hour), an average about half that of Boston’s.
Geographic and Seasonal Variation
Although there are other factors, a location’s latitude can give a hint as to whether its average daily wind speeds will be high or low. Worldwide, the area near the equator is notoriously calm, known colloquially as “the doldrums.” The nonequatorial tropics experience strong breezes known as the trade winds, but around 30 degrees latitude, there is often a deficit of wind. Many people assume that daily average wind speeds are highest during the early springtime in most North American locales, but this is not always the case. For instance, Buffalo, N.Y., experiences its highest average daily wind speed in January, while San Francisco is windiest in June.