Weather Measure
Thursday, March 15, 2007
What Is a Wind Rose?
 
The wind rose is the time honored method of graphically presenting the wind conditions, direction and speed, over a period of time at a specific location. To create a wind rose, average wind direction and wind speed values are logged at a site, at short intervals, over a period of time, e.g. 1 week, 1 month, or longer. The collected wind data is then sorted by wind direction so that the percentage of time that the wind was blowing from each direction can be determined. Typically the wind direction data is sorted into twelve equal arc segments, 30° each segment, in preparation for plotting a circular graph in which the radius of each of the twelve segments represents the percentage of time that the wind blew from each of the twelve 30° direction segments. Wind speed data can be superimposed on each direction segment to indicate, for example, the average wind speed when the wind was blowing from that segment's direction and the maximum wind speed during the logging period. A good example of a wind rose application is shown at the following URL http://www.wcc.nrcs.usda.gov/climate/windrose.html. Another
site that has some interesting wind rose information and a simple program for generating a wind rose is http://www.windpower.org/en/tour/wres/rose.htm.

The information provided by the wind rose can be applied to many and varied situations. Sailors use wind rose information taken from the "Pilot Charts" by the U.S. Naval Oceanographic Office to get average winds for each ocean for each month of the year to help the create optimal sailing routes between ports. Architects do, or should, use wind rose information for the siting of buildings and stadiums. If wind rose data had been collected and used prior to the construction of San Francisco's famous windy Candlestick Park, the stadium could have been placed a few hundred yards to the north where it would have been protected from the prevailing westerly wind. Windpower "farms" do extensive wind rose type studies prior to erecting their wind turbines. Thus the wind rose is a simple information display technique that has a multitude of uses.

More wind rose links

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