How to read a Wind Rose

The wind rose is used to provide a synthetic overview of wind speed and wind direction frequency distribution at a given location.

Wind speed can be estimated with several scales. One of the first was created by Britain's Admiral Sir Francis Beaufort (1805). The Beaufort scale is an empirical scale that relates wind speed to observed conditions at sea or on land. The original scale goes from 0 to 12, but the Clima Tool will show the results from 1 to 9 since it is not common to construct buildings in places with recurrent winds over 100 km/h.

Graphical illustration of the Beaufort scale. The colors shown for each scale value are those used in the tool's charts. Source: howtoons

Each circle segment shows the winds according to the cardinal direction along which they blow from.

Geographical coordinates in the wind rose

The length of each radius around the circle shows how often the wind blew from that direction. A click of the mouse over each slice of the rose shows therefore the recurrence frequency in which the wind of such intensity is repeated over the analyzed period.

Frequency of wind intensity recurrence in the wind rose

As most graphs in Clima Tool, the wind rose is strongly interactive. Clicking on the legend will hide or highlight the selected category. As such, it is easy to go from a wind rose showing all the wind directions and frequency to one that highlights only the selected speed range. This can be particularly useful to identify low-frequency, high-speed wind patterns.

Left: wind rose showing all velocity ranges Right: the same data can be easily filtered (by clicking on the legend) to show only direction and frequency of wind speeds above 10.7m/s

In the seasonal graphs section, Clima shows 4 wind roses for the periods of:

• December - February;

• March - May;

• June - August;

• September - December.

Personal viewing periods are available using the last portion of the Wind section, where a wind rose of the desired interval can be generated.

In building design, the wind is addressed in several forms:

• assessing pedestrian and outdoor comfort;

• design for wind-driven natural ventilation;

• understanding pollution dispersal and outdoor air quality;

• in warm climates, thoughtful design of indoor patios or wind towers can provide naturally mitigated environments;

• in renewable energy, wind data are used to design wind turbines;

• in structural analysis, wind load considerably influences the design of roofs, sheds, or overhanging elements.