Strong winds pose a very real risk to people and material. The potential of damage depends not only on the maximum wind speed, but also on the duration and thus the transported energy of the wind. Due to this (and because of measurement system differences), meteorologists measure the size of the gust instead of the maximum speed peak.
Image Credit: Khamkéo Vilaysing via Unsplash
In this article, OTT Hydromet outline what a gust of wind can do, how it is defined and how to reliably measure gusts and without any extra accessories with the Lufft Ventus and Lufft V200A.
Haiyan, Katrina, Kyrill, Nargis – years after storms these storms occurred, the names still evoke images of the serious damage which impacted the affected areas for decades. Hurricanes can cause mass destruction and claim thousands of lives. The terms typhoon, hurricane or cyclone are only local, regional terms.
In addition to air pressure and diameter, a key parameter that meteorologists use to describe hurricanes is wind speed. The aforementioned storms all made headlines with speeds exceeding 200 kilometers per hour, and Typhoon Haiyan hit a peak speed of 315 km an hour. the table below offers an overview of the storms, their dimensions and their effects.
Storms, their dimensions and effects. Source: Wikipedia
Different Measuring Methods
Accurately measuring wind speeds is a science in its own right. The speed data is relative to the values averaged over one minute. Accordingly, the winds achieve even higher speeds at their peak. However, for a number of reasons, it makes little sense to show the maximum value versus the strongest gust of wind.
On the one hand, extremely short wind peaks transfer little energy and thus have low damage potential. However, the longer the wind blows, the greater the energy transfer to anything standing in its way. On the other hand, various measuring methods act in response to a gust of wind with varying strengths or at different speeds.
For example, due to their mechanical resistance, analog cup anemometers (anemometers are wind gauges) require a precise start-up time. Thus, they react more inertly and do not have the capacity to detect very short gusts of wind in detail.
Ultrasonic sensors have the ability to detect short gusts while functioning without moving parts, i.e., they have no bearings that could suffer damage. However, in cold regions, they require sufficient electricity for the built-in heating system to keep themselves free of icing.
In essence, anemometers are categorized according to four main measuring principles:
- Dynamic pressure anemometers
- Mechanical anemometers (cup anemometer, impeller anemometer)
- Thermal anemometers
- Ultrasonic anemometers
Wind Gusts: An Important Measurement Parameter
Besides strong hurricanes, meteorologists also use wind gusts as a measurement parameter. Rather than averaging the wind speed over a full minute or even ten minutes, they take into account shorter wind pulses of 3 to 20 seconds.
Hence, the measuring instruments should continually display the average value of all values recorded in the previous 3 to 20 seconds. Consequently, meteorologists acquire values that are, firstly, more comprehensive than a very short gust of wind and, secondly, facilitate a better comparison of the various measuring methods.
The following illustration highlights the difference between the maximum measured value and the Gust value averaged over 3 seconds, i.e., the strength of the wind gust.
The difference between the maximum measured value and the Gust value averaged over 3 seconds. Image Credit: OTT HydroMet
There are a variety of specifications used to define a wind gust in technical terms. A commonly shared recommendation by weather services and the World Meteorological Organization WMO states:
- Indication of the highest 3-second value per measuring interval of 10 minutes.
(In the illustration (interval over 70 seconds), the device would consequently output 1.7 as the greatest value, measured at around 55 seconds.)
- Moving average over the previous 3 seconds
Implementation of Wind Gust Measurement in Ventus and V200A
To facilitate simple and reliable wind gust measurements, OTT Hydromet has updated its ultrasonic anemometers Lufft Ventus and Lufft V200A. Without the need for an extra logger or computer, the devices with the firmware update version 33 now have the capacity to output the wind gust values in addition to all known data.
OTT Hydromet’s sensors Ventus and V200A can calculate the gust value from all measured values of the previous 3 seconds and provide an update with a frequency of 4 Hertz, i.e., every 250 milliseconds. The highest Gust value per 10-minute interval can then be communicated.
For additional information, check out the respective product pages for the Lufft ultrasonic anemometers Ventus and V200A, as well as the Ventus X for use in extremely cold conditions.
This information has been sourced, reviewed and adapted from materials provided by OTT HydroMet. Lufft is one of OTT HydroMet's strong brands for professional environmental monitoring.
For more information on this source, please visit OTT HydroMet.