### History of Wind Gust Measurement Techniques
The interpretation of such measurements was not trivial, and still, in 1941, [PERSON] commented that the class of acoustic anemometers is \"of no practical importance\" [16]. However, already at the end of the 1940s, the first instrument to measure temperature based on the propagation velocity of the sound was developed [24], and in 1955, Schotland presented the theory to measure wind velocity by sonic means [25]. [PERSON] and [PERSON] (1963) developed a sonic anemometer that was able to measure both wind and temperature and thereby the eddy heat flux using a vertically-aligned acoustic array [26]. They used two different frequencies for transmission of signals in the two directions. The use of two-way signals canceled the side-wind effect on the wind measurement that was an inevitable disadvantage of one-way signals [25]. This type of approach is still used in modern sonic anemometers [27], where sound pulses are used instead of continuous waves. When the travel times of two-way sound pulses are measured between three different transducer pairs, called sonic paths, the three-dimensional wind vector can be derived. The direct measurement of the three wind velocity components with a system allowing a high frequency of measurements (up to 100 Hz or even more) revolutionized the atmospheric boundary layer research [18], as for the first time, it was possible to directly measure the turbulent fluxes of momentum and buoyancy using eddy covariance technique. Because of these features, sonic anemometers can also be considered as reference instruments for wind gusts. In the early days of anemometry, the main challenge was to obtain uniform and comparable information on wind force on ships, because suitable recording techniques did not exist. To overcome this problem, Admiral Sir [PERSON] created his well-known scales for wind and weather measurements. The Beaufort scales were first mentioned in a private log in 1806, but the scales were only adopted for wider use much later: the first U.K. Board of Trade publication, the Barometer Manual, mentioned them in 1862 [28]. The Beaufort scales for wind consist of 12 different classes, which are based on qualitative assessment of conditions the wind is causing on the environment at sea. The scales were later converted to units of wind speed [29]. The scales were actively used on ships for over a hundred year period, until the 1980s, providing thus the longest observational time series of winds [30]. Towards the end of the 20 th Century, recording practices and signal processing developed. At weather stations from the 1950s onwards, wind gusts were recorded on anemographs from which they were manually read [31]. The first automatic meteorological observing systems were introduced in the 1980s in order to provide observations from remote locations such as Antarctica [32]. At the end of 1980s, the advances in Radio Frequency (RF) communications and microprocessor technology made it possible to establish automatic networks for mesoscale measurement systems, including tens of weather stations measuring wind and other in situ meteorological parameters [33]. Automatization allowed also the calculation of gust speeds using running means [31]. Today, wind gust observations are no longer limited by data processing, recording or reporting techniques because of powerful computers, efficient means of RF communications and inexpensive data storage resources. Moreover, anemometers have reached such a high accuracy that the limited representativeness of point observations is nowadays a larger problem than the anemometer inaccuracy [29; 31].