## 8 Conclusions and Outlook  
The aims of this work were as follows: (1) to give an overview of traditional wind gust measurement techniques applied in meteorology and some historical insight to their development; (2) to present recent developments to measure wind gusts based on Doppler lidar and research aircraft data; and (3) to discuss the effects of environmental conditions on measuring wind gusts. Wind gusts are measured operationally at weather stations all over the world. The measurements are taken applying mainly cup and sonic anemometers, which in ideal conditions are placed at a 10-m reference height. The practices related to the measurements and international data exchange are coordinated by WMO, who recommends measuring the wind gust speed as a 3-s maximum of wind speed during a 10-min sampling period [29]. However, in practice, there are regional differences both in sampling and reporting practices. Gusts may be reported only when a certain threshold value is exceeded or only during the 10-min period prior to the hourly observation time. Then, the resulting wind gust time series have gaps that may cause errors in estimating return periods for extreme wind loads necessary for structural design and, for example, in the insurance field. Moreover, the overall accuracy of the measurements includes not only the accuracy of the anemometer system, but also the environmental conditions. The changes in the environmental conditions surrounding the weather station may cause artificial changes in the measured wind gust climate. The weather station measurements have many limitations. The environmental conditions may be suboptimal due to shadowing effects of obstacles nearby the anemometer. Sometimes, a better representativeness of the observations is obtained by increasing the measurement height, but even then, the measurements are point-wise, and no information is available on the horizontal and vertical variability of wind gusts. Moreover, the weather stations are typically located in places were they are easy to apply. The majority of stations are located over densely-populated land areas, whereas in remote locations such as the marine Arctic, only a few stations exist, and those are mainly located at sparse coastal locations. Figure 10: Mean gust factor profiles over (**a**) smooth grassland and (**b**) rough forest surface. In (**a**), the dashed lines are based on sonic anemometer data from a meteorological mast, and the solid lines are from the corresponding data from a Doppler lidar. The theoretical curve in (**b**) is based on Equation (24) with the height \(z\) replaced by \(z-d\), where \(d=11\) m is the displacement height. The roughness length is \(z_{0}=2.5\) m. Gust factors are normalized by the value at the lowest level. Error bars show the standard error of the mean. Stability groups are defined as \(\text{vu}/\text{u}\): unstable (\(-200<L<-50\)), \(\text{nu}/\text{n}/\text{n}\text{s}\): near neutral \(|L|>\)200 and \(\text{vs}/\text{s}\): stable (\(10<L<200\)). Redrawn with permission from [40]. New measurement techniques based on remote sensing and airborne measurements can provide valuable information on wind gusts complementing that based on the existing weather station network. Exploitation of these measurements will be a challenge in the forthcoming years. Doppler lidars can provide valuable information on wind gust profiles. Such information could be used, for example, to find out the optimal measurement height and location for the traditional anemometer at a weather station. Doppler lidars could also be utilized to investigate the formation and the origin of wind gust events, which could further be used to develop parameterizations for NWP and climate models to forecast wind gusts. Existing parameterizations can be divided into surface-based methods and a profile method. Surface-based methods aim at estimating the gust factor, which is the ratio of the wind gust speed to the mean wind speed. It depends on the height above the surface, surface roughness and the static stability of the atmosphere.