### Present Methods and Remaining Challenges  
The World Meteorological Organization's (WMO) recommendation for optimum condition for wind observation is a 10-m reference measurement height over an open area of at least a few kilometers around the site [29]. In practice, these conditions are hardly ever met; therefore, methods have been proposed to correct for a suboptimal site environment, called exposure correction [34; 35; 36]. These methods are based on turbulence measurements, but if those are not available, information on gusts is used instead, which means that the correction can only be applied to correct the mean wind speed, not the wind gust speed. According to WMO, the representativity of the measurements, for example over a rough surface, can be improved by adjusting the measurement height [29], but it requires a higher supporting structure or a meteorological mast, which can be costly to build.  
Quite often, the structures of interest for wind gust information are higher than 10 m. Moreover, in many places, the surface is rough, for example over cities and forests, and the measured near-surface wind gusts do not necessarily represent the wind speed maxima at the height of the structures. Strong gust events may encounter a deep layer above the surface: gust fronts associated with deep convection have been observed to cover a depth of about 200 m-2 km above the surface [37]. In situ measurement techniques have limitations in measurement height, but also in areal coverage. The majority of weather stations are located over densely-populated land areas, whereas over remote locations, such as the marine Arctic, observations are made mainly at sparse coastal locations. New techniques to measure wind gusts applying research aircraft [38] and Doppler lidar [39] could fill this gap. In this paper, we discuss these recent developments and the potential new information on wind gusts they will be able provide in the future. The aforementioned aircraft and Doppler lidar measurement techniques are shown in Figure 1. The scanning cone of the Doppler lidar can cover a range of a few hundred meters above the surface, whereas research aircraft can measure over long distances within a short time interval. Both can provide new information on wind gusts that cannot be achieved by meteorological masts alone.  
Figure 1: Illustration of the measurement techniques introduced in this study: a Doppler lidar, a meteorological mast and a research aircraft. In the background, an example of a 2D wind field is shown from a Doppler lidar (green) and the sonic anemometers at 10–100 m heights of the mast (blue). The measurements have been collected at the Danish National Test Station for Large Wind Turbines in Hovsere near the western coast of Denmark. Figure reproduced with permission from [40].  
In Section 2, the definition of a gust and how it can be estimated based on statistical theory of maxima is introduced. In Section 3, a brief review of main anemometer types that are presently used for wind gust measurements is included. However, the aim here is not to carry out a thorough review of all wind measurement techniques, but to focus on measurement techniques that can provide valuable information on wind gusts. We present an overview of the remote sensing of wind applying Doppler lidars and Doppler radars in Section 4, although the latter do not represent the temporal and spatial scales relevant for short-duration wind gusts. In Section 5, we will focus on airborne measurement techniques of wind with the main focus on the derivation of wind gusts from turbulence measurements collected on board research aircraft, but we will also briefly discuss the potential of Unmanned Aircraft Systems (UASs) to measure wind gusts. In Section 6, we will review the standard reporting practices of wind gusts, and Section 7 will concentrate on the effect of environmental conditions on wind gust measurements. Finally, in Section 8, a summary is provided with an outlook to the future challenges and opportunities in wind gust monitoring.