Wind gusts in the atmospheric boundary layer

• Main Author: Suomi, Irene
• Format: Thesis
• Language: English
• Published: Finnish Meteorological Institute 2017
• Subjects: wind gust; atmospheric boundary layer; wind energy; meteorological mast; parametrization; Arctic
• Online Access: http://hdl.handle.net/10138/215229

Wind gusts, which are short duration (typically 3 s) wind speed maxima, are representative of the extreme wind conditions. They are very important for human activity, because the strongest gusts associated with storms are the most significant single cause of natural hazards. The impact of wind gusts on different structures depends on the characteristics of each structure. For example for wind energy, it is important to know both the probability of extreme maximum gusts in time scales of decades for the design of power plants and in the shorter term to support wind turbine operations. For wind gust forecasting it is essential to have reliable wind gust observations. Traditionally, observations have only been available from weather stations here the wind is usually measured at a reference height of 10 m. For wind energy, information is needed at greater heights, as the hub heights of the largest turbines extend even above 150 m. The main aim of this work has been to investigate wind gusts across the entire atmospheric boundary layer based on observations from tall meteorological masts as well as applying new measurement methods developed in this dissertation. The novel methods are based on turbulence measurements taken onboard a research aircraft and by a Doppler lidar. The research aircraft can fly long distances in a short time, so the measured wind speeds do not represent wind speed variation in time but they are a function of flight distance. The new method developed in this dissertation to compare temporal and spatial scales allows the measurement of wind gusts from a research aircraft. Then, observations can be obtained from places where traditional weather stations or meteorological masts cannot be deployed. Applying the new method, the observed wind gusts from the marine Arctic matched well with those observed at a meteorological mast in the Baltic Sea, although also differences were observed between these environments. Doppler lidar provides radial wind speed measurements along a laser beam transmitted by ...