Periods of constant wind speed: how long do they last in the turbulent atmospheric boundary layer?

We perform a statistical analysis of the occurrence of periods of constant wind speed in atmospheric
turbulence. We hypothesize that such periods of constant wind speed are related to characteristic wind field
structures that, when interacting with a wind turbine, may induce particular dynamical responses. Therefore,
this study focuses on characterizing the constant wind speed periods in terms of their lengths and probability
of occurrence. Atmospheric offshore wind data are analyzed. Our findings reveal that long constant wind speed
periods are an intrinsic feature of the marine atmospheric boundary layer (ABL). We confirm that the probability
distribution of such periods of constant wind speeds follows a Pareto-like distribution, admitting power law
behavior for periods exceeding the large-eddy-turnover time. The power law characteristics depend on the local
conditions and the precise definition of wind speed thresholds. A comparison to wind time series generated
with standard synthetic wind models and to time series from ideal stationary turbulence suggests that these
structures are not characteristics of small-scale turbulence but seem to be consequences of larger-scale structures
of the atmospheric boundary layer and thus are multi-scale. Given the results, we show that the continuous-time
random walk (CTRW) model, as a non-standard wind model, can be adapted to generate time series of the wind
speed whose statistics match the statistics of observed periods of constant wind speed.