Multi-scale entropy analysis of single-point wind speed in outdoor near-surface environments

Odor/gas dispersion in atmospheric boundary layer is mainly controlled by airflow. The analysis of the wind speed/direction properties is helpful for understanding the odor/gas dispersion mechanism. Twenty groups of wind speed/direction time series are measured using an ultrasonic anemometer. Multi-scale entropies of wind-speed series in along-wind and across-wind directions are analyzed. The results indicate that the entropy of wind speed in outdoor near-surface environments is larger than zero, and the entropy increases with an increase in scales. In general, high mean wind speed corresponds to large entropy, which is more obviously reflected in across-wind direction. The further analysis indicates that the entropy decreases with an increase in the kurtosis of wind speed under different scales. This shows that the stronger intermittency of wind speed results in the more regular wind-speed series.