Analysis of Observational Characteristic Features of the Eulerian Autocorrelation Function in Low and Moderate Wind Conditions

Abstract

Turbulent data from three sites are utilized to analyze the characteristic features of the Eulerian autocorrelation function (EAF) of horizontal (longitudinal and lateral) wind components and temperature under different regimes of wind speed and near-surface atmospheric stability. It is shown that classical formulations do not adequately describe the observed EAF behaviour and are unable to capture the peak of the significant negative observed lobe. These formulations are modified by introducing a phase angle $\alpha$ to make them consistent with the observations. The modified formulations are shown to better characterize the behaviour of the EAF curve and its absolute value of significant negative lobe ($\left|{R}_{Min}\right|$) for both low and moderate wind conditions for all three datasets. Further, a new parametrization for the meandering parameter m is proposed in terms of the observed value of $\left|{R}_{Min}\right|$ without using any formulations for the EAF. It is found that the majority of low and moderate wind data belong to the significant meandering range, although the extent of meandering is found to be relatively more pronounced at low wind speeds as compared to moderate wind speeds. The occurrence of meandering (low-frequency horizontal wind oscillations) is found to be independent of stability, topography, and geographical location.