Long-live High Frequency Gravity Wavesin Atmospheric Boundary Layer: Observations and Simulations

Abstract

<p><strong>Abstract.</strong> A long-live gravity wave (GW) in atmospheric boundary layer (ABL) during a field experiment in Anqing, China (116°58′ E, 30°37′ N) is analysed. Persistent GWs over 10 hours with periods ranging from 10 to 30 min in the ABL within 2 km height are detected by a coherent Doppler lidar from 4 to 5 in September 2018. The amplitudes of the vertical wind due to these GWs are about 0.15~0.2 m s<sup>−1</sup>. The lifetime of the GWs is more than 20 wave cycles. There is no apparent phase progression with altitude. The vertical and zonal perturbations of the GWs are apparent quadrature with vertical perturbations generally leading ahead of zonal ones. Based on experiments and simplified 2-Dimensional Computational Fluid Dynamics (CFD) numerical simulations, a reasonable generation mechanism of this persistent wave is proposed. A westerly low-level jet of ~ 5 m s<sup>−1</sup> exists at the altitude of 1~2 km in the ABL. The wind shear around the low-level jet lead to the wave generation in the condition of light horizontal wind. Furthermore, a combination of thermal and Doppler ducts occurs in the ABL. Thus, the ducted wave motions are trapped in the ABL with long lifetime.</p>

Modelling the impact of trapped lee waves on offshore wind farm power output

“…Thus, it is not possible to directly compare the methodologies and deduce the optimal conditions to transfer to other studies. Recent studies (Ollier et al, 2018;Jia et al, 2019) used RANS to model TLWs, but do not detail their damping methodology. The literature discussed here uses LES configurations rather than RANS, some of which include a precursor 135 domain , unlike the current work.…”