Very-large scale motions in the atmospheric surface layer

Abstract

Very-large scale motions (VLSMs) are typical structures in wall-bounded turbulence at high Reynolds number, which make important contributions to mass and energy transport. This talk will present the atmospheric surface layer observations carried out at the Qingtu Lake observation array (QLOA) site. Furthermore, some studies on the VLSMs in the atmospheric surface layer based on the observed data are introduced, including the morphological and dynamic characteristics of the VLSMs and its effect on the sand dust transportation. The influences of dust particles and heat flux on the VLSMs are discussed as well. It is found that the length scale of the VLSMs has Reynolds number invariance, and evidenced that the VLSMs in the atmospheric surface layer evolute with a top-down mechanism. In the sand-laden flow, the energy of the VLSMs increases, while their energy fraction decreases. The inclination angle of the VLSMs increases with the increase of dust concentration. It is revealed that the VLSMs dominates the streamwise transport of PM10 (tiny particles with size less than 10 μm), but suppress the vertical transport of PM10 near the surface. Finally, it is demonstrated that the temperature and PM10 in the atmospheric surface layer have large structural feature similar as the VLSMs, though the shape of temperature and PM10 structures are different with the VLSMs.