Energy Mechanism of Atmospheric Boundary Layer Development Over the Tibetan Plateau

Abstract

AbstractThe distinct thermodynamic characteristics of the atmospheric boundary layer (ABL) over the Tibetan Plateau (TP) significantly affect regional and global climate. It is well recognized that the ABL depth over the western TP can exceed 4,000 m. However, the energy mechanism of its development is less understood. In this study, the energy mechanism of ABL development of three sites on the TP was analyzed using intensive sounding observation data from the Third Tibetan Plateau Atmospheric Scientific Experiment. The results showed that the surface sensible heat flux, boundary layer entrainment energy, and heat flux at the top of the ABL affected ABL growth. The ABL depths at the Shiquanhe and Gerze stations were relatively higher, with a mean height of approximately 2,500 m above ground level (agl) and a maximum of 4,500 m agl. The ABL grew to its highest height at 20:00 Beijing Time, and its residual layer was also deep. The ABL depths at the Jiulong station were mainly below 1,200 m agl. The accumulated surface sensible heat flux (62.5%) and residual layer entrainment energy (9.7%) significantly affected the ABL development at Shiquanhe station. In addition to the accumulated sensible heat flux and residual layer entrainment energy, the latent heat flux at the top of the boundary layer also significantly impacted the ABL development at Gerze station. The energy required for the ABL growth at Jiulong station was also the smallest, owing to its lowest depth here. The accumulated sensible heat flux played the most crucial role in boundary layer development over the TP. The influences of wind shear on ABL growth cannot be ignored.