The influence of complex terrain on cloud and precipitation on the foot and slope of the southeastern Tibetan Plateau

As an essential moisture transport channel over the Tibetan Plateau (TP), accurate simulation of precipitation over the southeastern TP (SETP) is crucial for downstream moisture transport and water resource assessment. To improve SETP’s precipitation simulation accuracy, a Turbulent Orographic Form Drag (TOFD) scheme, which represents the TOFD effect of subgrid orography on model grids, is employed. The impact of TOFD on cloud and precipitation during the summer monsoon over the SETP is investigated from dynamical and cloud microphysical perspectives. Through comparison with ground observations and satellite precipitation data, TOFD reduces the simulated precipitation bias. Despite reducing moisture transport, TOFD enhances low-level convergence and high-level divergence by influencing the low-level wind, thereby strengthening updraft and cloud and precipitation processes before the slope of SETP. TOFD also increases total precipitation before the slope by promoting heavy precipitation and reducing weak precipitation. However, TOFD diminishes the updraft and cloud and precipitation processes over the slope of SETP by influencing low-level wind. The reduced moisture transport by TOFD leads to decreased precipitation over the slope. Additionally, TOFD reduces total precipitation over the slope by promoting weak precipitation and reducing heavy precipitation. Furthermore, the impact mechanism of TOFD on precipitation depends on the wind speed, which is weakened during weak precipitation period with reduced wind speed and enhanced during heavy precipitation period with increased wind speed. These findings enhance the understanding of the complex terrain's influence on cloud and precipitation and provide a basis for improving cloud and precipitation simulation over the SETP.