Abstract: In this study, we used monthly averaged ERA-Interim reanalysis datasets and SWOOSH (Stratospheric water and ozone satellite homogenized) water vapor data to analyze the interannual geographic pattern of water-vapor-mass anomalies in the 340–360 K layers and its maintenance over the Tibetan Plateau (TP) region in July–August. Results show that interannual variations in the geographic patterns of water-vapor-mass anomalies have three dominant modes, namely, uniform, abnormal east–west dipole, and south–north dipole modes. In association with the positive phase of the uniform mode, that is, more water vapor mass over the entire TP area, stronger convective and upward diabatic water-vapor-mass transport over the TP region leads to an enhanced convergence of the water vapor mass. The strengthened South Asian high (SAH) results in an enhanced divergence and convergence of the adiabatic water-vapor-mass transport over the TP and to its west. The opposite occurs when there is less water vapor mass over the entire TP area. For the positive phase of the east–west diploe mode when the water vapor mass is more/less in the west/east of the TP area, the convective and diabatic water-vapor-mass transport, and the convergence and divergence of diabatic and adiabatic water vapor mass in the upper troposphere all enhanced over the western TP but weakened over the central and eastern TP. Meanwhile, the center of the SAH shifts westward, giving rise to an abnormal westward adiabatic water-vapor-mass transport and contribute to the abnormal convergence of water vapor mass from the TP to the Iranian Plateau in the upper troposphere. When the water vapor mass is less/more in the west/east of the TP area, the results are opposite. For the positive phase of the south–north dipole mode when the water vapor mass is more/less in the northern/southern TP, the center of the SAH shifts northward, giving rise to an abnormal northward adiabatic water-vapor-mass transport in the northern TP in the upper troposphere and a stronger upward diabatic water-vapor-mass transport in the lower layers, which both lead to abnormal convergence of the water vapor mass. In contrast, the divergence of adiabatic water-vapor-mass transport and the convergence of diabatic water-vapor-mass transport are weakened in the southern TP, and vice versa when less/more water vapor mass occurs in the northern/southern TP.