This study investigates the thermal and moisture transport processes between two hydrologically distinct regions of the Tibetan Plateau (TP) during the warm season (May–September): the endorheic region- lake-rich hinterland TP, and the exorheic region- the Source Region of the Three Rivers (SRTR). Using ERA5 reanalysis and MODIS products (2013–2023), a water vapor transport mechanism is proposed between the hinterland TP and SRTR under specific conditions. This transport mechanism involves three steps: water vapor being uplifted over the lake group region, eastward advection due to westerly flow, and sinking in the SRTR. For the first stage, the water vapor near the surface is uplifted to a high level due to the strong surface sensible heating. Then, the water vapor can be transported to the mid-upper troposphere (450–500 hPa) and is carried by the westerly flow downstream. The transported water vapor can serve as an important supply for the heavy precipitation process of the SRTR. This result suggests that, despite belonging to separate hydrological basins, the lake group region of the TP can export moisture to the SRTR under specific circulation patterns and affect the precipitation of the downstream. This water transport reveals a previously overlooked cross-basin vapor redistribution process, offering new insights into the TP water cycle.

Water vapor transport; Cloud and Precipitation; the hinterland Tibetan Plateau; The Source Region of Three Rivers, Water cycle