Satellite latent heating retrievals uncover a seasonal terrain-monsoon seesaw in southern Tibetan Plateau rainfall

The relative roles of the Himalayan orography and South Asian summer monsoon (SASM) circulation in Tibetan Plateau (TP) precipitation remain contentious, yet numerical simulations exhibit substantial uncertainties due to extreme topographic gradients. Conventional satellites capture only exterior cloud properties or precipitation particle quantification, missing cloud-internal heating and updrafts. Using a novel satellite retrieval, we resolve the vertical structure of latent heating (LH) within precipitating clouds along the Himalayan slopes, offering new insight into precipitation drivers in this critical region. Satellite observations show that in spring, the altitude of peak latent heat (APLH) follows the southern slope topography, reflecting strong orographic control. Model results reveal that surface sensible heating below 2 km and orographic uplift above 2 km together enhance vertical motion and precipitation. In summer, however, the APLH stabilizes near 6 km across the southern Plateau, pointing to diminished local forcing and dominant large-scale monsoon control. The SASM supplies warm, moist air via mid-tropospheric moisture transport, bypassing terrain lifting and surface heating. These findings reveal a terrain-monsoon “seesaw” in Himalayan cloud-precipitation processes, characterized by a seasonal shift in dominance from local orographic forcing before the onset of the SASM to large-scale monsoonal circulation after the onset. This perspective provides broader insights into mountain-monsoon water cycle interactions worldwide.