Effects of cloud microphysics on the simulation of extreme precipitation over the Tibetan Plateau region

Extreme precipitation plays a critical role in the development of hydrological extremes with severe socio-economic and environmental impacts. Over the Tibetan Plateau (TP), extreme precipitation events have increased in frequency and intensity and are projected to rise further under climate change. However, simulations of such events in this region remain challenging due to uncertainties in the representation of cloud microphysics. While previous research has exposed the sensitivity of climate models to microphysics schemes, the atmospheric processes driving discrepancies in precipitation simulations are still not fully explored. In this study, we analyse two extreme precipitation events over the TP region using six different microphysics schemes in the Weather Research and Forecasting model (WRF). We assess how precipitation and related processes are represented across these schemes and identify key sources of uncertainties in precipitation simulations. Our findings reveal substantial variations in the location, intensity and timing of precipitation, with differences in accumulated amounts reaching up to 40 % depending on the microphysics scheme used. Further analysis shows that the timing and strength of convective activity are closely linked to precipitation patterns, leading to significant discrepancies across experiments. Additionally, the representation of horizontal water vapour transport plays a critical role in determining the location and intensity of precipitation by influencing moisture availability. Lastly, the modelling of cloud composition – particularly of solid-phase hydrometeors – emerges as a crucial factor in precipitation evolution, contributing substantially to the variability in simulated precipitation location and intensity.