A physically-refined regional climate model for the Tibetan Plateau

Reliable climate modeling of the Tibetan Plateau (TP) is essential for understanding the variability of the Asian monsoon, water resources, and associated energy and water cycles. However, accurately simulating the region's complex climate remains challenging for existing models, which often significantly overestimate precipitation and underestimate cold-season air temperatures. In this study, we introduce the Tibetan Plateau Climate System Model (TPCSM), also referred to as TP-WRF, developed from the Weather Research and Forecasting (WRF) model. We have enhanced or incorporated key physical processes related to terrain, land, lakes, snow, and clouds that are often poorly represented or missing in standard climate models. These refinements lead to a significant improvement in simulation accuracy. The wet bias in summer precipitation, averaged across weather stations, is reduced from 2.0 to 0.5 mm/d, primarily due to the implementation of a turbulent orographic form drag scheme and a probability cloud fraction scheme. Similarly, the cold bias in air temperature from winter to spring is nearly eliminated (from -1.8 ℃ to 0.1 ℃), largely attributable to improved parameterizations for shallow-snow albedo and the representation of complex terrain effects on snow cover. The TPCSM has contributed to two international model intercomparison projects and has been used to develop high-resolution meteorological datasets, thereby advancing our understanding of the TP's water and energy cycles. The development of TPCSM marks a significant step forward in regional climate modeling for complex terrain, with implications for improving water resource management, hazard forecasting, and climate change impact assessment across the Third Pole region.