Transient simulation of the Tibetan Plateau modulated distinct orbital-scale precipitation variation in East and South Asia

The insolation change caused by the Earth's orbital forcing is known to play an important role in regulating variations of the Asian monsoon at various time scales. Geological records and numerical simulation revealed that the climate change in the Asian monsoon region was in-phase or out-of-phase with the boreal summer insolation at the orbital scale. Using the Community Climate System model version 3 and the orbital acceleration technique, we conducted two long-term transient simulations with and without the Tibetan Plateau (TP) orography (TP1 and TP0 experiments). The main objective of this study was to examine the influence of the TP uplift on the orbital-scale precipitation in East and South Asia, and the anti-phase relationship between southern and northern East Asia (SEA and NEA), during the past 150 kyr. The results further confirm that the uplift of the TP significantly affects the Asian atmospheric circulation and precipitation, and is an amplifier of the Asian summer monsoon at the precessional scale. In general, the presence of the TP causes the rain belt and atmospheric circulation front to shift northward. In particular, we found that the anti-phase relationship of precipitation between NEA and SEA at the precessional band is also controlled by the uplift of the TP. Simulations in TP1 and TP0 experiments show that the inverse variations in atmospheric circulation, including the 850 hPa wind field and vertical pressure velocity caused by the uplift of the TP, can directly lead to the out-of-phase JJA precipitation at the precessional scale between NEA and SEA. Future research to collect various climatic proxies with high spatial and temporal resolutions, at least since the Cenozoic, is required to support the simulation results of this study.