What induces the interdecadal shift of the dipole patterns of summer precipitation trends over the Tibetan Plateau?

Precipitation on the Tibetan Plateau (TP) exert great impacts on the energy, water cycle, and regional ecosystem. But due to the wide differences in climate regimes and complicated topography, TP precipitation is characterized as greater spatial diversity and lower confidence of temporal tendency. Based on the precipitation datasets from in situ observations, reanalysis, and satellites, this study identifies the interdecadal shift of the summer precipitation trends in the southern and northern TP, which corresponds well with the remarkable changes of TP lakes area in recent years. The statistical results indicate that the TP summer precipitation has experienced an interdecadal transition in the late 1990s, with precipitation increasing and then decreasing in the southern TP, and decreasing and then increasing in the northern TP. Further analyses suggest that the changes in moisture budget and convection activities play an important role in the interdecadal variations of precipitation in the northern and southern TP, respectively. More specifically, the variations in the southern TP are contributed largely by the persistent weakening sensible heat source, which can depress the ascending motion and hinder the northward moisture transport in the southern TP. While in the northern TP, both observations and model sensitivity experiments indicate that the co-effect of the cold interdecadal Pacific oscillation (IPO) and warm Atlantic multidecadal oscillation (AMO) has profound impacts on the decadal shift of the net moisture budget in the northern TP. Specifically, the AMO can impact the Lake Baikal anticyclone through the anomalous wave propagation and then decrease the moisture output in the eastern TP. While the IPO can weaken the climatological westerlies and prompt the moisture to get stuck in the northern TP. Consequently, the variations in the net moisture budget can give rise to the decadal variations in summer precipitation in the northern TP.

Automated summary

The study on precipitation trends in the Tibetan Plateau reveals significant interdecadal changes in the past few decades, which are closely related to the changes in the area of TP lakes. The southern TP has experienced an increasing-then-decreasing trend in precipitation, while the northern TP has shown a decreasing-then-increasing trend. The changes in the southern TP are mainly attributed to the weakening sensible heat source, while the northern TP is influenced by the cold interdecadal Pacific oscillation (IPO) and warm Atlantic multidecadal oscillation (AMO).