Interdecadal shift in dipole pattern precipitation trends over the Tibetan Plateau: Roles of local vortices

Tibetan Plateau (TP) has the highest elevation worldwide, and functions as an important modulator of both regional and global climates. Known as Asia’s water tower, TP is the headwater area of some major rivers, including the Yangtze River, Yellow River, Mekong River, Brahmaputra River, Ganges River, and Indus River. Precipitation over the TP exerts a great impact not only on local water resources but also on those downstream. Thus, variations in TP precipitation, especially their spatial pattern, are worth further study. In recent decades, the dipole pattern trends in precipitation over the TP has raised concerns, i.e., opposite precipitation trends in the northern TP (NTP) and in southern TP (STP). However, the physical processes of the variations in TP precipitation, especially the roles of local mesoscale systems, Tibetan Plateau vortices (TPVs), are not yet clear. In this work, dipole pattern variations are found in TPVs-associated precipitation, which experienced an interdecadal shift in the last two decades, that is, increases in NTP and decreases in STP first and then varies opposite trends. The interdecadal shift in the TPVs-associated precipitation trends greatly contributes to the interdecadal shift in the TP precipitation trends. Furthermore, the causes of variations in TPV frequency are explored, and find that the changes in zonal winds over the TP and the meridional winds across the northwestern TP boundary are closely related to the regionally different variations in TPV frequency. Subsequently, the changes in the sea surface temperature of India Ocean are demonstrated to be responsible for the wind variations.