Interdecadal Shift in Dipole Pattern Precipitation Trends Over the Tibetan Plateau: Roles of Local Vortices

Abstract

Trends of precipitation over the Tibetan Plateau (TP) are characterized by a north-south dipole pattern, and the role of local mesoscale systems, TP vortices (TPVs), remains ambiguous. This work reports that the north-south dipole pattern trends in the TPVs-associated precipitation have experienced an interdecadal shift in the last two decades, that is, increases in northern TP and decreases in southern TP first and then varies opposite trends, which greatly contributes to the similar interdecadal shift in TP precipitation trends. Furthermore, the causes of changes in TPV frequency are explored from the perspective of lower troposphere conditions. We find that the lower-level winds, that is, zonal winds over the TP and meridional winds across the northwestern TP boundary, are responsible for the regionally different variations in TPV frequency. The variations in Indian Ocean Dipole are suggested to contribute to the changes in lower-level winds over the TP.