Interdecadal change in the relationship between the Antarctic oscillation and autumn rainfall in the Yunnan-Guizhou plateau of Southwest China

The interdecadal change in the relationship between the Antarctic Oscillation (AAO) and autumn rainfall in the Yunnan-Guizhou Plateau of Southwest China is investigated by using the observed autumn rainfall data at 119 stations and the National Centers for Environment Prediction/National Center for Atmospheric Research reanalysis data for the period 1961-2021. Results show the AAO correlates well with the autumn rainfall in the Yunnan-Guizhou Plateau for the second period (2002-2021) because the AAO becomes stronger. The possible influencing mechanism of AAO on autumn rainfall in the Yunnan-Guizhou Plateau during 2002-2021 is related to the meridional teleconnection pattern and associated convection over the Philippine Sea. The positive AAO can trigger a meridional teleconnection pattern in the upper troposphere to propagate from the southern Pacific to northern Pacific and cause anomalous westerly over the tropical west Pacific, which inhibits the convection over the Philippine Sea. On the one hand, the weakened convection over the Philippine Sea causes the anomalous ascending motion over the Yunnan-Guizhou Plateau; on the other hand, it results in an anomalous anticyclone over the tropical Northwest Pacific and strengthens the transport of water vapor from the tropical Pacific to the Yunnan-Guizhou Plateau.