Observed changes in wintertime MJO under sea surface temperature war-ming in the tropical Indian and western Pacific Oceans and their impacts on precipitation in southern China
The Madden-Julian Oscillation(MJO)is the dominant mode of intraseasonal variability in the tropics and has been widely studied since its discovery by Madden and Julian in 1971.The tropical oceans are a critical source of moisture,and positive sea surface temperature(SST)anomalies enhance heating and moisture fluxes,which facilitate the initialization and propagation of the MJO.Observations reveal a significant warming trend in the tropical Indian Ocean and western Pacific(TWIP)since 1979,associated with anthropogenic greenhouse gas forcing.However,previous studies indicate that current climate models struggle to simulate MJO variability accu-rately,underscoring the challenges in understanding its role in weather and the climate systems.This study exam-ines the observed impacts of SST warming in the TWIP on the MJO,focusing on changes in its characteristics and their influence on winter precipitation in China from 1979 to 2012.South China,where precipitation is heaviest,has experienced a significant increase in rainfall since 1979,making it vital to investigate the contribution of MJO changes to this trend.The analysis reveals that SST warming in the TIWP intensifies heating and moisture fluxes,leading to an increase in MJO amplitude across all phases,with a statistical significant rise in phase 6.Vertical wa-ter vapor distribution changes result in an increased frequency of MJO phases,particularly phase 5,facilitating eastward propagation from phase 4 to phase 5 and prolonging phase 5 activity.These MJO changes are linked to enhanced subsidence in South China,associated with local Hadley cell dynamics,resulting in more negative sub seasonal precipitation anomalies during MJO phases 5 and 6 in recent decades.The findings provide observational evidence of the significant influence of SST warming on MJO activity and its subsequent impacts on regional precipitation patterns.The results highlight that MJO phase frequency chan-ges reflect shifts in preferred regions of activity and structural adjustments.Future research should employ state-of-the-art GCMs to explore the influence of SST warming on MJO in greater detail.This study focuses on climato-logical changes in MJO under TWIP basin-wide warming.Howe ver,variations in MJO structure and their differen-tial impacts on weather systems,warrant further diagnostic analysis.
MJOthe tropical Indian Ocean and the western Pacific OceanSSTmoistureHadley circulation
万方数据
维普
