Intrinsic Coupled Ocean-Atmosphere Modes of the Asian Summer Monsoon: A Re-assessment of Monsoon-ENSO Relationships

摘要: Using global rainfall and sea surface temperature (SST) data for the past two decades (1979-1998), we have investigated intrinsic modes of Asian summer monsoon (ASM) ENSO co-variability. Three recurring ASM rainfall-SST coupled were identified. The first is a basin scale mode that features SST variability over entire tropics (including region), identifiable with those occurring during El Nino or La Nina. This further characterized by pronounced biennial variation in associated fluctuations anomalous Walker circulation occur Nino/La Nina transitions. second comprises mixed regional basin-scale signals, intraseasonal interannual variabilities. pattern developing Nina, low level anticyclone subtropics western Pacific off coast East Asia. third depicts an east-west dipole across southern equatorial Indian Ocean, most likely stemming from ocean-atmosphere processes within region. also possesses decadal time linear trend, which are not variability. Possible causes year-to-year sub-regions been evaluated reconstruction observed singular eigenvectors modes. It found while can account portions events (up to 60% 1998), accounts up 20-25% typical non-ENSO years. Stronger monsoon-ENSO relationship tends boreal immediately preceding i.e., 1998, 1988 1983. Based on these results, discuss possible impacts via west articulate hypothesis wind forcings derived may be instrumental inducing strong modulation natural cycles.