Lagged relationships between ENSO and the Asian Summer Monsoon in the CSIRO coupled model

The lagged relationship between the El Nino-Southern Oscillation (ENSO) and Asian Summer Monsoon (ASM) variability is investigated using the Commonwealth Scientific and Industrial Research Organization (CSIRO) Mark3 coupled model. Composite analyses of 17 warm and 16 cold events from an extended unforced run reveal that the model captures the asymmetric structures of rainfall and SST anomalies over the tropical Indian Ocean during northern hemisphere spring which is one of the major precursory signals of anomalous ASM variability. As a remote forcing mechanism prior to the ASM onset, simulated anomalous convection over the northern Indian Ocean strongly influences the land surface hydrologic conditions over central and southwest Asia. Simulated land-surface processes result in anomalous temperatures over the land, which in turn produce a change in the land-ocean thermal contrast over the domain. The results are consistent with observed features, which show a delayed and indirect impact of ENSO on the ASM variability during the early summer monsoon period, but not during the rest of the monsoon season.