Simulated Change in the Interannual Variability of South Asian Summer Monsoon in the 21st Century

This study investigates the projected changes in interannual variability ofSouth Asian summer monsoon and changes of ENSO--monsoon relationships in the21st century under the Intergovernmental Panel on Climate Change (IPCC)scenarios A1B and A2, respectively, by analyzing the simulated results oftwelve Coupled Model Intercomparison Project Phase 3 (CMIP3) coupled models.The dynamical monsoon index (DMI) was adopted to describe the interannualvariability of South Asian summer monsoon, and the standard deviation (SD)was used to illustrate the intensity of interannual variability. It wasfound that most models could project enhanced interannual variability ofmonsoon in the 21st century. The multi-model ensemble (MME) results showedincreases in the interannual variability of DMI: 14.3% and 20.0% underscenarios A1B and A2, respectively. The MME result also showed increases inthe rainfall variability are of about 10.2% and 22.0% under scenariosA1B and A2. The intensification of interannual variability tended to occurover the regions that have larger variability currently; that is, ``thestrong get stronger'. Another finding was that ENSO--monsoon relationshipsare likely to be enhanced in the 21st century. The dynamical componentof the monsoon will be more closely correlated to ENSO in the future underglobal warming, although the ENSO--summer rainfall relationship cannot bereasonably projected by current models. This suggests that the South Asiansummer monsoon is more predictable in the future, at least dynamically.