|Title||Indian Ocean variability in the CMIP5 multimodel ensemble: The basin mode|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Authors||Du Y., Xie SP, Yang Y.L, Zheng XT, Liu L., Huang G|
|Journal||Journal of Climate|
|Type of Article||Article|
|Keywords||Atmosphere-ocean interaction; atmospheric bridge; climate models; Climate variability; el-nino; enso; evaluation; Indian Ocean; indo-western pacific; interannual variability; model; northwest pacific; pacific; performance; sea-surface temperature; seychelles dome; southern oscillation; tropical|
This study evaluates the simulation of the Indian Ocean Basin (IOB) mode and relevant physical processes in models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Historical runs from 20 CMIP5 models are available for the analysis. They reproduce the IOB mode and its close relationship to El Nino-Southern Oscillation (ENSO). Half of the models capture key IOB processes: a downwelling oceanic Rossby wave in the southern tropical Indian Ocean (TIO) precedes the IOB development in boreal fall and triggers an antisymmetric wind anomaly pattern across the equator in the following spring. The anomalous wind pattern induces a second warming in the north Indian Ocean (NIO) through summer and sustains anticyclonic wind anomalies in the northwest Pacific by radiating a warm tropospheric Kelvin wave. The second warming in the NIO is indicative of ocean-atmosphere interaction in the interior TIO. More than half of the models display a double peak in NIO warming, as observed following El Nino, while the rest show only one winter peak. The intermodel diversity in the characteristics of the IOB mode seems related to the thermocline adjustment in the south TIO to ENSO-induced wind variations. Almost all the models show multidecadal variations in IOB variance, possibly modulated by ENSO.
Simulations of the Indian Ocean basin and its relationship to El Nino–Southern Oscillation (ENSO) in multiple models match well with observations of north Indian Ocean, showing that the models are doing a good job of simulating key processes involved. Better understanding of the Indian Ocean-ENSO linkage will improve climate predictability for the northwest Pacific Ocean and highly populated East Asia.