Response of Indian Ocean intertropical convergence zone to southern Indian Ocean dipole

In this study, we discuss the influence of the Southern Indian OceanDipole (SIOD) on the location variation of the Intertropical Convergence Zone (ITCZ)over the Indian Ocean and its possible reasons using observations and the CommunityEarth System Model version 1.0.4 (CESM1.0.4). The results indicate that positiveSIOD (PSIOD) and negative SIOD (NSIOD) events in boreal winter have a considerableinfluence on the ITCZ location over the Indian Ocean in the following year,especially in boreal spring and summer. The observations suggest that the ITCZshifts northward in the following spring and summer after PSIOD events, while shiftssouthward after NSIOD events. Numerical simulations with CESM can well reproduce theobserved results. We further analyze the correlation between the winter sea surfacetemperature anomalies over the southern Indian Ocean in SIOD years and the ITCZlocation over the Indian Ocean during the following spring and summer, and theresults not only confirm that the PSIOD and the NSIOD drive the ITCZ to shiftnorthward and southward, respectively, but also prove that SIOD events show agreater impact on the Indian Ocean ITCZ location in the following spring and summer.In addition, numerical experiments show that the northeast SST of SIOD has a greaterimpact on ITCZ than the southwest SST. After NSIOD events, the Mascarene high andthe Australian high weaken in the following spring and summer, and northwesterlycross-equatorial flow anomalies appear in the equator around50°E-90°E. Moreover, there is remarkable and anomalous ascendingmotion over 0°S-20°S, and the ascending branch of the Hadleycirculation is southward. Simultaneously, a positive precipitation anomaly appearssouth of the equatorial Indian Ocean, and the ITCZ over the Indian Ocean movessouthward. However, after PSIOD events, the effects on the Indian Ocean ITCZlocation in the following spring and summer are roughly opposite to those of NSIODevents.