Seasonal and interannual variations of the intertropical convergence zone over the Indian Ocean based on an energetic perspective

Abstract

The climate of tropical regions is significantly affected by migration of the intertropical convergence zone (ITCZ) whose location can be understood based on an energetic perspective. The ITCZ location depends on the cross-equatorial atmospheric energy transport (AET) and the equatorial net energy input ($$\hbox {NEI}_0$$). Using ERA-Interim dataset for the period 1980–2018, the ITCZ location over the Indian Ocean in different seasons and its migration are investigated. The cross-equatorial AET and the $$\hbox {NEI}_0$$ over the Indian Ocean are analyzed to determine the location of the ITCZ based on the atmospheric energy balance. Based on zonal mean maximum precipitation, the annual mean location of the ITCZ over the Indian Ocean is found in the Southern Hemisphere (approximately at 5.5$${}^{\circ }$$ S), while in some seasons, a double ITCZ forms. During the period 1980–2018, the annual mean location of the ITCZ over the Indian Ocean has migrated toward the equator by approximately 1$${}^{\circ }$$, although it is not statistically significant. The largest meridional migration of the ITCZ over the Indian Ocean occurs with the period of 12 months, showing seasonal migration of the ITCZ associated with the monsoon circulation. The location of maximum precipitation over the Indian Ocean is different from that of the energy flux equator (EFE), such that the EFE is always located north of the location of maximum precipitation. This is partly due to the fact that only the mean meridional circulation (MMC) component of the energy flux is considered to compute the EFE. Variations of the cross-equatorial AET and the Oceanic Nino Index (ONI) are not consistently correlated, while variations of the $$\hbox {NEI}_0$$ over the Indian Ocean and the ONI are quite consistent. Over the Indian Ocean, variation of the cross-equatorial AET dominates interannual variation of the ITCZ location, while variation of the $$\hbox {NEI}_0$$ dominates seasonal variation of the ITCZ location.