Energetic Constraints on the ITCZ position in the Observed Seasonal Cycle from MERRA-2 Reanalysis

Idealized simulations show that the approximate colocation between the ITCZ and the energy flux equator (EFE), which holds on the annual and zonal average, breaks down on subseasonal timescales, as the Hadley cell develops a shallow return ow and negative gross moist stability (GMS). Here, we explore if similar mechanisms are seen in re-analysis data. In the zonal mean, a temporal offset exists between the ITCZ and the EFE as the ITCZ is retreating from the northern to the southern hemisphere and the Hadley cell transports energy northward across the equator despite a northward-shifted ITCZ. At these times, the southern cell has a bottom-heavy structure, with a distorted cell boundary and northward energy transport. In the Eastern Pacific, while bottom-heavy structures exist throughout the year, the bottom heaviness is stronger at times with negative GMS, and weak SSTs and large negative SST Laplacian below the ITCZ.