Dependence of inter-hemispheric teleconnections on the climatological ITCZ pattern

Extratropical forcing can generate strong non-local responses via teleconnections. For example, the Hadley circulation responds to high-latitude forcing by shifting its ascending branch, the intertropical convergence zone (ITCZ), towards the warmer hemisphere. However, the ITCZ location has been shown to modulate the inter-hemispheric communication of an extratropical surface anomaly through the ITCZ blocking mechanism.
In this study, we investigate how the climatological ITCZ position affects the climate response to extratropical forcing. We conduct aquaplanet slab ocean simulations in MPI-ESM by imposing a southern hemispheric extratropical cooling of 50 Wm^-2 to five control states, each differing in the ITCZ location. 
Results show that the Hadley cell response and consequent ITCZ northward shift are the largest when the climatological ITCZ is in the same hemisphere as the forcing.  Both responses progressively weaken as the climatological ITCZ is displaced northward.
The amplitude and progressive weakening of the atmospheric response are shaped by the cloud radiative effect (CRE). If the ITCZ lies in the forced hemisphere, extratropical low-cloud formation enhances the imposed cooling locally, thus increasing the atmospheric compensation for the energetic imbalance. However, when the ITCZ is in the opposite hemisphere, a weak but positive low-cloud anomaly extending equatorward from the forced extratropics results in a dampened atmospheric compensation.
Locking the clouds mutes the atmospheric response, further highlighting the role of cloud feedbacks for ITCZ shifts.
Furthermore, we show that the negative sea surface temperature (SST) anomaly originating in the forced extratropics does not extend substancially beyond the ITCZ, reinforcing the idea that the ITCZ location limits the propagation of surface signals. We propose that changes in latent heat fluxes tied to the surface-wind response to the forcing are at the core of the ITCZ blocking mechanism, as an anomalous increase (decrease) in wind speed southward (northward) of the new ITCZ location leads to an enhancement (reduction) of the negative SST anomaly.
Our findings reveal that the ITCZ location and blocking effect strongly modulate extratropical-tropical interactions, implying that model biases in the ITCZ location might produce inaccurate responses to high-latitude forcing.