A climate network perspective of the intertropical convergence zone

Abstract

Abstract. The intertropical convergence zone (ITCZ) is an important component of the tropical rain belt. Climate models continue to struggle to adequately represent the ITCZ and differ substantially in its simulated response to climate change. Here we employ complex network approaches, which extract spatio-temporal variability patterns from climate data, to better understand differences in the dynamics of the ITCZ in state-of-the-art global circulation models (GCMs). For this purpose, we study simulations with 14 GCMs in an idealized slab-ocean aquaplanet setup from TRACMIP – the Tropical Rain belts with an Annual cycle and a Continent Model Intercomparison Project. We construct network representations based on the spatial correlation pattern of monthly surface temperature anomalies and study the zonal mean patterns of different topological and spatial network characteristics. Specifically, we cluster the GCMs by means of their zonal network measure distribution utilizing hierarchical clustering. We find that in the control simulation, the zonal network measure distribution is able to pick up model differences in the tropical SST contrast, the ITCZ position and the strength of the Southern Hemisphere Hadley cell. Although we do not find evidence for consistent modifications in the network structure tracing the response of the ITCZ to global warming in the considered model ensemble, our analysis demonstrates that coherent variations of the global SST field are linked with ITCZ dynamics. This suggests that climate networks can provide a new perspective on ITCZ dynamics and model differences therein.

Response of the global ITCZ to different ENSO phases and how the ITCZ determined from the maximum precipitation compares with the surface tropical winds convergence

“…The sea surface temperatures (SSTs) influence the spatio-temporal dynamics of the ITCZ (Mischell & Lee, 2022;Wolf et al, 2020). Therefore, the seasonal position of the ITCZ which is an area of intense precipitation (Philander et al, 1996;Roldán-Gómez et al, 2022) and maximum surface wind convergence (Faulk et al, 2017), is plotted with an overlay of the seasonal SSTs and seasonal surface tropical winds for visual analysis of seasonal ITCZ and phases of ENSO (with their corresponding seasonal SSTs).…”

“…The intertropical convergence zone (ITCZ) is one of the most important, critical, and global rain bearing processes which is presently receiving continued research interest. There still exists a lot of knowledge gaps that merit further exploration about the ITCZ (Wolf et al, 2020). The understanding of the role of internal variability and external radiative forcing on the spatial position of the ITCZ is one of the open research questions.…”

“…This type of study is valuable because simulation of the ITCZ is an important element of research towards better representation of the ITCZ process by climate models (Wu et al, 2003). Climate models, to date, are struggling to consistently simulate and project the ITCZ features as informed by the future climate change projections based on different emission scenarios (Liu et al, 2020;Wolf et al, 2020). It is therefore important to continue developing a thorough understanding of the spatial responses of the ITCZ especially to slow drivers of climate variability to improve the model representation of the process.…”