  In a quasi-1D thermal convective system consisting of a large array of
nonlinearly coupled oscillators, clustering is the way to achieve a regime of
mostly antiphase synchronized oscillators. This regime is characterized by a
spatiotemporal doubling of traveling modes. As the dynamics is explored beyond
a spatiotemporal chaos regime with weak coupling, new interacting modes emerge
through a supercritical bifurcation. In this new regime, the system exhibits
coherent subsystems of antiphase synchronized oscillators, which are stationary
clusters following a spatiotemporal beating phenomena. This regime is the
result of a stronger coupling. We show from a phase mismatch model applied to
each oscillator, that these phase coherent domains undergo a global phase
instability meanwhile the interactions between oscillators become nonlocal. For
each value of the control parameter we find out the time-varying topology (link
matrix) from the contact interactions between oscillators. The new
characteristic spatiotemporal scales are extracted from the antiphase
correlations at the time intervals defined by the link matrix. The
interpretation of these experimental results contributes to widen the
understanding of other complex systems exhibiting similar phase chaotic
dynamics in 2D and 3D.
