  A dimensionless collisionality scan has been performed in H-mode plasmas on
DIII-D tokamak, with detailed measurements of intermediate-to-high wavenumber
turbulence using Doppler backscattering systems. It is found that the shorter
wavelength turbulence develops into spatially asymmetric turbulent structures
with a long-radial-range correlation (LRRC) in the mid-radius region of
high-collisionality discharges. Linear \textsc{cgyro} simulations indicate that
the underlying turbulence is likely driven by the electron-temperature-gradient
(ETG) mode. The LRRC transport events are highly intermittent and show a power
spectrum of \(S_{\tilde{n}}(k_\perp) \propto k^{-1}_\perp\) for density
fluctuations, which is often associated with self-organized criticality. The
magnitude and the radial scale of those turbulent structures increase
significantly when the $E_{r}\times B$ mean flow shearing rate decreases. The
enhanced LRRC transport events appear to be correlated with the degraded energy
confinement time. The emergence of such LRRC transport events may serve as a
candidate explanation for the degrading nature of \emph{H}-mode core plasma
confinement at high collisionality.
