  We study the $3~\mu$m scattering feature of water ice detected in the outer
disk of HD 142527 by performing radiative transfer simulations. We show that an
ice mass abundance at the outer disk surface of HD 142527 is much lower than
estimated in a previous study. It is even lower than inferred from far-infrared
ice observations, implying ice disruption at the disk surface. Next, we
demonstrate that a polarization fraction of disk-scattered light varies across
the ice-band wavelengths depending on ice grain properties; hence, polarimetric
spectra would be another tool for characterizing water-ice properties. Finally,
we argue that the observed reddish disk-scattered light is due to grains with a
few microns in size. To explain the presence of such grains at the disk
surface, we need a mechanism that can efficiently oppose dust settling. If we
assume turbulent mixing, our estimate requires $\alpha\gtrsim2\times10^{-3}$,
where $\alpha$ is a non-dimensional parameter describing the vertical diffusion
coefficient of grains. Future observations probing gas kinematics would be
helpful to elucidate vertical grain dynamics in the outer disk of HD 142527.
