  Recent X-ray observations of blue-shifted absorption lines revealed an
existence of the extremely fast disk winds with outflow velocities of
~0.1-0.3c. Such fast outflows would have a large impact on the coevolution of
black holes and host galaxies since they are expected to carry a large amount
of kinetic energy. One of the common characteristics of these fast winds is a
strong time variability of the absorption feature. To investigate this
variability, we have developed a new X-ray spectral model of the disk winds,
which is generated by 3-dimensional Monte Carlo radiation transfer simulations
on the assumption of the realistic wind geometry. By applying our wind model to
the multi-epoch X-ray data of an archetypal wind source PDS 456, we find the
variability in the absorption line is explained by a change of the wind
outflowing angle without any large variability in the mass outflow rate of the
wind. This result indicates that the fast disk winds are stable and that local
hydrodynamic instabilities produce a large time variability of the absorption
line. Moreover, we also apply our wind model to the disk-line source 1H
0707-495. The characteristic Fe-K feature in this source is successfully
reproduced our disk wind model for all the observations.
