On time variability and other complications in studying the UV broad
  absorption lines of quasars: results from numerical simulations of radiation
  driven disk winds
  We review the main results from axisymmetric, time-dependent hydrodynamical
simulations of radiation driven disk winds in AGN. We illustrate the capability
of such simulations to provide useful insights into the three domains of
observational astronomy: spectroscopy, time-variability, and imaging.
Specifically, the synthetic line profiles predicted by the simulations resemble
the broad absorption lines observed in quasars. The intrinsically time
dependent nature of radiation driven disk winds that have been predicted by the
simulations can be supported by a growing number of the observed dramatic
variability in the UV absorption lines. And finally, the intensity maps
predicted by the simulations give physical and geometrical justification to the
phenomenologically deduced fact that a proper interpretation of the observed
line absorption requires the wind covering factor to be considered as being
partial, inhomogeneous, and velocity dependent.
