Impact of an inhomogeneous density distribution on selected
  observational characteristics of circumstellar disks
  Context. The analysis of observations of circumstellar disks around young
stellar objects is often based on models with a smooth and continuous density
distribution. However, spatially resolved observations with increasing angular
resolution and dynamical models indicate that circumstellar disks are
highlystructured.
  Aims. We investigate the influence of different clumpy density distributions
on selected physical properties and observable characteristics of circumstellar
disks.
  Methods. Based on radiative transfer modelling we calculate the temperature
structure of the disk and simulate observational quantities in the thermal
re-emission and scattering regime. We compare our results to those obtained for
a smooth and continuous density distribution to quantify the influence of
clumps on physical parameters and observable quantities of circumstellar disks.
  Results. Within the considered model space, the clumpiness has a significant
impact on the disk temperature distribution. For instance, in the transition
region from the upper disk layers to the disk interior, it causes a decrease of
the mean temperature by up to 12 K. In addition, circumstellar disks with
clumpy density distributions feature a lower spectral index in the submm/mm
range of the SED. As a consequence of the lower spectral index, the dust grain
size derived from the submm/mm-slope of the SED may be overestimated, if the
inhomogeneity of the disk density distribution is not taken into account.
Furthermore, the scattered light brightness distribution of clumpy disks shows
a steeper radial decrease. Additionally, clumpy density distributions change
the degree of polarization of the scattered light in the optical.
