  We study the influence of low-level water and high-level ice clouds on
low-resolution reflection spectra and planetary albedos of Earth-like planets
orbiting different types of stars in both the visible and near infrared
wavelength range. We use a one-dimensional radiative-convective steady-state
atmospheric model coupled with a parametric cloud model, based on observations
in the Earth's atmosphere to study the effect of both cloud types on the
reflection spectra and albedos of Earth-like extrasolar planets at low
resolution for various types of central stars. We find that the high scattering
efficiency of clouds substantially causes both the amount of reflected light
and the related depths of the absorption bands to be substantially larger than
in comparison to the respective clear sky conditions. Low-level clouds have a
stronger impact on the spectra than the high-level clouds because of their much
larger scattering optical depth. The detectability of molecular features in
near the UV - near IR wavelength range is strongly enhanced by the presence of
clouds. However, the detectability of various chemical species in
low-resolution reflection spectra depends strongly on the spectral energy
distribution of the incident stellar radiation. In contrast to the reflection
spectra the spectral planetary albedos enable molecular features to be detected
without a direct influence of the spectral energy distribution of the stellar
radiation. Here, clouds increase the contrast between the radiation fluxes of
the planets and the respective central star by about one order of magnitude,
but the resulting contrast values are still too low to be observable with the
current generation of telescopes.
