  Numerous observational evidence has suggested the presence of active
meteorology in the atmospheres of brown dwarfs. A near-infrared brightness
variability has been observed. Clouds have a major role in shaping the thermal
structure and spectral properties of these atmospheres. The mechanism of such
variability is still unclear and both 1D and global circulation model cannot
fully study this topics due to resolution. In this study, a convective
resolving model is coupled to grey-band radiative transfer in order to study
the coupling between the convective atmosphere and the variability of clouds
over a large temperature range with a domain of several hundreds of kilometers.
Six types of clouds are considered, with microphysics including settling. The
clouds are radiatively active using Rosseland mean coefficient. Radiative cloud
feedback can drive spontaneous atmospheric variability in both temperature and
cloud structure, as modeled for the first time in three dimensions. Silicate
clouds have the most effect of the thermal structure with the generation of a
secondary convective layer in some cases, depending on the assumed particle
size. Iron and Aluminum clouds also have a substantial impact on the
atmosphere. Thermal spectra were computed, and we find the strongest effect of
clouds is the smoothing of spectral features at optical wavelengths. Compared
to observed L and T dwarfs on color-magnitude diagram, the simulated
atmospheres are redder for most of the cases. The simulations with the presence
of cloud holes are closer to the observations.
