  We present a comparison between theoretical, frequency-dependent, damping
rates and linewidths of radial-mode oscillations in red-giant stars located in
the open cluster NGC 6819. The calculations adopt a time-dependent non-local
convection model, with the turbulent pressure profile being calibrated to
results of 3D hydrodynamical simulations of stellar atmospheres. The linewidths
are obtained from extensive peakbagging of Kepler lightcurves. These
observational results are of unprecedented quality owing to the long continuous
observations by Kepler. The uniqueness of the Kepler mission also means that,
for asteroseismic properties, this is the best data that will be available for
a long time to come. We therefore take great care in modelling nine RGB stars
in NGC 6819 using information from 3D simulations to obtain realistic
temperature stratifications and calibrated turbulent pressure profiles. Our
modelled damping rates reproduce well the Kepler observations, including the
characteristic depression in the linewidths around the frequency of maximum
oscillation power. Furthermore, we thoroughly test the sensitivity of the
calculated damping rates to changes in the parameters of the nonlocal
convection model.
