  Spatially resolved observations of molecular line emission have the potential
to yield unique constraints on the nature of turbulence within protoplanetary
disks. Using a combination of local non-ideal magnetohydrodynamic simulations
and radiative transfer calculations, tailored to properties of the disk around
HD 163296, we assess the ability of ALMA to detect turbulence driven by the
magnetorotational instability (MRI). Our local simulations show that the MRI
produces small-scale turbulent velocity fluctuations that increase in strength
with height above the mid-plane. For a set of simulations at different disk
radii, we fit a Maxell-Boltzmann distribution to the turbulent velocity and
construct a turbulent broadening parameter as a function of radius and height.
We input this broadening into radiative transfer calculations to quantify
observational signatures of MRI-driven disk turbulence. We find that the ratio
of the peak line flux to the flux at line center is a robust diagnostic of
turbulence that is only mildly degenerate with systematic uncertainties in disk
temperature. For the CO(3-2) line, which we expect to probe the most
magnetically active slice of the disk column, variations in the predicted
peak-to-trough ratio between our most and least turbulent models span a range
of approximately 15%. Additional independent constraints can be derived from
the morphology of spatially resolved line profiles, and we estimate the
resolution required to detect turbulence on different spatial scales. We
discuss the role of lower optical depth molecular tracers, which trace regions
closer to the disk mid-plane where velocities in MRI-driven models are
systematically lower.
