The resolution and dynamical core dependence of the statistics of atmospheric river events in Community Atmospheric Model is examined. Aqua-planet simulations are run at 240, 120, 60 and 30 km grid-spacings using High-Order Methods Modeling Environment (HOMME) and Model for Prediction Across Scales (MPAS) dynamical cores with CAM4 physics. The frequency of atmospheric river events decreases with model resolution. This sensitivity is found to be related to the overall sensitivity of global atmospheric precipitable water content and its vertical profile as well as latitudinal location of the sub-tropical jets to model resolution. The pole-ward shift of the sub-tropical jets is found to be the leading cause for the reduction of AR frequency with increased resolution. Furthermore, the simulations are used to estimate the contribution of the tropical heating variability to the circulation patterns that drive atmospheric rivers. Equatorially centered heating anomalies are found to contribute about 30% of the stream function peak associated with ARs, suggesting some roles of tropical-extratropical interactions in the development of AR.