Submitted to Journal of Climate: May-11-2010 Revised for Journal of Climate: December-15-2010

The NCAR-Community Climate System Model version 4 (CCSM4) includes a new dynamical core option based on NCAR’s High-Order Method Modeling Environment (HOMME). HOMME is a petascale capable high-order element-based conservative dynamical core developed on the cubed-sphere grid. Initial simulations have been completed in aqua-planet configuration of CAM4, the atmospheric component of CCSM4. We examined the results of this simulation and assessed its fidelity in simulating rainfall, which is one of the most important components of the Earth’s climate system. For this we compared the results from two other dynamical cores of CAM4, the finite volume (FV) and Eulerian (EUL). Instantaneous features of rainfall in HOMME are similar to FV and EUL. Similar to EUL and FV, HOMME simulates a single peak Inter Tropical Convergence Zone (ITCZ) over the equator. The strength of the ITCZ is found to be almost same in HOMME and EUL but more than that in FV. It is observed that in HOMME and EUL there is higher surface evaporation, which supplies more amount of moisture into the deep tropics an