An ensemble of atmospheric model simulations over the Greenland ice sheet has been conducted as part of a regional atmospheric reanalysis project. The model simulations were performed with the Polar MM5 mesoscale atmospheric model and were conducted in order to determine an appropriate model configuration for use in the regional atmospheric reanalysis. The ensemble consists of members that used multiple model physics options and data assimilation options. Results from this ensemble have been evaluated in terms of ice sheet averaged precipitation and evaporation over Greenland. Differences in the simulated ice sheet average precipitation and evaporation will be presented, and the results will be used to identify the degree of uncertainty in future simulations of ice sheet mass balance terms over the Greenland ice sheet.