Numerical simulation is based on AFM data of surface morphology of silicon carbide field emission array (FEA) with two-tier microstructure made by SPETU LETI technology. Using COMSOL Multiphysics, the procedure for import AFM data into simulation environment is developed and the corresponding mathematical model of emission surface is constructed. Numerical model is investigated for computational mesh convergence using the calculation of electric field strength distribution by the finite element method. The optimal size of finite elements is revealed, at which the best convergence of the numerical solution is achieved, and AFM data interpolation parameters are investigated.