An application of the spectral nudging technique to the simulation of summer precipitation over East Asia using a regional climate model: The impact of domain size and position

The sensitivity of a regional climate model (RCM) in modeling summer precipitation over East Asia to domain choice is tested using the model PSU-NCAR MM5v3. The effect of interior (spectral) nudging is also assessed. The RCM simulations are evaluated against the NCEP/NCAR Reanalysis data. The results are: (1) the MM5 is able to simulate the distribution and magnitude of summer precipitation though with some biases. The biases increase with increasing domain area, and thus domain choice has a significant influence on model’s simulations. Moreover, the RCM simulations have some biases near the domain boundaries, and thus are sensitive to the position of domain. (2) By using interior (spectral) nudging, the performance of the MM5 shows large improvements that increase with increasing domain areas. Therefore, the RCM can reproduce more realistic large-scale circulations, seasonal mean precipitation fields and the intra-seasonal (daily) variability, and, the sensitivities of the RCM simulations to the choice model domain are reduced as well.