The NCEP regional spectral model (RSM) has been found to have a smooth lateral boundary from the previous publications. A few study of it included some sensitivities of it lateral boundary treatment (Juang and Kanamitsu 1994). The paper of Warner et al 1997 gave us a mortivation to investigate more on the sensitivities of the RSM lateral boundary.

The preliminary investigation from the previous publication of RSM, we can see that RSM lateral boundary was performed differently from other models. It may be related to the perturbation nesting, which is different from other models. Several experiments were designed to address some points discussed in Warner et al 1997 and perturbation nesting in RSM.

The experiment with similar resolution between RSM and GSM showed a success of the perturbation nesting. It has negligibly small perturbation up to 3 days forecast. The experiement with different domain sizes indicates that RSM is better than GSM for all different sizes, eventhough the larger the domain the better the performance. The root-mean-square differences of some fileds were computed and compared to those in Warner et al 1997. The results from the comparison indicated that RSM had much smaller error than others. It comes to a conclusion that RSM nesting strategy generates negligible error along the lateral boundary, so the lateral boundary influence is minimized by RSM nesting strategy. It is good for regional or mesoscale modeling.