A Comparative Study of Luzon Rainfall Simulations with the MM5 and the RegCM3 Models

The performance of the MM5 and the RegCM3 models in simulating total monthly rainfall has been evaluated. Total rainfall for the two months of June 2000 and June 2001 are simulated. June 2000 is a relatively dry month while June 2001 is a wet month. Simulations are made with different schemes for parameterizing cumulus convective rainfall for both models. Two schemes are tested for the MM5 simulations while four schemes are tested for the RegCM3 model. It is found that the rainfall simulations are highly dependent to the parameterization scheme. The results of the evaluation show that the MM5 model performs much better than the RegCM3 model.

The performance of the two models also depends on the characteristics of the weather situation which prevails during the month. The highest correlation for June 2000 between simulated and observed rainfall is done by the MM5 Betts-Miller scheme (0.8). On the other hand, this same model configuration performs badly for June 2001. The corresponding correlation is only 0.2. The reason for this poor performance for June 2001 is presumably due to the fact the model has been unable to predict accurately the weather disturbances which occurred during the month.

[Presented at the Samahang Pisika ng Pilipinas (SPP) Congress, 2005.]