On the validation of the simulation of early season precipitation on the island of Puerto Rico using a mesoscale atmospheric model

The ability of a mesoscale atmospheric model to reproduce the spatial distribution of the precipitation of the Caribbean island of Puerto Rico during an early rainfall season month (April) is evaluated in this paper, taking the month of April 1998 as the primary test case, and analyzed in detail with subsequent simulations for April 1993. The monthly accumulated rainfall was simulated using the Regional Atmospheric Modeling System (RAMS), and the results were validated with precipitation data from 15 cooperative stations located throughout the island. The monthlong numerical simulation for April 1998 replicated the observed precipitation pattern, including the general spatial distribution, and daily and monthly totals, to varying degrees of accuracy. At specific locations, errors ranged from 2% in the rainy mountains to 82% in the San Juan metropolitan area, with a general tendency of the model to produce lower precipitation values throughout the simulation domain. An error analysis proved that the accuracy of the simulation is independent of elevation. The station data showed two dominant precipitation events during the month of April 1998: one on 2 April and the other on 16 April. The model was able to replicate the precipitation observed during the first precipitation event with less precision than for the second event. This might be attributed to the model's inability to capture the large-scale forcing that produced the recorded amounts of rainfall observed during the second precipitation event. The results for total accumulated precipitation for April 1993 were very similar to the results for the April 1998 simulation, for both the spatial distribution and total values of rainfall.