Downscaled Climate Change Impacts on Reference Evapotranspiration and Rainfall Deficits in Puerto Rico

The purpose of this study was to estimate reference evapotranspiration (ET_o) and rainfall excess (rainfall — ET_o) under climate change conditions for three locations in Puerto Rico: Adjuntas, Mayagüez and Lajas. Reference evapotranspiration was estimated by the Penman-Monteith method. Rainfall and temperature data were statistically downscaled from predictions obtained from the DOE/NCAR PCM global circulation model. The B1 (low), A2 (mid-high) and Alfi (high) emission scenarios of the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios were evaluated. Results from the analysis indicate that the rainy season will become wetter and the dry season will become drier. The average estimated rainfall excess (i.e., rainfall — ET_o > 0) for all scenarios and locations increased in September (the wettest month) to 356.4 mm for the year 2090 relative to an average rainfall excess of 149.8 mm for 2000. The average rainfall deficit (i.e., rainfall — ETo < 0) in February increased to –72.1 mm for the year 2090 relative to an average rainfall deficit of –26.1 mm for 2000. The implications of these results suggest that additional water could be saved during the wet months, which would be needed to offset increased irrigation requirements during the dry months.