Trends in total rainfall, heavy rain events, and number of dry days in San Juan, Puerto Rico, 1955-2009
Pablo A. Méndez-Lázaro, Faculty of Biosocial Sciences and Graduate School of Public Health, and Department of Environmental Health, University of Puerto Rico-Medical Sciences Campus
Alejandro Nieves-Santiango, Graduate School of Public Health and Center for Public Health Preparedness, University of Puerto Rico-Medical Sciences Campus
Julieanne Miranda-Bermúdez, Graduate School of Public Health and Center for Public Health Preparedness, University of Puerto Rico-Medical Sciences Campus
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Climate variability is a threat to water resources on a global scale and in tropical regions in particular. Rainfall events and patterns are associated worldwide with natural disasters like mudslides and landslides, meteorological phenomena like hurricanes, risks/hazards including severe storms and flooding, and health effects like vector-borne and waterborne diseases. Therefore, in the context of global change, research on rainfall patterns and their variations presents a challenge to the scientific community. The main objective of this research was to analyze recent trends in precipitation in the San Juan metropolitan area in Puerto Rico and their relationship with regional and global climate variations. The statistical trend analysis of precipitation was performed with the nonparametric Mann-Kendall test. All stations showed positive trends of increasing annual rainfall between 1955 and 2009. The winter months of January and February had an increase in monthly rainfall, although winter is normally a dry season on the island. Regarding dry days, we found an annual decreasing trend, also specifically in winter. In terms of numbers of severe rainfall events described as more than 78 mm in 24 hours, 63 episodes have occurred in the San Juan area in the last decade, specifically in the 2000-2009 time frame, with an average of 6 severe events per year. The majority of the episodes occurred in summer, more frequently in August and September. These results can be seen as a clear example of the complexity of spatial and temporal of rainfall distribution over a tropical city.
climate variability; Puerto Rico; rainfall patterns; San Juan; trend analysis
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