Trends in Total Rainfall, Heavy Rain Events and Number of Dry Days in San Juan-Puerto Rico (1955-2009)


Trends in Total Rainfall, Heavy Rain Events and Number of Dry Days in San Juan-Puerto Rico (1955-2009)

Pablo A. Méndez-lázaro, Alejandro Nieves-santiango, Julieanne Miranda-bermúdez

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 mud/landslide, meteorological phenomena as hurricanes, risks/hazards including severe storms and flooding, and health effects as vector-borne diseases, and waterborne diseases. Therefore, in the context of global change, research on the behavior of rainfall patterns and its variations, present a challenge to the scientific community. The main objective of this research is to analyze recent trends in precipitation using historical data from weather stations in the San Juan Metropolitan Area in Puerto Rico and its relationship with regional and global climate variations.

All stations showed positive trends of increasing annual rainfall between 1955 and 2009. On the other hand, the winter months of January and February exhibited a increase in monthly rainfall. Winter months are normally dry season months on the island. Regarding dry days, we found an annual decreasing trend specifically also in winter. In terms of numbers of severe rainfall events described as >78mm/24hrs, 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, yet more frequently in August and September. These results can be seen as clear example of the complexity of spatial and temporal of rainfall distribution over a tropical city.

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