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Nazario D. Ramirez-Beltran, Jorge E. Gonzalez, Joan M. Castro, Moises Angeles, Eric W. Harmsen, and Cesar M. Salazar


Hourly data collected from ground stations were used to study the maximum daytime heat index H i in the Mesoamerica and Caribbean Sea (MAC) region for a 35-yr period (1980–2014). Observations of H i revealed larger values during the rainy season and smaller values during the dry season. The H i climatology exhibits the largest values in Mesoamerica, followed by the Greater Antilles and then by the Lesser Antilles. The trend in H i indicates a notable increasing pattern of 0.05°C yr−1 (0.10°F yr−1), and the trends are more prominent in Mesoamerica than in Caribbean countries. This work also includes the analysis of heat index extreme events (HIEE). Usually the extreme values of the heat index are used for advising heat warning events, and it was found that 45 HIEEs occurred during the studied period. The average duration of HIEE was 2.4 days, and the average relative intensity (excess over the threshold) was 2.4°C (4.3°F). It was found that 82% of HIEE lasted 2 or 2.5 days and 80% exhibited relative intensity of 3°C (5.4°F) or less. It was also found that the frequency of extreme events has intensified since 1991, with the highest incidences occurring in 1995, 1998, 2005 and 2010, and these years coincide with the cool phase of El Niño–Southern Oscillation (ENSO). Therefore, the occurrences of HIEE in the MAC region appear to be at least partially influenced by ENSO episodes.

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N. Hosannah, J. González, R. Rodriguez-Solis, H. Parsiani, F. Moshary, L. Aponte, R. Armstrong, E. Harmsen, P. Ramamurthy, M. Angeles, L. León, N. Ramírez, D. Niyogi, and B. Bornstein


Modulated by global-, continental-, regional-, and local-scale processes, convective precipitation in coastal tropical regions is paramount in maintaining the ecological balance and socioeconomic health within them. The western coast of the Caribbean island of Puerto Rico is ideal for observing local convective dynamics as interactions between complex processes involving orography, surface heating, land cover, and sea-breeze–trade wind convergence influence different rainfall climatologies across the island. A multiseason observational effort entitled the Convection, Aerosol, and Synoptic-Effects in the Tropics (CAST) experiment was undertaken using Puerto Rico as a test case, to improve the understanding of island-scale processes and their effects on precipitation. Puerto Rico has a wide network of observational instruments, including ground weather stations, soil moisture sensors, a Next Generation Weather Radar (NEXRAD), twice-daily radiosonde launches, and Aerosol Robotic Network (AERONET) sunphotometers. To achieve the goals of CAST, researchers from multiple institutions supplemented existing observational networks with additional radiosonde launches, three high-resolution radars, continuous ceilometer monitoring, and air sampling in western Puerto Rico to monitor convective precipitation events. Observations during three CAST measurement phases (22 June–10 July 2015, 6–22 February 2016, and 24 April–7 May 2016) captured the most extreme drought in recent history (summer 2015), in addition to anomalously wet early rainfall and dry-season (2016) phases. This short article presents an overview of CAST along with selected campaign data.

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