Monday, 11 January 2016
Heat index and heat wave analyses were conducted in the Caribbean. The Caribbean region is a relative tropical narrow band of land free, strongly dependent of sea surface temperature (SST). Over the past 30 years, the Caribbean region has been warming with a rate of SST increase equal to 0.018oF per year during the dry season, and 0.036oF per year during the early rainfall season. The highest warming rate (0.072oF per year) was observed in the late rainfall season. In addition, the air temperature shows a very clear increasing trend, especially since the early nineties. The air temperature changes in 1.8oF from 1948 to the present. In consequence, these warming trends may create exceptional conditions for extreme weather conditions including droughts, heat waves, and tropical cyclonic activity. This work focuses on extreme heat conditions as reflected in tendencies of heat index and heat waves. . Ground stations and the National Centers for Environmental Prediction (NCEP) Reanalysis data were used to estimate heat index and heat waves for the period of 1980-2010. The largest increasing rate of heat index was 0.11 °F/year and occurred over the Caribbean Sea and close to Venezuela. NCEP data show that Puerto Rico and Hispaniola islands exhibit the largest and significant heat-index trend of 0.06 °F/year and 0.03 °F/year, respectively, and the rest of the Greater Antilles do not exhibit heat index significant trend. NCEP data reveals a conservator trend value for the islands since most of the grids include large portion of sea water. However, NCEP data provide some notion of the heat index and heat waves. For instance, Puerto Rico based on stations data reveals a trend of 0.096 °F/year, which is larger than the value obtained from NCEP data while Dominican Republic shows an accelerated heat index increase rate of 0.08oF per year. Caribbean exhibits 5 different patterns of heat index of climatology, and the one that includes most the Greater Antilles shows a unimodal distribution with the largest pick on August and annual mean and standard deviation of 82.7°F, 5.7°F, respectively. The heat wave in the Caribbean was defined as an extreme hot event with heat index that exceed the 99.5 percentile, and this extreme hot event (>104°F) must persist for at least three consecutive days. Heat wave events were identified in the United Stated with disastrous effects. In the year 1980, more than 1,250 people died due to a strong heat wave. Although the high health risk, the heat wave events were no widely studied over the Caribbean region. The years with the largest number of extreme heat waves (>180 events) over the Caribbean were in 1983, 1998, 2005 and 2010. Especially the extreme heat waves occurred in 2010 caused a significant damage in the energy infrastructure and incidences of heat related illness. It should be noted that during the last 11 years (2003 to 2013) the Caribbean shows a persistence increment of heat waves. It was also found the duration of heat waves follows an exponential distribution with a mean of 4.1 days and standard deviation of 1.6 days. The longest heat wave occurred on Venezuela with duration of 18 days and starting on March 1, 2010.
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