Floridian Heatwaves and Extreme Precipitation. Part II: Future Climate Projections

Multi-decadal observational analysis and climate modeling efforts concur that the frequency, intensity, and duration of heatwaves will increase as the Earth’s mean climate shifts towards warmer temperatures. While the impacts and mechanisms of heatwaves have been well explored, extreme temperatures over Florida are generally understudied given its maritime climate. This paper sheds light on Floridian heatwaves by exploring 13 years of daily data from surface observations and a high-resolution WRF climate simulation for the same time frame. The characteristics of current heatwaves and future heatwaves under the RCP8.5 emissions scenario for 2070–2099 are then investigated. Results show a tripling in the frequency of heatwaves and over a six-fold increase in the mean duration of heatwaves over Florida if the present day climate threshold was applied. Floridian heatwaves could also become more intense by 4–6°C due to an increase of 3–4°C in the mean temperature in addition to a 1–2°C increase attributed to the flattening of the temperature distribution. The frequency of Floridian heatwaves could still increase even when defined using the 95th percentile of future temperature distributions (i.e., without the impact of the mean change) due to the flattened temperature distribution. Since Florida’s atmospheric boundary layer is rich in moisture and heatwaves could further increase the moisture content in the lower troposphere, the relationship between heatwaves and extreme precipitation was also explored in both the current and future climate. It was found that rainfall during a heatwave event is anomalously low, but it quickly recovers to normal within three days after the passage of a heatwave. Finally, the late 21st-century climate could witness a slight decrease in the mean precipitation over Florida, and accompanied by heavier heatwave-associated extreme precipitation events over central and southern Florida.