Mechanisms-Informed Projections of Chronic Humid Heat Hazard in South Florida

Chronic humid heat, characterized by extended periods of time (over 90 days) at dangerous heat hazard values, is an increasingly dangerous hazard that has been worsening in recent decades. It poses a particular threat to the tropics and subtropics, where dangerous heat days are projected to constitute a majority of the year by 2100. This study makes high resolution regional projections of the future chronic humid heat hazard in South Florida using high resolution climate models, in particular MESACLIP and the HighResMIP models. We employ a mechanism informed approach, utilizing previously established seasonally varying drivers of heat hazard in South Florida, dry season sea surface temperature variability and wet to establish confidence in model projections. This is accomplished by assessing if models reproduce the observed relationships between these drivers and regional heat metrics. Through this approach, we evaluate the projected changes in temperature, humidity, heat index, and wet bulb temperature in the region both on multidecadal and interannual timescales. Our results provide mechanisms informed high resolution projections of temperature and physiologically relevant heat metrics for the South Florida region, with implications for climate adaptation and planning.