Levels of Heatwave Severity Utilising Climatology of Intensity
The 85th percentile of the cumulative distribution function of daily heatwave intensity forms the transition from frequently observed low intensity heatwaves to rarer, high intensity heatwaves. Transition in scale of heatwave impact is demonstrated in health impact case studies.
Climatologically derived severe heatwave intensity thresholds are mapped to charts of heatwave intensity illustrating areas of low, severe and extreme heatwave intensity offering spatial views of relative impact. These mapped severity levels are simple to interpret and link with mitigation measures for government and civil organisations or the public.
Severe and extreme heatwave events are linked to soil dryness produced by drought (significant rainfall deficit). Further insight into heat health impact is considered where more common, low intensity heatwaves may be associated with humid air masses, whilst severe and extreme heatwave intensity is increasingly associated with dry air. Commonly used adaptive strategies for low intensity humid heatwaves can have unintended consequences when deployed during high intensity (dry) heatwaves, particularly amongst vulnerable populations.