Applying the Excess Heat Factor algorithm to other heat indices
The Excess Heat Factor (EHF) index was developed in 2014 for use in Australian heatwave monitoring and forecasting. The index takes into account the idea that people acclimatise to their local climate, with respect to its temperature variation across latitude and throughout the year, but may not be prepared for a sudden rise in temperature above that of the recent past.
The EHF is based only on the ambient temperature, which is not the only parameter to consider for assessing the human health effects of heatwaves. For instance, relative humidity plays a key role in the estimation of heatwave magnitude in humid regions, where its severity might be underestimated if metrics are temperature-dependent only.
In this study, the EHF is determined separately for two heat stress indices that do consider the effects of humidity:
- Apparent Temperature (AT), also known as, heat index
- Wet-Bulb Globe Temperature (WBGT)

Number of heatwaves in Darwin for each month and year (2001-2015) during the hot season according to EHF-T and EHF-AT
Hot events obtained from these two indices included in the EHF algorithm are compared to the original definition of EHF, with ambient temperature solely. ERA-5 reanalysis spanning the 2001-2015 period has been utilised.
About the presentation:
This analysis was presented at the Australian Meteorological and Oceanographic Society Annual Meeting and the International Conference on Tropical Meteorology and Oceanography (AMOS-ICTMO 2019), held in Darwin from 11-14 June 2019. The results from EHF-WBGT were excluded from the slides in order to make a smoother presentation.
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