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Evaluation and development of a Southeast US heat vulnerability index using a wet bulb globe temperature approach

The 4th US National Climate Assessment (2018) identified extreme heat as one of the  Southeast’s most pressing human health climate risks in urban areas and is exacerbated by  an aging population, warming climate, and rapid urbanization. Much of the work in the  National Climate Assessment on extreme heat is based on apparent temperature (e.g., heat  index) extremes, which largely do not measure the physiological impact of heat stress on  the human body. Furthermore, at-risk groups (e.g., low income communities and elderly  populations) may lack sufficient cooling or have underlying health conditions. These  groups are especially threatened by warm and humid nighttime temperatures, neither of  which are measured appropriately by traditional methods. For human health applications,  wet bulb globe temperature (WBGT) is a better measure of how heat affects humans, and is  currently used in operational settings (e.g., military and athletics). However, WBGT has not  been used widely in observational climate studies, due to the lack of observational datasets.  Further complicating matters, many methods exist for calculating WBGT, some of which  may not be suitable for the Southeast US.

Broader Impacts and Relevance to the Competition & NOAA’s Climate Program Office 

Heat is the deadliest weather-related hazard.  While we propose a rigorous evaluation of  WBGT, we recognize the limitations of the measure when interfacing with the public.  WBGT values are not intuitive, and a fatal WBGT (i.e., 94 ̊F) may be perceived as safe when  assumed to be on par with traditional heat index values. In response to the NOAA Climate  Program Office competition for MAPP: New Climate Monitoring Approaches and Products for  Areas of Climate Risk, we propose to evaluate WBGT formulas and calculate climatologies  and trends across the Southeast US, with a focus on urbanized and “seasonally-urban”  areas. Per the solicitation, we will develop a new climate monitoring product. This product  will be a Heat Vulnerability Index (HVI) based off WBGT analyses with an exposure,  sensitivity, and adaptive capacity component. We will test the HVI with four National  Weather Service Weather Forecast Offices and one Military partner.

We will develop a real-time HVI monitor, similar to the US Drought Monitor, for operational  use. NOAA’s Climate Program Office has identified extreme heat in urban regions as an area  of focus. Our results will help support NWS’ Weather Ready Nation initiative by identifying areas of vulnerability useful for successful prediction and preparation of extreme heat  events. Furthermore, this index can be used in future National Climate Assessment  activities as a more accurate snapshot of extreme heat in the Southeast US.

We will address the project goals through five tasks: (1) Gather observations and evaluate  WBGT estimation formulas; (2) Develop WBGT climatologies and perform trend analysis;  (3) Build a WBGT based Heat Vulnerability Index (HVI); (4) Test gridded WBGT data and the HVI with project partners; (5) Participation on MAPP Task Force.

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