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.