Excess Heat and Excess Cold Factors: Establishing a unified duration-intensity metric for monitoring hazardous temperature conditions in North America

Introduction to the problem: Among weather-related hazards, extreme heat is one of the leading causes of death worldwide, and in future decades a changing climate is likely to disproportionally increase the frequency of extreme heat events, leading to a greater potential for heat-related mortality in the future. Extreme low temperatures can also lead to increased mortality, and as recent events have shown, may not disappear entirely in a  warming world. There is a challenge in assessing extreme temperature events spatially, as human vulnerability is location-dependent, and thus, no specific temperature values are universally relevant for such an analysis. This concern has led to myriad ways in assessing the occurrence of extreme temperature events. 

Rationale and objectives: The overarching objective of this proposal is focused on the development of excess temperature event identifications that are based on systematic percentile thresholds of apparent temperature across North America, which also incorporate the acclimatization of the population to prior conditions. These events will include both hot and cold, as well as relative hot and relative cold, where relative refers to the time of year. These events will be developed into prospective monitoring products. The robustness of these products will be assessed through different data sets. Using the event definitions that are developed, we then aim to transition these to become operational monitoring products and real-time forecast products.  

Summary of the work to be completed: Spanning North America, we will first calculate daily values of multiple extreme temperature products for each grid cell across four different reanalysis products, as well as the ISD historical station observation network. We will analyze the historical frequency, duration, spatial extent, and population impacted by these events, and cross-validate the results between the station data and the reanalyses. We will then work with our NOAA collaborator and consult with an advisory board of likely end users to transition all research products above into real-time monitoring products. We will also set up a webpage for real-time forecasting of all products for up to 60-day lead times.  

Relevance to the competition and NOAA: The proposed research will develop new daily-scale monitoring products that identify absolute and relative extreme temperature events. These products will be used to help monitor the occurrence, duration, areal extent and total population impacted by extreme temperatures. A standard set of products can unify and simplify information used by local National Weather Service offices and public health leaders to issue excessive heat and cold warnings across climatologically diverse areas of North America. The competition specifically calls for products that monitor extreme heat, that may be able to fill gaps in the National Climate Assessment and the USGCRP  Indicators Platform, and those that utilize the underused reanalysis datasets and operational climate analyses – all of which are objectives that this research would meet.