It’s Not the Heat, It’s the Humidity…and Wind and Solar: Developing and Validating Heat Exposure Products Using the U.S. Climate Reference Network

NOAA’s National Centers for Environmental Information (NCEI) oversees the observations of the United States Climate Reference Network (USCRN). This network consists of 114 sites across the conterminous 48 states, with additional sites in Alaska and Hawaii. Stations are sited and installed in areas ideally to have stable land cover and use conditions for several decades to come. At each site a suite of meteorological parameters are monitored, including triple redundancy for primary air temperature variables. Other variables recorded at USCRN sites include solar radiation, relative humidity, and 1.5 meter wind speed. Because these variables can play a role in heat exposure, it makes sense to explore, develop, and test heat related indices using high resolution USCRN data.

Using data at hourly and 5-minute resolution, three separate heat exposure indicators are developed. The first is the heat index (HI), which uses heat and humidity information, and is commonly used in National Weather Service products. The second is Apparent Temperature (AT), defined by Steadman (1984), and uses temperature, relative humidity, and wind to differentiate between indoor and outdoor exposure. The third is Wet Bulb Globe Temperature (WBGT), which is commonly used in industry, sports, and the military to determine outdoor human exposure. WBGT incorporates air temperature, wet bulb temperature, and black globe temperature, the latter requiring solar radiation information. The 5-minute values of these variables can be accumulated to better understand the total exposure to the heat event.This paper will provide climatological information of each metric at USCRN sites, look at case studies of recent extreme heat events, and validate results using nearby ECONet data provided by the North Carolina State Climate Office.