Limited Role of Absolute Humidity in Intraurban Heat Variability

Journal Article · 30 November 2023 · Journal of Applied Meteorology and Climatology

DOI: https://doi.org/10.1175/JAMC-D-23-0096.1 · OSTI ID:2229791

Waugh, Darryn W.  ^[1]; Zaitchik, Benjamin ^[1]; Scott, Anna A. ^[1]; Ibsen, Peter C. ^[2]; Jenerette, G. Darrel ^[3]; Schatz, Jason ^[4]; Kucharik, Christopher J. ^[5]

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1. a Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland
2. b Geosciences and Environmental Change Science Center, U.S. Geological Survey, Denver, Colorado
3. c Department of Botany and Plant Sciences, University of California, Riverside, Riverside, California
4. d SkyTruth, Santa Fe, New Mexico
5. e Nelson Institute Center for Sustainability and the Global Environment, University of Wisconsin–Madison, Madison, Wisconsin, f Department of Agronomy, University of Wisconsin–Madison, Madison, Wisconsin

Abstract Monitoring and understanding the variability of heat within cities is important for urban planning and public health, and the number of studies measuring intraurban temperature variability is growing. Recognizing that the physiological effects of heat depend on humidity as well as temperature, measurement campaigns have included measurements of relative humidity alongside temperature. However, the role the spatial structure in humidity, independent from temperature, plays in intraurban heat variability is unknown. Here we use summer temperature and humidity from networks of stationary sensors in multiple cities in the United States to show spatial variations in the absolute humidity within these cities are weak. This variability in absolute humidity plays an insignificant role in the spatial variability of the heat index and humidity index (humidex), and the spatial variability of the heat metrics is dominated by temperature variability. Thus, results from previous studies that considered only intraurban variability in temperature will carry over to intraurban heat variability. Also, this suggests increases in humidity from green infrastructure interventions designed to reduce temperature will be minimal. In addition, a network of sensors that only measures temperature is sufficient to quantify the spatial variability of heat across these cities when combined with humidity measured at a single location, allowing for lower-cost heat monitoring networks. Significance Statement Monitoring the variability of heat within cities is important for urban planning and public health. While the physiological effects of heat depend on temperature and humidity, it is shown that there are only weak spatial variations in the absolute humidity within nine U.S. cities, and the spatial variability of heat metrics is dominated by temperature variability. This suggests increases in humidity will be minimal resulting from green infrastructure interventions designed to reduce temperature. It also means a network of sensors that only measure temperature is sufficient to quantify the spatial variability of heat across these cities when combined with humidity measured at a single location.

• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0023217
• OSTI ID: 2229791
• Journal Information: Journal of Applied Meteorology and Climatology, Journal Name: Journal of Applied Meteorology and Climatology Journal Issue: 12 Vol. 62; ISSN 1558-8424
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English