What is ‘Apparent Temperature’?
In a few of our posts, we talk a lot about apparent temperature. What is it and how is it calculated?
While different measures have been developed in epidemiological research to quantify heat and cold exposure, a composite is a solution for extreme heat and cold exposure assessment.
We used the apparent temperature (AT) as it allows for a holistic representation of thermal comfort and perceived temperature by incorporating factors such as relative humidity and wind speed in addition to the ambient temperature.
AT is derived through a linear combination of actual temperature, vapor pressure and wind speed in metric units and interpreted in Celsius (°C), where:
\(AT = −2.7 + 1.04T + 2.0P − 0.65u\)
AT: Apparent Temperature Index in °C
T: Temperature in °C
P: Vapor pressure in kPa
u: Wind speed in m/s
References
Spangler KR, Liang S, Wellenius GA. Wet-Bulb Globe Temperature, Universal Thermal Climate Index, and Other Heat Metrics for US Counties, 2000–2020. Scientific Data. 2022 Jun 17;9(1):1–9.
Steadman RG. A Universal Scale of Apparent Temperature. J Appl Meteorol Climatol. 1984 Dec 1;23(12):1674–87.
Sheridan SC, Lee CC, Allen MJ. The Mortality Response to Absolute and Relative Temperature Extremes. Int J Environ Res Public Health [Internet]. 2019 Apr 27;16(9). Available from: