Advanced human heat exposure sensing using two cylinder anemometer and radiometer: introducing CARla

Area of Science:

• Environmental Science
• Biometeorology
• Urban Planning

Background:

• Extreme heat poses significant health risks, often exacerbated by radiative heat exposure.
• Current methods for measuring radiative heat are often expensive, inaccurate, or not user-friendly.
• Hyperlocal biometeorological data is essential for effective heat action planning and urban design.

Purpose of the Study:

• To develop an affordable, accurate, and user-friendly sensor for measuring human exposure to extreme heat.
• To quantify both wind speed and total absorbed radiation, key components of thermal comfort.
• To improve heat action planning, emergency responses, and urban design through better biometeorological data.

Main Methods:

• Development of a two-cylinder anemometer and radiometer (CARla) with unheated and heated gray components.
• Optimization of CARla's geometrical parameters to minimize measurement errors.
• Field experiments conducted at 15 outdoor sites in Tempe, Arizona, during a heatwave.
• Comparison of CARla measurements with standard 3-way net radiometers and ultrasonic anemometers.

Main Results:

• CARla accurately measured mean radiant temperature (MRT) with an average error of 1.3 ± 2.2 °C across a wide range (20-75 °C).
• Wind speed measurements from CARla showed an average difference of -0.05 ± 0.36 m·s⁻¹ compared to ultrasonic anemometers.
• The sensor's spectral properties match standard absorptivity used in MRT calculations.
• CARla demonstrated significant improvements over other low-cost radiometers.

Conclusions:

• CARla provides a cost-effective and accurate solution for characterizing human exposure to extreme heat.
• The sensor's ability to measure both wind speed and radiation enhances its utility for hyperlocal biometeorological assessments.
• Integration with an Arduino logger creates an accessible tool for public health and urban planning initiatives.