MaRTy for Kids: Adapting Biomet Equipment to Capture the Heat Exposure of Children

The methods and equipment for the quantification of outdoor thermal comfort conditions have evolved over the past few years. There is consensus about the use of 3 net radiometers as the best way to quantify the mean radiant temperature (MRT) outdoors and MaRTy has been a popular implementation of this concept, with a mobile approach. MaRTY is a mobile biometeorological instrument platform capable of measuring air temperature, humidity, wind speed and direction, GPS coordinates and MRT using data captured in six directions by six solar and six infrared radiometers. These parameters are used to compute the local thermal comfort conditions, simulating the way the human body experiences heat. However, the weather station is commonly placed at 1.5 m and the net radiometers at 1 m above the ground, which describes the conditions relevant to a standing adult but not for a child or a sitting person.

Here, we present a modified setup that allows for the measurement of the air temperature, dew point temperature and wind speed at 0.3 m, 1.5 m, and 1.8 m, and the mean radiant temperature at 0.5 m and 1 m. The latter allows for the measurement of the MRT with different view factors to portions of the ground and of artificial/natural shade, which is particularly relevant for children at playgrounds, where there is not a consistent land cover and shading over a large area. Our measurements show that during weak wind conditions, the air temperature at 0.30 m can be even 1 C higher than at 1.5 or 1.8 m. The wind speed at 0.30 m is also lower than at 1.5 m, as is the relative humidity. These measurements are consistent with the theory of boundary layers near the surface, and they quantify different heat stress exposure for children than for their standing parents/guardians.