Using Mean Radiant Temperature to Evaluate Microclimatic Variability in Two Sonoran Desert Educational Landscapes

In the Sonoran Desert region of Arizona, educational landscapes such as botanical gardens and zoos provide context for and education about both local and global biodiversity for the public. These landscapes also serve as vital green spaces as outdoor venues for a diverse array of cultural events. As the global climate warms, these outdoor biodiversity learning landscapes may increasingly present the hazard of extreme heat for diverse user groups, including visitors, staff, and volunteers. The staff at these institutions include a large outdoor workforce of horticultural, zoological, and maintenance workers, and many of the volunteers are older adults who are at increased risk of negative health outcomes from their time spent in extreme heat. Visitors to these landscapes include young children and tourists visiting from cooler climates, all of whom may be more vulnerable to adverse health outcomes due to extreme heat, owing to their age and lack of acclimatization. This research aims to understand the summer microclimates that currently exist within these landscapes, and how landscape design can improve or worsen microclimatic conditions in terms of heat exposure for users. During the summer of 2024, midday and evening transects of common visitor routes at two Sonoran Desert educational landscapes were conducted using the MaRTy biometeorological cart, a mobile weather station equipped with net radiometers that can effectively measure mean radiant temperature (MRT) using the six-directional method. Simultaneous to the MaRTy transects, Kestrel 5400 Heat Stress Trackers were placed on stationary tripods at strategic locations representing the range of landscape design typologies users are likely to spend time in. The design elements evaluated include paving materials, type of vegetation, type of shade, proximity to water features, and employment of outdoor cooling equipment such as evaporative coolers, fans, and misters. The results suggest that landscape design features and outdoor cooling equipment can significantly alter the outdoor microclimate in terms of MRT, and if placed appropriately could reduce user exposure to extreme heat in these educational landscapes.