Intense summer heat fluxes in artificial turf harm people and environment

Artificial turf (AT) sports fields have increasingly replaced natural turf (NT). High AT material-cum-air temperature incurs heat-stress impacts on athletes, demanding better understanding of thermal regimes vis-à-vis weather conditions. Adjacent AT and NT sites in humid-tropical Hong Kong were studied. Four radiant-energy components (direct-solar, reflected-solar, sky-thermal, ground-thermal) and five temperature levels (150, 50 and 15 cm, turf-surface, substrate) were monitored in replicate, for three summer weather conditions (sunny, cloudy, overcast). Inter-site differences are attributed to lower AT albedo, admitting more shortwave and emitting more longwave radiant energy. Drastic decline in solar fluxes contrasts with terrestrial fluxes which remain intense. AT materials, with low specific heat and moisture and scanty evapotranspiration, induce fast warming and cooling with little time lag to synchronize with insolation rhythm. On sunny day, AT turf-surface, heated to 72.4 °C comparing with NT at 36.6 °C, dissipates heat by conduction and convection to near-ground air and by strong ground-thermal emission. Exceeding the heat-stress threshold most of the time, AT cools quickly from late afternoon for heat-safe use soon after sunset. On cloudy day, subdued AT heating allows earlier cooling in late afternoon. Both sites are heat-safe on overcast day. The findings can optimize game scheduling to prevent heat-related injuries.